IMPORTANT INFORMATION REGARDING PHENO 2021 IN LIGHT OF THE COVID-19 PANDEMIC
Due to the ongoing COVID-19 pandemic, Pheno 2021 will be host virtually. The full details of this virtual meeting will be made available soon. Registration for this virtual symposium will be free. The talk schedule will roughly follow the planned schedule as though its a physical meeting and will be held May 24 to May 26. We would like to encourage you to register and submit an abstract for a parallel talk. We hope to see you online in May!
PROGRAM
The 2021 Phenomenology Symposium will be held May 24-26, 2021 at the University of Pittsburgh. It will cover the latest topics in particle phenomenology and theory plus related issues in astrophysics and cosmology.
Registration deadline: May 23, 2021
Abstract submission deadline for parallel talks: May 3, 2021 (We do not accept abstracts anymore.)
Confirmed plenary speakers and topics:
Mini-Reviews: (1). Hartmut Wittig (Johannes Gutenberg University Mainz), The SM expectation for muon g-2. (2). David Shih (Rutgers University), Anomaly Detection with ML.
Parallel session extension:
Due to the large number of contributed talk submissions, parallel sessions have been extended to include Wednesday afternoon from 2:00pm - 6:30pm.
FORUM ON EARLY CAREER DEVELOPMENT
Invited Speakers: Julia Gonski (Columbia Univ.), Sara Simon (Fermilab), and Midhat Farooq (APS)
"Physics Career Paths: Finding Success in Academia, Industry, and Beyond"
May 24, 1:00-2:00 PM
The forum will consist of an overview of career paths for physicists followed by time for questions from the participants.
VIRTUAL COCKTAIL HOUR, AWARDS CEREMONY, AND HISTORY OF PHENO
As is a Pheno tradition, we will have a social hour and awards ceremony after the parallel sessions on Tuesday, May 25 at 6:45 PM EDT. Though we cannot share a drink together, we encourage you to join with your favorite beverage in hand! Award recipients will not be notified in advance, so make sure to join to learn if you won one!
As a special treat, this year we will welcome Professor Vernon Barger from the University of Wisconsin - Madison to share with us the history and his reminiscences of the Phenomenology Symposia.
PHENO 2021 ORGANIZERS: Ayres Freitas, Joni George, Tao Han (chair), Adam Leibovich, Cédric Weiland, Benjamin Carlson, Brian Batell, Akshay Ghalsasi and Keping Xie.
PHENO 2021 PROGRAM ADVISORS: Vernon Barger, Lisa Everett, Kaoru Hagiwara, JoAnne Hewett, Tae Min Hong, Arthur Kosowsky, James Mueller, Vittorio Paolone, Tilman Plehn, Vladimir Savinov, Xerxes Tata, Andrew Zentner, and Dieter Zeppenfeld.
More information to come.
https://pitt.zoom.us/j/93951025550
https://pitt.zoom.us/j/93951025550
We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The Z_N symmetry proposed by Hook, with N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered and the associated phenomenology is studied in detail.
On a second step, we show that dark matter can be accounted for by this extremely light axion. This includes the first proposal of a ``fuzzy dark matter'' QCD axion. A novel misalignment mechanism occurs -- trapped misalignment-- due to the peculiar temperature dependence of the Z_N axion potential, which in some cases can also dynamically source the recently proposed kinetic misalignment mechanism.
The resulting universal enhancement of all axion interactions relative to those of the canonical QCD axion has a strong impact on the prospects of ALP experiments such as ALPS II, IAXO and many others. For instance, even Phase I of Casper Electric could discover this axion.
Based on 2102.00012 and 2102.01082.
The Standard Model (SM) suffers from five shortcomings: Dark Matter, Neutrino masses and mixing, Baryon asymmetry, Strong CP-Problem and Inflation. The latter is regarded as the seeds for structure formation. In this talk, we introduce an inflationary $\nu$DFSZ-type axion model which is dubbed 2hdSMASH (Two-Higgs-Doublet SM * Axion * Seesaw * Higgs-Portal-Inflation). 2hdSMASH aims at giving a complete and unified picture of the universe evolution from the inflationary epoch to today. In particular, we focus on parameter constraints coming from the inflationary epoch which provide in the low energy limit phenomenologically viable scalar masses that can be tested at LHC, HL-LHC or future colliders
We consider supersymmetric extensions of DFSZ type axion models with the field content of the MSSM plus some extra vectorlike quark and lepton supermultiplets that simultaneously give a solution to the $\mu$ problem and the strong CP problem. The extra vectorlike content is chosen such that the perturbative gauge coupling unification is maintained. We identify Peccei-Quinn (PQ) symmetry that is protected to a high degree of accuracy as an accidental symmetry emerging from anomaly-free discrete symmetries with or without a discrete version of the Green-Schwarz mechanism. The PQ symmetry is spontaneously broken with two gauge singlets acquiring intermediate scale vacuum expectation values giving rise to a high-quality invisible axion and a $\mu$ term around the TeV scale. After the PQ breaking the axion potential typically acquires more than one inequivalent degenerate minima leading to a cosmological domain wall problem. We therefore pay special attention to the models that evade this problem.
We propose a $SU(5) \times U(1)_X \times U(1)_{PQ}$ model, where $U(1)_X$ is the generalization of the $B-L$ (baryon minus lepton number) gauge symmetry and $U(1)_{PQ}$ is the global Peccei-Quinn (PQ) symmetry. There are four fermions families in $\bf{{\overline 5}} + \bf{10}$ representations of $SU(5)$, a mirror family in $\bf{5}+\bf{{\overline {10}}}$ representations, and three $SU(5)$ singlet Majorana fermions. The $U(1)_X$ related anomalies all cancel in the presence of the Majorana neutrinos. The $SU(5)$ symmetry is broken at $M_{GUT} \simeq (4-7)\times 10^{15}$ GeV and the proton lifetime $\tau_p$ is estimated to be well within the expected sensitivity of the future Hyper-Kamiokande experiment, $\tau_p \lesssim 1.3 \times 10^{35}$ years. The $SU(5)$ breaking also triggers the breaking of the PQ symmetry, resulting in axion dark matter (DM), with the axion decay constant $f_a$ of order $M_{GUT}$ or somewhat larger. The CASPEr experiment can search for such axion DM candidates. With the identification of the $U(1)_X$ breaking Higgs field with the inflaton field, we implement low scale inflection-point inflation with $H_{inf} < 10^9 $ GeV which successfully resolve the cosmologically fatal axion domain wall, axion DM isocurvature and $SU(5)$ monopole problems. The vectorlike fermions in the model are essential for achieving a successful unification of the SM gauge couplings as well as the phenomenological viability of both axion DM and inflation scenario.
We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then integrate out heavy magnetic monopoles using the Schwinger proper time method. We find that the model discussed yields axion couplings to the Standard Model which are drastically different from the ones calculated within the KSVZ/DFSZ-type models, so that large part of the corresponding parameter space can be probed by various projected experiments. Moreover, the axion we introduce is consistent with the astrophysical hints suggested both by anomalous TeV-transparency of the Universe and by excessive cooling of horizontal branch stars in globular clusters. We argue that the leading term for the cosmic axion abundance is not changed compared to the conventional pre-inflationary QCD axion case for axion decay constant $f_a > 10^{12}~\text{GeV}$.
A large flux of axion-like particles can be produced in the solar core. While the majority of these particles will have high velocities and escape the Sun’s gravitational pull, a small fraction of low-velocity particles will become trapped on bound orbits. Over time, an appreciable density of slow-moving axions can accumulate in this “solar basin.” Their subsequent decay to two photons provides a distinct observational signature. I will present an ongoing analysis using the NuSTAR X-ray telescope to search for the decay products of keV-scale axions trapped in the solar basin.
We show that axion-like particles that the only couple to invisible dark photons can generate visible B-mode signals around the reionization epoch. The axion field starts rolling shortly before reionization, resulting in a tachyonic instability for the dark photons. This generates an exponential growth of the dark photon quanta sourcing both scalar metric modes and gravitational waves that leave an imprint on the reionized baryons. The tensor modes modify the cosmic microwave background (CMB) polarization at reionization, generating visible B-mode signatures for the next generation of CMB experiments for parameter ranges that satisfy the current experimental constraints.
This talk discusses new techniques to detect signatures potentially originating from long-lived particles in the CMS detector, presents recent results from such searches in CMS using the full Run-II data-set of the LHC, and discusses prospects for Run-III
Abstract: Various models of physics Beyond the Standard Model lead to signatures with long-lived particles, such that the decay of the new particle is at a significant distance from the collision point. These striking signatures provide interesting technical challenges due to their special reconstruction requirements as well as their unusual backgrounds. This talk will present recent results in searches for new, long-lived particles using ATLAS Run 2 data.
Triggering long-lived particles (LLPs) at the first stage of the trigger system is very crucial in LLP searches to ensure that we do not miss them at the very beginning. The future High Luminosity runs of the Large Hadron Collider will have an increased number of pile-up events per bunch crossing. There will be major upgrades in hardware, firmware and software sides, like tracking at level-1 (L1). The L1 trigger menu will also be modified to cope with pile-up and maintain the sensitivity to physics processes. In our study we found that the usual level-1 triggers, mostly meant for triggering prompt particles, will not be very efficient for LLP searches in the 140 pile-up environment of HL-LHC, thus pointing to the need to include dedicated L1 triggers in the menu for LLPs. We consider the decay of the LLP into jets and develop dedicated jet triggers using the track information at L1 to select LLP events. We show in our work that these triggers give promising results in identifying LLP events with moderate trigger rates.
Models with dark showers represent one of the most challenging possibilities for new physics at the LHC. One of the most difficult examples is a novel collider signature called a Soft Unclustered Energy Pattern (SUEP), which can arise in certain BSM models with a hidden valley sector that is both pseudo-conformal and strongly coupled. Large-angle emissions are unsuppressed during the showering process, and if the hidden sector hadrons decay hadronically and promptly back into the Standard Model, the result is a high-multiplicity shower of SM final state particles that possess more democratically distributed energies and a much higher degree of isotropy than typically seen in QCD jets. This signature presents significant challenges to trigger on and search for, due to the lack of isolated hard objects to identify in the detector. We outline an analysis strategy to look for SUEP produced by exotic decays of the Higgs boson, using both conventional cuts on event-level observables and anomaly detection methods from machine learning. We find that for some regions of dark shower parameter space, data from the HL-LHC could be used to exclude branching ratios of Higgs decay to SUEP down to a few percent.
Models with dark showers represent one of the most challenging possibilities
for new physics at the LHC. The most difficult to detect variety of
these models is so-called Soft Unclustered Energy Pattern (SUEP). This signature presents significant challenges to trigger on and search for, in part due to the lack of isolated hard objects to identify in the detector as well as the large amount of QCD background in the relevant SUEP phase space.
Signatures like this appear in models with a hidden valley sector that is both
pseudo-conformal and strongly coupled. In such models large-angle emissions are unsuppressed during the showering process. If the hidden sector hadrons decay promptly back into Standard Model hadrons, the result is a high-multiplicity shower of SM final state particles with a more democratic distribution of energies and a much higher degree of isotropy than typically seen in QCD jets.
We outline an analysis strategy to look for SUEP produced by exotic decays of the Higgs boson, using both conventional cuts on event-level observables as well as supervised and unsupervised machine learning anomaly detection methods. We identify the regions of dark shower parameter space which yield SUEP-like Higgs decays and discuss different exclusion methods for various benchmarks. We discuss how search strategies differ depending on the details of the signal generated in different regions of parameter space.
The search for long-lived particles (LLP) at the LHC can be improved with timing information. If the visible decay products of the LLP form jets, the arrival time is not well-defined. In this talk, I will discuss possible definitions and how they are affected by the kinematics of the underlying parton-level event.
Many BSM models predict long-lived particles (LLPs) which are generally difficult to detect at existing colliders. We have explored the potential of a future far detector at Belle II, named GAZELLE. For that, we have investigated three models that predict LLPs with different production mechanisms. In this talk, I will compare the projections of finding these LLPs at Belle II or GAZELLE. Due to Belle II's excellent sensitivity to LLPs, we find little extra gain in building a far detector like GAZELLE.
https://pitt.zoom.us/j/91032362960
Massive field excitations during the inflationary era, imprinted on cosmological correlation functions, have been studied as a unique opportunity to probe heavy degrees of freedom beyond the terrestrial colliders. In the simplest inflationary models, any such cosmological collider signal is exponentially suppressed for fields much heavier than the inflationary Hubble scale, limiting the potential reach of such new physics searches. We show that existence of high-frequency classical oscillations can resonantly enhance heavy field signals. In particular, we study two concrete examples of such classical oscillations: (i) coherent oscillation of another massive field, classically excited due to a sharp feature in a generic multi-field scenario, and (ii) sub-dominant oscillations of the inflaton itself, as a result of periodic features on the inflationary potential.
Current measurements of Standard-Model parameters suggest that the electroweak vacuum is metastable. This metastability has important cosmological implications because large fluctuations in the Higgs field could trigger vacuum decay in the early universe. For the false vacuum to survive, interactions which stabilize the Higgs during inflation—e.g., inflaton-Higgs interactions or non-minimal couplings to gravity—are typically necessary. However, the post-inflationary preheating dynamics of these same interactions could also trigger vacuum decay, thereby recreating the problem we sought to avoid. This dynamics is often assumed catastrophic for models exhibiting scale invariance since these generically allow for uninterrupted growth of fluctuations. In this talk, we examine the dynamics of such "massless preheating" scenarios and show that the competing threats to metastability can nonetheless be balanced to ensure viability. We find that fully accounting for both the backreaction from particle production and the effects of perturbative decays reveals a large number of disjoint "islands of (meta)stability" over the parameter space of couplings. Ultimately, the interplay among Higgs-stabilizing interactions plays a significant role, leading to a sequence of dynamical phases that effectively extend the metastable regions to large Higgs-curvature couplings.
We consider a non-Abelian dark SU(2)D model where the dark sector couples to the Standard Model (SM) through a Higgs portal. We investigate two different scenarios of the dark sector scalars with Z2 symmetry, with Higgs portal interactions that can introduce mixing between the SM Higgs boson and the SM singlet scalars in the dark sector. We utilize the existing collider results of the Higgs signal rate, direct heavy Higgs searches, and electroweak precision observables to constrain the model parameters. The SU(2)D partially breaks into U(1)D gauge group by the scalar sector. The resulting two stable massive dark gauge bosons and pseudo-Goldstone bosons can be viable cold dark matter candidates, while the massless gauge boson from the unbroken U(1)D subgroup is a dark radiation and can introduce long-range attractive dark matter (DM) self-interaction, which can alleviate the small-scale structure issues. We study in detail the pattern of strong first-order phase transition and gravitational wave (GW) production triggered by the dark sector symmetry breaking, and further evaluate the signal-to-noise ratio for several proposed space interferometer missions. We conclude that the rich physics in the dark sector may be observable with the current and future measurements at colliders, DM experiments, and GW interferometers.
We study the evolution of cosmological domain walls in models with asymmetric potentials. Our research goes beyond the standard case of spontaneous breaking of an approximate symmetry. The time after which the network will decay depends on the difference of values of the potential in minima, its asymmetry around the maximum separating minima and the bias of initial distribution. Using numerical lattice simulations we determine relative importance of these factors on decay time of networks for generic potentials. We find that even very small departures from the symmetric case lead to rapid decay of the domain wall network. As a result creation of a long lasting network capable of producing observable gravitational wave signals is much more difficult than previously thought.
Hidden naturalness offers an exciting framework for alleviating the Higgs hierarchy problem. But because the models within this framework face few constraints from collider searches, there is strong motivation to study their cosmological signatures, an area that has remained mostly unexplored. One of the simplest models that can be studied in this framework is the mirror twin Higgs (MTH) model, a model that contains a near-mirror copy of the SM. Cosmologically, the MTH model is quite complex, containing new sources of free-streaming radiation, interacting radiation, and interacting dark matter. In this talk I will discuss how cosmological datasets, including the CMB temperature and polarization power spectra as measured by the Planck collaboration, constrain the parameter space of the MTH model. In addition, I will also show how this model may help in ameliorating the tensions in the cosmological datasets, specifically those related to the sigma8 and H0 measurements.
Taking the minimalistic approach, within MSSM, we propose the model of inflation in which the inflaton field is a scalar component of the MSSM state(s).
Two cases will be discussed, which (both) turn out to be very predictive. The inflationary phase is fully governed by the MSSM Yukawa superpotential couplings. The values of the scalar spectral index and the tensor-to-scalar ratio are predicted to be ns≃0.966 and r=0.00118. The postinflation reheating of the Universe proceeds by the decay of the inflaton with the reheating temperature around 10 thousands TeV.
Some phenomenological implication will be also discussed.
We discuss phenomenological viability of a novel inflationary model in the minimal gauge mediated supersymmetry breaking scenario.
In this model, cosmic inflation is realized in the flat direction along the messenger supermultiplets and a natural dark matter candidate is the gravitino from the out-of-equilibrium decay of the bino-like neutralino at late times, which is called the superWIMP scenario.
The produced gravitino is warmish and can have a large free-streaming length; thus the cusp anomaly in the small scale structure formation may be mitigated.
We show that the requirement of the Standard Model Higgs boson mass to be $m_{h^0}=125.1$ GeV gives a relation between the spectrum of the cosmic microwave background and the messenger mass $M$.
We find, for the e-folding number $N_e=60$, the Planck 2018 constraints (TT, TE, EE+lowE+lensing+BK15+BAO, 68\% confidence level) give
$M > 3.64\times 10^7$ GeV.
The gravitino dark matter mass is $m_{3/2} < 5.8$ GeV and the supersymmetry breaking scale $\Lambda$ is found to be in the range
$(1.28-1.33)\times 10^6$ GeV.
Future CMB observation is expected to give tighter constraints on these parameters.
Searches in CMS for dark matter particles, mediators, and dark sector extensions will be presented. Various final states, topologies, and kinematic variables are explored utilizing the full Run-II data-set collected at the LHC.
The presence of a non-baryonic Dark Matter (DM) component in the Universe is inferred from the observation of its gravitational interaction. If Dark Matter interacts weakly with the Standard Model (SM) it could be produced at the LHC. The ATLAS experiment has developed a broad search program for DM candidates, including resonance searches for the mediator which would couple DM to the SM, searches with large missing transverse momentum produced in association with other particles (light and heavy quarks, photons, Z and H bosons) called mono-X searches and searches where the Higgs boson provides a portal to Dark Matter, leading to invisible Higgs decays. The results of recent searches on 13 TeV pp data, their interplay and interpretation will be presented. Prospects for HL-LHC will also be discussed.
If the dark sector contains multiple components with similar quantum numbers which communicate with the visible sector only through a mediator, then this mediator also generically gives rise to dark-sector decays, with heavier dark components decaying to lighter ones. Successive such decays lead to extended decay chains in which visible matter is also produced at every decay step. In this talk, I explore the collider consequences of such decay chains in the case in which the mediator couples to the quark sector of the Standard Model. I discuss the properties of the multi-jet signatures that arise in such scenarios and show that within relatively large regions of parameter space, these signatures are not excluded by existing monojet and multi-jet searches. Such decay cascades therefore represent a potential discovery route for multi-component dark sectors at current and future colliders.
In this paper, we point out a novel signature of physics beyond the Standard Model which could potentially be observed both at the High-Luminosity LHC (HL-LHC) and at future colliders. We call such a signature a "tumbler." In this talk, I discuss the prospects for observing tumbler signatures at the HL-LHC, taking into account the enhanced timing capabilities afforded by the upgraded LHC detectors. We not only find that a statistically significant number of tumbler events could potentially be observed at the HL-LHC, but also find that meaningful measurements of the masses and couplings of the dark particles involved can be obtained from a reasonably small sample of such events.
The dark matter WIMP proposed here has the following properties: (1) According to a rigorous theorem, its mass is $\le 125$ GeV. (2) According to approximate calculations of its annihilation cross-section, it will yield the observed dark matter abundance if its mass is $\sim$ 75 GeV. We also estimate that (3) the cross-section for nuclear scattering is consistent with the limits from direct detection experiments, (4) the cross-section for collider production is consistent with limits from the LHC, and (5) the cross-section for annihilation is consistent with the general (multiple-channel) limits from gamma-ray observations of dwarf spheroidal galaxies. The mass and annihilation cross-section (through 29 different channels) are in agreement with (6) analyses of the observations of gamma rays from the Galactic center by Fermi-LAT (supporting the hypothesis of WIMP annihilation) and (7) analyses of the antiprotons observed by AMS-02 (supporting this same hypothesis). (8) The most promising signature for collider detection appears to be missing transverse energy of $\sim$ 150 GeV following creation through vector boson fusion. (9) The best hope for direct detection is still Higgs exchange, although the coupling to the Higgs boson is undetermined. (10) According to another rigorous theorem, the present dark matter particle and the lightest neutralino of supersymmetry (susy) can stably coexist in a multicomponent dark matter scenario. This new dark matter candidate results from an extended Higgs sector which, if susy is included, implies a doubly rich plethora of new particles and new physics that should be observable in the foreseeable future.
Limitations on the most general mono-X Dark Matter signature at colliders motivate searches beyond this, such as multilepton plus missing energy signatures. In this talk I present our latest limits on the inert 2-Higgs Doublet model (I2HDM) and Minimal Fermion Dark Matter model (MFDM) for 8/13 TeV pp collisions at the LHC, producing 2-3 leptons plus missing energy final states, using CheckMATE. I will show how 3 lepton final states play an important role, with a leading role in the MFDM case via cascading Higgs decays. We also provide limits and efficiencies for re-interpretation of any scalar of fermion DM model by the community.
We consider an effective field theory framework with three standard model (SM) gauge singlet right handed neutrinos, and an additional SM gauge singlet scalar field. The framework successfully generates eV masses of the light neutrinos via seesaw mechanism, and accommodates a feebly interacting massive particle (FIMP) as dark matter candidate. Two of the gauge singlet neutrinos participate in neutrino mass generation, while the third gauge singlet neutrino is a FIMP dark matter. We explore the correlation between the ${\it vev}$ of the gauge singlet scalar field which translates as mass of the BSM Higgs, and the mass of dark matter, which arises due to relic density constraint. We furthermore explore the constraints from the light neutrino masses in this set-up. We chose the gauge singlet BSM Higgs in this framework in the TeV scale. We perform a detailed collider analysis to analyse the discovery prospect of the TeV scale BSM Higgs through its di-fatjet signature, at a future $pp$ collider which can operate with $\sqrt{s}=100$ TeV c.m.energy.
The Belle II experiment at the asymmetric $e^+e^-$ collider, SuperKEKB, is a substantial upgrade of the Belle/KEKB experiment. Belle II aims to record 50 ab$^{-1}$ of data over the course of the project. During the first physics runs in 2018-2020, around 100 fb$^{-1}$ of data were collected. These early data include specifically-designed low-multiplicity triggers which allow a variety of searches for light dark matter and dark-sector mediators in the GeV mass range. This talk will present the very first world-leading physics results from Belle II: searches for the invisible decays of a new vector Z’, and visible decays of an axion-like particle; as well as the near-term prospects for other dark-sector searches. Many of these searches are competitive with the data already collected or the data expected in the next few years of operation.
We study the prospects for probing models of inelastic dark matter (iDM) at the Fermilab-based Short Baseline Neutrino (SBN) experiments. In iDM models, elastic scattering of dark matter is suppressed, but the dark matter has an inelastic interaction with a slightly heavier excited dark sector state. The high-intensity Booster and NuMI proton beams can produce dark sector states in the MeV to GeV mass range that can then be detected at the SBN experiments. If the splitting between the two dark matter states is small, then excited dark sector states can propagate into the detectors and decay there. We demonstrate that the SBN experiments can probe new parts of iDM parameter space. Our study notably includes a simulation of iDM production and decay in the detectors, with a comparison to simulated backgrounds from neutrino scattering.
Accelerator-based searches for dark matter provide a unique opportunity to expand the search for particle dark matter to the sub-GeV mass regime.
In this region, there are exiting opportunities to search for dark sector signatures, mediators and the dark matter itself, that are unconstrained.
DarkQuest is a proton fixed-target experiment that would use a high-intensity beam of 120 GeV protons to produce dark sector mediators.
These mediators will interact feebly with the SM and decay into visible states with displaced lepton, photon and hadron decay signals.
DarkQuest will exploit the short baseline and compact spectrometer of the current beam dump experiment at Fermilab, SpinQuest, to search for these decays.
Because it builds on existing accelerator and detector infrastructure, it offers a powerful yet low-cost experimental initiative that can be realized on a short timescale.
In this talk we will discuss the current detector design, proposed upgrades and recent studies on the signal topology and the detector acceptance.
The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus on a narrower range of masses: the natural scenario where dark matter originates from thermal contact with familiar matter in the early Universe requires the DM mass to lie within about an MeV to 100 TeV. Considerable experimental attention has been given to exploring Weakly Interacting Massive Particles in the upper end of this range (few GeV – ~TeV), while the region ~MeV to ~GeV is largely unexplored. Most of the stable constituents of known matter have masses in this lower range, tantalizing hints for physics beyond the Standard Model have been found here, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well. It is therefore a priority to explore. If there is an interaction between light DM and ordinary matter, as there must be in the case of a thermal origin, then there necessarily is a production mechanism in accelerator-based experiments. The most sensitive way, (if the interaction is not electron-phobic) to search for this production is to use a primary electron beam to produce DM in ﬁxed-target collisions. The Light Dark Matter eXperiment (LDMX) is a planned electron-beam fixed-target missing-momentum experiment that has unique sensitivity to light DM in the sub-GeV range. This contribution will give an overview of the theoretical motivation, the main experimental challenges and how they are addressed, as well as projected sensitivities in comparison to other experiments.
New light particles may be produced in large numbers in the far-forward region at the LHC and then decay to dark matter, which can be detected through its scattering in far-forward experiments. In the talk, we will discuss the discovery potential of such far-forward searches for light dark matter scattering off electrons or nuclei in an emulsion or liquid argon detector placed on the beam collision axis during HL-LHC. For illustration, we will focus on a popular example of invisibly-decaying dark photons, which decay to dark matter through $A' \to \chi \chi$, while further prospects for probing BSM interactions of neutrinos will also be presented. These results motivate the construction of far-forward emulsion and liquid argon (FLArE) detectors, as well as a suitable location to accommodate them, such as the proposed Forward Physics Facility.
We present exoplanets as new targets to discover Dark Matter (DM). Throughout the Milky Way, DM can scatter, become captured, deposit annihilation energy, and increase the heat flow within exoplanets. We estimate upcoming infrared telescope sensitivity to this scenario, finding actionable discovery or exclusion searches. Supporting evidence of a DM origin can be identified through DM-induced exoplanet heating correlated with Galactic position, and hence DM density. This provides new motivation to measure the temperature of the billions of brown dwarfs, rogue planets, and gas giants peppered throughout our Galaxy.
The Gaia satellite will observe the positions and velocities of over a billion Milky Way stars. In the early data releases, the majority of observed stars do not have complete 6D phase-space information. We demonstrate the ability to infer the missing line-of-sight velocities until more spectroscopic observations become available. We utilize a novel neural network architecture that, after being trained on a subset of data with complete phase-space information, takes in a star’s 5D astrometry (angular coordinates, proper motions, and parallax) and outputs a predicted line-of-sight velocity with an associated uncertainty. Working with a mock Gaia catalog, we show that the network can successfully recover the distributions and correlations of each velocity component for stars that fall within ∼ 5 kpc of the Sun. We also demonstrate that the network can accurately reconstruct the velocity distribution of a kinematic substructure in the stellar halo that is spatially uniform, even when it comprises a small fraction of the total star count. Follow-up work includes applying the network to the Gaia catalogue and searching for kinematic substructure, which can provide useful information about the underlying dark matter distribution in the Milky Way.
After decays of overcoming numerous challenging obstacles, first principles lattice methods recently reported a calculation by our RBC-UKQCD Collaboration [see R. Abbott et al, Phys.Rev. D102 (2020) no.5, 054509] of K to pi pi amplitudes and direct CP parameter epsilon’; also shedding light into the long-standing issue of the delta I=1/2 Rule. Wrt the experimental observation of direct CP in D0 decays, it is suggested that the neighboring resonances cause enhancements resulting in consistency of the experimental results with expectations from the SM. Lastly, while recent experimental progress in direct CP in B+ to K+ pi0 is an important step forward, it does not necessarily signify any anomalous behavior so long as reliable quantitative estimates canot be made of non-factorizable effects as well as of isospin violations given that isospin is not a symmetry of electroweak interactions.
The lepton universality violating flavor ratios $R_K/R_{K^*}$ indicate new physics either in $b \to s \mu^+ \mu^-$ or in $b \to s e^+ e^-$ or in both. If the new physics is only $b \to s e^+ e^-$ transition, the corresponding new physics operators, in principle, can have any Lorentz structure. In this work, we perform a model independent analysis of new physics only in $b \to se^+e^-$ decay by considering effective operators either one at a time or two similar operators at a time. We include all the measurements in $b\rightarrow se^+e^-$ sector along with $R_K/R_{K^*}$ in our analysis. We show that various new physics scenarios with vector/axial-vector operators can account for $R_K/R_{K^*}$ data but those with scalar/pseudoscalar operators and with tensor operators can not. We also show that the azimuthal angular observable $P_1$ in $B \to K^* e^+ e^-$ decay is most suited to discriminate between the different allowed solutions.
The NA62 experiment at CERN reports the branching ratio measurement BR(K+→π+νν) at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare K+→π+νν decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839±0.054)×10−11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4±1.0)×10−11. The result represents the most accurate measurement achieved so far of this ultra-rare decay. Future prospects and plans for data taking from 2021 will also be presented.
Lepton flavor universality in vector interactions is a robust prediction of the Standard Model, and deviations from universality would necessitate new physics. The recent hints of lepton flavor non-universality in $B$ meson decays highlight the importance of complementary probes of lepton flavor universality, including in decays of $\Upsilon$ mesons. We report on a recent precision measurement of the ratio of branching fractions BF($\Upsilon(3S) \rightarrow \tau^+ \tau^-$) / BF($\Upsilon(3S) \rightarrow \mu^+ \mu^-$) using a sample of 122 million $\Upsilon(3S)$ mesons collected with the BaBar detector. The uncertainties in this measurement improve on earlier studies by almost an order of magnitude, and are of comparable order to the deviations predicted in certain models of lepton non-universality in $B$ meson decays.
Charmless $B$ decays provide a unique portion of the Belle II program. The expected large signal yields with moderate backgrounds associated with efficient reconstruction of neutral particles enable world-leading determination of the CKM phase $\alpha/\phi_2$, a conclusive understanding of the so-called K-$\pi$ CP puzzle, and further insight into the nature of localized CP violation in three-body decays. We report preliminary measurements based on the sample collected during 2019-2020 operations and corresponding to 65 fb$^{-1}$ of integrated luminosity. Results include a test of the $K\pi$ isospin sum-rule, an angular analysis of $B \to \rho^+ \rho^0$ decays, and the reconstruction of a $B^0 \to \pi^0\pi^0$ signal.
The Belle II experiment is a substantial upgrade of the Belle detector and will operate
at the SuperKEKB energy-asymmetric e+e− collider. The design luminosity of the machine
is 8 × 1035 cm−2s−1 and the Belle II experiment aims to record 50 ab−1 of data, a factor
of 50 more than its predecessor. From February to July 2018, the machine has completed a
commissioning run and main operation of SuperKEKB has started in March 2019. Belle II has
a broad τ physics program, in particular in searches for lepton flavour and lepton number
violations (LFV and LNV), benefiting from the large cross section of the pair wise τ
lepton production in e+e− collisions. We expect that after 5 years of data taking, Belle II
will be able to reduce the upper limits on LF and LN violating τ decays by an order of
magnitude. Any experimental observation of LFV or LNV in τ decays constitutes an unambiguous
sign of physics beyond the Standard Model, offering the opportunity to probe the underlying
New Physics. In this talk we will review the τ lepton physics program of Belle II.
Rare b-hadron decays are sensitive probes of New Physics through the study of branching fractions, angular observables, CP asymmetries.The LHCb experiment is ideally suited for the analysis of these decays due to its high trigger efficiency, as well as excellent tracking and particle identification performance. Recent results from the LHCb experiment are presented and their interpretation is discussed.
https://pitt.zoom.us/j/93687648384
We present a novel implementation of classification using boosted decision trees (BDT) on field programmable gate arrays (FPGA). The firmware implementation of binary classification requiring 100 training trees with a maximum depth of 4 using four input variables gives a latency value of about 10ns. Two problems are presented, in the separation of electrons vs. photons and in the selection of vector boson fusion-produced Higgs bosons vs. the rejection of the multijet processes. Implementations such as these enable the level-1 trigger systems to be more sensitive to new physics at high energy experiments. The work is described in [2104.03408].
An incipient program in Cosmic Ray and Radiation Detection is based at the International Elementary Particle Laboratory. Such efforts include an integral program to seek young talents, motivate them to pursue a STEAM oriented career and professionally train them in novel detection techniques by means of a hands-on approach that involves building innovative prototypes.
During the pandemic, over 30 prototypes meant to be used for radiation detection with novel materials, including metals, ionic liquids, and such, were planned, designed, and built remotely. They are now being tested, assembled, and placed on operation jointly with students who participate in the program. These novel detectors seek to detect cosmic rays and other forms of radiation with efficient, compact, and safe detectors.
In the Outreach phase, a series of online seminars were established to reach young talented kids with the aim to interest them in STEAM-oriented Careers. Those seminars have reached to date, over 530,000 people from all over Latin America primarily in the ages of 13-24 years old. Speaker include Julián Félix, Juan Maldacena, Juan Estrada, Gastón Gutiérrez, Fernando Quevedo, Gabriela González, Matias Zaldarriaga, Alberto Rojo and José Manuel Sánchez Ron amongst others.
A framework is presented to extract and understand decision-making information from a deep neural network classifier of jet substructure tagging techniques. The general method studied is to provide expert variables that augment inputs (“eXpert AUGmented” variables, or XAUG variables), then apply layerwise relevance propagation (LRP) to networks that have been provided XAUG variables and those that have not. The XAUG variables are concatenated to the classifier’s intermediate input to the final layer.The results show that XAUG variables can be used to interpret classifier behavior, increase discrimination ability when combined with low-level features, and in some cases capture the behavior of the classifier completely. The LRP technique can be used to find relevant information the network is using, and when combined with the XAUG variables, can be used to rank features, allowing one to find a reduced set of features that capture a majority of network performance. These identified XAUG variables can also be added to low-level networks as a guide to improve performance.
*This work was supported under NSF Grants PHY-1806573, PHY-1719690 and PHY-1652066. Computations were performed at the Center for Computational Research at the University at Buffalo.
Jet identification tools are crucial for new physics searches at the LHC and at future colliders. We introduce the concept of Mass Unspecific Supervised Tagging (MUST) which relies on considering both jet mass and transverse momentum varying over wide ranges as input variables - together with jet substructure observables - of a multivariate tool. This approach not only provides a single efficient tagger for arbitrary ranges of jet mass and transverse momentum, but also an optimal solution for the mass correlation problem inherent to current taggers. By training neural networks, we build MUST-inspired generic and multi-pronged jet taggers which, when tested with various new physics signals, clearly outperform the variables commonly used by experiments to discriminate signal from background. These taggers are also efficient to spot signals for which they have not been trained. Taggers can also be built to determine, with a high degree of confidence, the prongness of a jet, which would be of utmost importance in case a new physics signal is discovered.
A new software tool MInOS (Machine Intelligent Optimization of Significance) is introduced for the automation of machine learning on collider event statistics, with back-end functionality provided by the XGBoost package. A simple, compact, and powerful meta-language syntax facilitates the generation of sophisticated Boosted Decision Tree analyses based upon instructions supplied in a reusable card file. MInOS integrates transparently with MadGraph/Pythia/Delphes and handles the weighted recombination and over-sampling of simulated data. All event statistics computable by the companion package AEACuS (and arbitrary user-supplied functions thereof) may be leveraged as learning keys, or as criteria for manual event selection. Ensemble training against distinct background components may be combined to generate composite classifications with enhanced discrimination, and trained models may be stored or converted into standalone executable code for reapplication. ROC curves as well as score distribution, feature importance, and significance threshold plots are generated on the fly.
The high-intensity setup and detector performance make the NA62 experiment at CERN particularly suited for searching new physics effects from different scenarios involving feebly interacting particles in the MeVGeV mass range.
A search for the K+→π+X decay, where X is a long-lived feebly interacting particle, is performed through an interpretation of the K+→π+νν¯ analysis of data collected in 2017-2018. Model- dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs. Upper limits set on the branching ratio BR(K+→π+X) improve on current limits for mX below 260 MeV/c2 and rest lifetimes above 100 ps.
A search for K+→μ+νX, where X is a massive invisible particle, is performed using the 2016-2018 data set. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state. Upper limits of the decay branching fraction for X masses in the range 10-370 MeV/c2 are reported for the first time, ranging from O(10−5) to O(10−7).
A study of a sample of 4×10ˆ9 tagged π0 mesons from K+→π+π0(γ) is performed, searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4×10−9 is set on the branching ratio at 90% C.L. improving on previous results by a factor of 60.
While the QCD axion is often considered to be necessarily light (eV), recent work has opened a viable and interesting parameter space for heavy axions, which solve both the Strong CP and the axion Quality Problems. These well-motivated heavy axions, as well as the generic axion-like-particles, call for explorations in the GeV mass realm at collider and beam dump environments. The primary upcoming neutrino experiment, Deep Underground Neutrino Experiment (DUNE), is simultaneously also a powerful beam dump experiment, enabled by its multipurpose Near Detector (ND) complex. In this study, we show with detailed analyses that the DUNE ND has a unique sensitivity to heavy axions for masses between 20 MeV and 2 GeV, complementary to other future experiments.
Axion-like particles (ALPs) provide a promising direction in the search for new physics, while a wide range of models incorporate ALPs. We point out that neutrino and dark matter experiments, such as DUNE and CCM, possess competitive sensitivity to ALP signals. High-intensity proton beams can not only produce copious amounts of neutrinos, but also cascade photons that are created from charged particle showers stopping in the target. Therefore, ALPs interacting with photons can be produced (often energetically) with high intensity via the Primakoff effect $\gamma Z \rightarrow a Z$ and then leave their signatures via inverse Primakoff scattering or decays to photon pairs, $a \rightarrow \gamma \gamma$. The proton beam may also induce an electron flux, which, together with the cascade photons, can produce ALPs via their couplings to electrons through bremsstrahlung-like and compton-like processes. Through this coupling, ALP detection via decays to $e^+ e^-$ and inverse compton scattering $a e^- \rightarrow \gamma e^-$ are also possible.
.
The discrepancy between the muon g−2 measurement and the Standard Model prediction points to new physics around or below the weak scale. It is tantalizing to consider the loop effects of a heavy axion (in the general sense, also known as an axion-like particle) coupling to leptons and photons as an explanation for this discrepancy. We provide an updated analysis of the necessary couplings, including two-loop contributions, and find that the new physics operators point to an axion decay constant on the order of 10s of GeV. This poses major problems for such an explanation, as the axion couplings to leptons and photons must be generated at low scales. We outline some possibilities for how such couplings can arise, and find that these scenarios predict new charged matter at or below the weak scale and new scalars can mix with the Higgs boson, raising numerous phenomenological challenges. These scenarios also all predict additional contributions to the muon g−2 itself, calling the initial application of the axion effective theory into question. We conclude that there is little reason to favor an axion explanation of the muon g−2 measurement relative to other models postulating new weak-scale matter.
I will talk about a ``heavy'' QCD axion whose coupling to the standard model is dominated by $a G \widetilde{G}$ but with $m_a \gg m_\pi f_\pi / f_a$. This is well motivated as it can solve the strong CP problem while evading the axion quality problem. Such axion with mass around a GeV is kinematically inaccessible or poorly constrained by most experimental probes except B-factories. We study $B \to K a$ transitions as a powerful probe of the heavy QCD axion by performing necessary 2-loop calculations for the first time, together with some improvement on the existing analysis strategy. We find some of the existing limits are enhanced by at least an order of magnitude. For forthcoming data sets of the Belle II experiment, we provide a projection that $f_a$ of a few TeV is within its future reach, which is relevant to the quality problem.
Axion-like particles (ALPs) are pseudo-Nambu-Goldstone bosons of spontaneously broken global symmetries in theories attempting to address the incompleteness of the Standard Model (SM). In particular, ALPs arise in theoretical resolutions to the strong CP problem, offer explanations for the dark matter (DM) relic abundance, and are ubiquitous in string theory. The ALP mass $m_a$ can range from eV to TeV scale, and thus the ALPs parameter space includes regions relevant to a variety of astronomical, high-precision low-energy, and high-energy collider experiments. The focus of this talk is a feasibility study searching for ALPs using vector boson fusion (VBF) processes at the Large Hadron Collider (LHC). We consider the $a \to \gamma\gamma$ decay mode to show that the requirement of an energetic diphoton pair combined with two forward jets with large dijet mass and pseudorapidity separation can significantly reduce the SM backgrounds, leading to a 5$\sigma$ discovery region spanning $m_a$ values from MeV scale to TeV scale and revealing LHC sensitivity to previously unstudied regions of the ALP parameter space.
While supernovae and cooling neutron stars have long been fruitful environments for constraining dark sector particles such as axions, neutron star mergers offer a novel territory to explore BSM physics and look for its signatures in the electromagnetic and gravitational wave signals from the merger. Axions interact weakly with hot, dense nuclear matter and therefore will escape from the merger remnant, cooling it. We find that significant cooling can occur on the timescales relevent for neutron star mergers. Other BSM particles, within current constraints on their parameters, may be trapped inside the merger remnant, perhaps contributing significantly to thermal equilibration of the nuclear matter in the remnant. We calculate the timescale of thermal equilibration due to a trapped gas of CP-even scalar particles inside a merger remnant.
Top quark production in association with additional particles at CMS: tt+bb, tt+cc, ttZ, ttW, ttgamma, tZ and tttt production
Third-generation leptoquarks are considered the most viable particles that explain anomalous ratios of decays to different lepton flavors seen in B decays. In this talk, we present several recent results, including a new search for leptoquark pair production, as well as single-leptoquark and t-channel production for leptoquarks that couple strongly to third-generation particles.
We present the search for heavy resonances decaying to a pair of bosons, WZ or ZZ, where one Z decays to a pair of neutrinos, and the other W or Z boson decays to a merged jet due to the boost. At the LHC these resonances can be produced through quark/anti-quark annihilation, gluon-gluon fusion, or weak vector boson fusion (VBF) processes. Tagging techniques for both forward jets produced in the VBF process and for identifying quarks from W/Z decays which fragment into a merged jet will be discussed. Challenges to traditional semi-visible resonance search techniques, which arise from a confluence of polarization effects and a partially reconstructed final state, will be presented. Finally, recent results in the context of scenarios beyond the standard model using LHC Run-2 datasets with the CMS detector will be given.
We present a summary of searches for new heavy resonances decaying into pairs or triplets of bosons, performed on proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV. A common feature of these analyses is the boosted topology, namely the decay products of the considered bosons (both electroweak W, Z bosons and the Higgs boson) are expected to be highly energetic and close in angle, leading to a non-trivial identification of the quarks and leptons in the final state. The exploitation of jet substructure techniques allows to increase the sensitivity of the searches where at least one boson decays hadronically. Various background estimation techniques are adopted, based on data-MC hybrid approaches or relying only in control regions in data. Results are interpreted in the context of multiple scenarios beyond the standard model.
We discuss new bounds on vectors coupled to currents whose non-conservation is due to mass terms, such as $U(1)_{L_\mu - L_\tau}$. In scenarios with Stueckelberg masses for such gauge bosons, due to the emission of many final state longitudinally polarized gauge bosons, inclusive rates grow exponentially fast in energy, leading to strong constraints. We present bounds coming from the high invariant mass tail of di-lepton events at the LHC, which beat out cosmological bounds to place the strongest limit on Stueckelberg $U(1)_{L_\mu - L_\tau}$ models for most masses below a keV. We also discuss a stronger, but much more uncertain, bound coming from the validity of perturbation theory at the LHC.
Though collider searches are constraining supersymmetric parameter space, generic model independent bounds on sneutrinos remain very low. We calculate new model independent lower bounds on general supersymmetric scenarios with sneutrino LSP and NLSPs. By recasting ATLAS LHC exotic searches in mono boson channels, we place an upper bound on the cross section on $pp\rightarrow\tilde{\nu}\tilde{\nu}+V$ processes in mono-photon, mono-$Z$ and mono-Higgs channels. We also evaluate the LHC discovery potential of sneutrinos in the HL-LHC 3 $ab^{-1}$ run.
We present a study of the production of a single top quark in association with a
heavy extra Z′ at hadron colliders in new physics models with and without flavor-changing neutral-current (FCNC) couplings. We use QCD soft-gluon resummation and threshold expansions to calculate higher-order corrections for the total cross section and transverse-momentum distributions for tZ′ production. The impact of uncertainties due to the structure of the proton and scale dependence is also discussed.
We present an overview of searches for new physics with top and bottom quarks in the final state, using proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV. The results cover non-SUSY based extensions of the SM, including heavy gauge bosons or excited third generation quarks. Decay channels to vector-like top partner quarks are also considered. We explore the use of jet substructure techniques to reconstruct highly boosted objects in events, enhancing the sensitivity of these searches.
Many extensions to the Standard Model predicts new particles decaying into two bosons (W, Z, photon, or Higgs bosons) making these important signatures in the search for new physics. Searches for such diboson resonances have been performed in final states with different numbers of leptons, photons, as well as jets and b-jets where new jet substructure techniques are used to disentangle the hadronic decay products in highly boosted configuration. This talk summarises recent ATLAS searches with Run 2 data collected at the LHC.
Searches for new physics in events with jets in the final state in CMS
The recent results from the LHC suggest that the next search for New Physics should be performed in the low-energy mass range using high-intensity beams. That has revived the interest in the phenomenology of new light particles with feeble interactions with the Standard Model[1]. The DOE in the US is perfectly positioned for that quest with four laboratories (FNAL, ORNL, BNL, and LANL) capable of providing intense proton beams in the 1 - 10 GeV energy range. Light dark matter must be neutral under SM charges, otherwise it would have been discovered at previous colliders[2]. The only known particles with all-zero quantum numbers are the $\eta$/$\eta$' mesons and the Higgs boson. They provide an excellent laboratory to search for New Physics. An $\eta$ factory is within the reach of each of the four aforementioned laboratories.
The REDTOP experiment is being designed to produce $10^{13}$ $\eta$ mesons and $10^{11}$ $\eta$' mesons. Two different production mechanisms are available, depending on the energy and intensity of the beam. The physics sectors which can be probed at REDTOP range from the violation of discrete symmetries to the search for new particles. Non-eta meson sectors can also be explored, such as ALPS and QCD-axions. Finally, the Standard Model can be probed at low energy at an unprecedented level. Novel detector techniques needs to be developed to cope with the high interaction rate. Future High Energy and High Intensity experiments will benefit from that R&D. A collaboration has been forming since several years with the intent of submitting a proposal to the US HEP Community.
[1] J. Alexander et al., Dark Sectors 2016 Workshop: Community Report, 2016, http://inspirehep.net/record/1484628/files/arXiv:1608.08632.pdf
[2] https://indico.fnal.gov/event/44819/contributions/193751/attachments/132857/163535/RF6-Kickoff-DM-Production.pdf
The FASER experiment is a new small and inexpensive experiment that is being placed 480 meters downstream of the ATLAS experiment at the CERN LHC. The experiment will shed light on currently unexplored phenomena, having the potential to make a revolutionary discovery. FASER is designed to capture decays of exotic particles, produced in the very forward region, out of the ATLAS detector acceptance. This talk will present the physics prospects, the detector design, and the construction progress of FASER. The experiment has been successfully installed and will take data during the LHC Run-3.
A modest extension of the Standard Model by two additional Higgs doublets - the Higgs Troika Model - can provide a well-motivated scenario for successful baryogenesis if neutrinos are Dirac fermions. Adapting the "Spontaneous Flavor Violation" framework, we consider a version of the Troika model where light quarks have significant couplings to the new multi-TeV Higgs states. Resonant production of new scalars leading to di-jet or top-pair signals are typical predictions of this setup. The initial and final state quarks relevant to the collider phenomenology also play a key role in baryogenesis, potentially providing direct access to the relevant early Universe physics in high energy experiments. Viable baryogenesis generally prefers some hierarchy of masses between the observed and the postulated Higgs states. We show that there is a complementarity between direct searches at a future 100 TeV $pp$ collider and indirect searches at flavor experiments, with both sensitive to different regions of parameter space relevant for baryogenesis. In particular, measurements of $D-\bar{D}$ mixing at LHCb probe much of the interesting parameter space. Direct and indirect searches can uncover the new Higgs states up to masses of $\mathcal{O}(10)$ TeV, thereby providing an impressive reach to investigate this model.
Electroweak symmetry non-restoration up to high temperatures well above the electroweak scale has intriguing implications for (electroweak) baryogenesis and early universe thermal histories. In this talk, I will discuss a new approach for electroweak symmetry non-restoration via an inert Higgs sector that couples to the Standard Model Higgs as well as an extended scalar singlet sector. Examples of benchmark scenarios that allow for electroweak symmetry non-restoration all the way up to hundreds of TeV temperatures, featuring suppressed sphaleron washout factors down to the electroweak scale, will be presented. Renormalization group improvements and thermal resummation, necessary to evaluate the effective potential spanning over a broad range of energy scales and temperatures, have been implemented calculating the thermal history. This method for transmitting the Standard Model broken electroweak symmetry to an inert Higgs sector can be scrutinized through Higgs physics phenomenology and electroweak precision measurements at the HL-LHC.
Novelty detection is a task of Machine Learning to detect novel events without a prior knowledge. Its techniques can be applied to detect unexpected signals of new physics at colliders. We generalize the complementary strategies developed in the paper (arxiv:1807.10261) for achieving this task. Generally, the novelty evaluators are classified into two categories: isolation-based and clustering (density)-based. Properly combining the evaluators from each category yields a third category, namely "synergy-based", which may significantly improve the efficiency and quality of novelty evaluation. We demonstrate these features by analyzing the performances of the three category of evaluators, using a variety of two dimensional Gaussian samples mimicking collider events. This study is subsequently applied to the LHC detection of the $t\bar th$ Higgs physics and the gravity-mediated supersymmetry as novel events in the $t\bar t\gamma\gamma$ channel. These two scenarios represent the signal patterns with a sharp resonance and a broad distribution of $m_{\gamma\gamma}$, respectively. The sensitivities at detector level are provided, which read encouraging compared to the ongoing LHC analysis.
The simplified limits framework is an approach developed to recast limits on searches for narrow resonances in terms of products of branching ratios (BRs) corresponding to the resonance's production and decay modes. In this talk, we will present an extension of the framework to a multidimensional parameter space of BRs. This can be used in a model-independent way to unfold an ambiguity in the simplified parameter $\zeta$ introduced when more than one channel contributes to the production of the resonance, and is naturally applicable to combining constraints from experimental searches with multiple observed final states. These constraints are visualized in a three-dimensional space of branching ratios by employing ternary diagrams, triangle plots which utilize the inherent unitarity of the sum of the resonance's BRs. We will briefly discuss the broader application of N-simplexes to parameterize and store digital data sets.
I will discuss the correlation between dark matter and Higgs decays in gauge theories where the dark matter is predicted from anomaly cancellation. In these theories, the Higgs responsible for the breaking of the gauge symmetry generates the mass for the dark matter candidate. We investigate the Higgs decays in the minimal gauge theory for Baryon number. After imposing the dark matter density and direct detection constraints, we find that the new Higgs can have a large branching ratio into two photons or into dark matter. Furthermore, we discuss the production channels and the signatures at the Large Hadron Collider
Two Higgs Doublet Model (2HDM) offers a prototype beyond the Standard Model (SM) with an extended Higgs sector. It provides a rich spectrum of scalars, of which some can be relatively light with weak couplings to the SM particles. Complementary to the usual searches for extra scalars at high energy colliders, FASER offers a unique opportunity to study those relatively long-lived light scalars. Given all the existing theoretical and experimental constraints, we consider the light CP-even and CP-odd scalars in the four different types of 2HDMs, and examine the parameter window which can be probed at FASER.
Results on rare and new top quarks interactions, including EFT, in CMS
https://pitt.zoom.us/j/96734791723
Cosmology experiments are often based on large-scale surveys on satellite and need methods to perform in-flight relative flux self-calibrations of their spectro-photometer instruments. In this talk a method is proposed where the instrument response function is inferred with a chi square statistics in an unbiased way, simulating a simplified sequence of observations with realistic distributions of sources and count rates. A validation of the method, with the definition of figures of merit to quantify the expected performances, will also be presented.
There are currently tensions between observations of the early and late Universe in the determination of the cosmological parameters $S_8$ and $H_0$. In this talk, I will discuss a new phenomenological model that addresses these tensions. Our scenario features: (i) a decaying dark energy fluid, which undergoes a transition at $z \sim 5,000$, to raise today's value of the Hubble parameter -- addressing the $H_0$ tension, and (ii) an ultra-light axion, which starts oscillating at $z\sim 16,000$, to suppress the matter power spectrum -- addressing the $S_8$ tension. Our Markov Chain Monte Carlo analyses show that such a Dark Sector model fits a combination of early time datasets slightly better than the $\Lambda$CDM model, while reducing both the $H_0$ and $S_8$ tensions to $ <\sim3\sigma$ level. Combined with measurements from cosmic shear surveys, we find that the discrepancy on $S_8$ is reduced to the $1.4\sigma$ level, and the value of $H_0$ is further raised. Adding local supernovae measurements, we find that the $H_0$ and $S_8$ tensions are reduced to the $1.5\sigma$ and $1.1\sigma$ level respectively, with a significant improvement $\Delta\chi^2\simeq -17$ compared to the $\Lambda$CDM model. A particle physics realization of this model could be found in a dark confining gauge sector and its associated axion, although embedding the full details within microphysics remains an urgent open question. This scenario will be decisively probed with future CMB surveys. This talk is based on Ref. 2104.12798.
Based on: JCAP 03 (2021) 084 (arXiv: 2012.07519)
We have updated the constraints on flavor universal neutrino self-interactions mediated by a heavy scalar, in the effective 4-fermion interaction limit. Based on the latest CMB temperature data from the Planck 2018 data release as well as auxiliary data we confirm the presence of a region in parameter space with relatively strong self-interactions which provides a better than naively expected fit. However, we also find that the most recent data, in particular high-ℓ polarisation data from the Planck 2018 release, disfavors this solution even though it cannot yet be excluded. Our analysis takes into account finite neutrino masses (parameterized in terms of $\sum m_{\nu}$) and allows for a varying neutrino energy density (parameterized in terms of $N_{\rm eff}$), and we find that in all cases the neutrino mass bound inferred from cosmological data is robust against the presence of neutrino self-interactions. Finally, we also find that the strong neutrino self-interactions do not lead to a high value of $H_0$ of around 73 km/s/Mpc being preferred as long as CMB high-ℓ polarisation data from the Planck 2018 is included, i.e. this model does not seem like a viable solution to the current $H_0$ discrepancy.
The standard Lambda CDM cosmological model now seems to face some puzzles. One of the most serious problems is the so-called Hubble tension; the values of the Hubble constant obtained by local measurements look inconsistent with that inferred from CMB. Although introducing extra radiations $\Delta N_{\textrm{eff}}$ such as hot axions or sterile neutrinos appears to be promising, such extra radiations increase the Helium mass fraction synthesized by Big Bang Nucleosynthesis (BBN). To cancel such an increment, positive electron neutrino asymmetry $\xi_{e}$ may be also needed. By analysing the data from Planck, baryon acoustic oscillation (BAO), BBN and type-Ia supernovae, we evaluate the possibility of the non-zero lepton asymmetry and extra radiations.
A previous analysis of light curves from 13 quasars in the MACHO survey has shown some cor-relation among short time scale variations. Particularly, in the quasar’s rest frame, linear segments over time scales on the order of 100 days indicate a common slope. Though the source of this feature is at present unknown, such a commonality could allow one to determine the relative redshift of one quasar to another by comparing light curves thereby adding another benchmark to the cosmic distance ladder. We here extend the previous analysis to the remaining 46 well-sampled quasars in the MACHO survey and an additional∼9200 under-sampled quasars from the Sloan Digital Sky Survey. The feature proves to be persistent among the majority of quasars but requires the sampling rate of the quasar to be on average once every 15 days to reliably estimate the redshift.
In string theory picture, Planck scale $M_{\rm Pl}$, the supersymmetry-breaking scale $m_s$, electroweak scale $m_{\rm EW}$ and vacuum energy density (cosmological constant) $\Lambda$ are to be dynamically determined from string scale $M_S$. Here we consider a model that links the supersymmetric electroweak phenomenology to string theory motivated flux compactification approach. The model breaks supersymmetry through a combination of the racetrack K\"ahler uplift mechanism and anti-D3-brane in the KKLT. The introduction of the Higgs field allows a small $\Lambda$ and a big $m_s$ simultaneously.
Non-local quantum field theories have been studied recently as a promising approach to go beyond the Standard Model (e.g. see [1–3]). This approach is strongly motivated by string theory (p-adic string field theory) [4–6]. These theories have the properties of UV-completeness and (proposed as a direction of UV-completion the non-local inifinte-derivative theories) are ghost-free (re-normalizable and predicts conformal invariance at the quantum level) [7]. They are able to rescue dark matter models [3], move trans-planckian processes to sub-planckian [8] and improve inflationary behaviour of the Higgs field [9]. On the same research avenues, we consider an infinite derivative scalar field theory and we show, by a technique devised by Bender, Savage and Milton [10], how to derive the set of Dyson-Schwinger equations in differential form. Then, we provide a method to solve them, assuming that non-local effects are small at low-energies and taking into account only the leading order solutions [11]. Local solutions for the scalar field theory, both for the classical and the quantum case have been recently obtained [12–15] and can be applied also to the solution of the Yang-Mills theory [16] and confinement studies can be accomplished with Kugo-Ojima crtierion properly generalized [17]. It is seen that UV-limit is never reached in this cse. In these studies, we just assume that they represent the local solutions to start from to get the corrections due to the non-locality. An immediate consequence of this approach is that the a mass gap is obtained and the spectrum of the theory becomes computable. In any case, the mass gap is diluted and these theories become conformal in the UV-limit. By analogy, also the graviton propagator possibly would get a mass gap that is diluted in the UV-limit reaching a conformal limit.
The worldline effective field theory formalism provides a systematic approach to probe the post-Minkowskian binary scattering processes. Expanding to include spin degrees of freedom, we compute the total change in momentum and spin in the gravitational scattering of compact objects to next-to-leading PM order with linear and bilinear spin effects and arbitrary initial conditions. Using the Boundary-to-Bound correspondence we construct the radial action for elliptic-like orbits for the aligned spin configurations.
The $\Lambda$CDM model provides an excellent fit to the CMB data. However, a statistically significant tension emerges when its determination of the Hubble constant $H_0$ is compared to the local distance-redshift measurements. The axi-Higgs model, which couples ultralight axions to the Higgs field, offers a specific variation of the $\Lambda$CDM model. It relaxes the $H_0$ tension as well as explains the $^7$Li puzzle in Big-Bang nucleosynthesis, the $S_8$ tension with the weak-lensing data, and the observed isotropic cosmic birefringence in CMB. In this letter, we demonstrate how the $H_0$ and $S_8$ tensions can be resolved simultaneously, by correlating the axion impacts on the early and late universe. In a benchmark scenario selected for experimental tests soon, the analysis combining the CMB+BAO+WL+SN data yields $H_0 = 71.1 \pm 1.1$ km/s/Mpc and $S_8 = 0.766 \pm 0.011$. Combining this (excluding the SN(supernovae) part) with the local distance-redshift measurements yields $H_0 = 72.3 \pm 0.7$ km/s/Mpc, while $S_8$ is unchanged.
Dark matter could take the form of macroscopic objects, scattering on baryonic matter with geometric cross section. There is a wide "asteroid" mass range over which such objects are almost unconstrained. We show that when a dark asteroid travels through a star, it produces shock waves which reach the stellar surface, leading to a distinctive transient UV emission. In a dense globular cluster, such transients occur far more often than flare backgrounds, and an existing UV telescope could probe five orders of magnitude in dark matter mass in one day of observation.
Indirect detection experiments typically measure the flux of annihilating dark matter (DM) particles propagating freely through galactic halos. We consider a new scenario where celestial bodies "focus" DM annihilation events, increasing the efficiency of halo annihilation. In this setup, DM is first captured by celestial bodies, such as neutron stars or brown dwarfs, and then annihilates within them. If DM annihilates to sufficiently long-lived particles, they can escape and subsequently decay into detectable radiation. This produces a distinctive annihilation morphology, which scales as the product of the DM and celestial body densities, rather than as DM density squared. We show that this signal can dominate over the halo annihilation rate in γ-ray observations in both the Milky Way Galactic center and globular clusters. We use \textit{Fermi} and H.E.S.S. data to constrain the DM-nucleon scattering cross section, setting powerful new limits down to ∼10^{−39} cm2 for sub-GeV DM using brown dwarfs, which is up to nine orders of magnitude stronger than existing limits. We demonstrate that neutron stars can set limits for TeV-scale DM down to about 10^{−47} cm2
We examine a real electroweak triplet scalar field as dark matter, abandoning the requirement that its relic abundance is determined through freeze out in a standard cosmological history (a situation which we refer to as `miracle-less WIMP'). We extract the bounds on such a particle from collider searches, searches for direct scattering with terrestrial targets, and searches for the indirect products of annihilation. Each type of search provides complementary information, and each is most effective in a different region of parameter space. LHC searches tend to be highly dependent on the mass of the SU(2) charged partner state, and are effective for very large or very tiny mass splitting between it and the neutral dark matter component. Direct searches are very effective at bounding the Higgs portal coupling, but ineffective once it falls below $\lambda_{\text{eff}} \sim 10^{-3}$. Indirect searches suffer from large astrophysical uncertainties due to the backgrounds and $J$-factors, but do provide key information for $\sim$ 100 GeV to TeV masses. We determine the parameter space for this example of miracle-less WIMP dark matter that can be robustly excluded, and which parts of it remain viable.
Weak-scale secluded sector dark matter can reproduce the observed dark matter relic density via thermal freeze-out within that sector. If supersymmetric, three portals to the visible sector — a gauge portal, a Higgs portal, and a gaugino portal — are present. We present the gamma ray spectra relevant for indirect detection in these set-ups. Since R-parity is no longer necessary to ensure dark matter stability, we investigate the impact of R-parity violation on the annihilation spectra. We present limits from the Fermi Large Area Telescope (LAT) analysis of dwarf galaxies and projections for the Cherenkov Telescope Array (CTA) probe of the galactic center.
Numerous particle models for the cosmological dark matter feature a pair-annihilation rate that scales with powers of the relative velocity between the annihilating particles. As a result, the annihilation rate in the central regions of dark matter halo can be significantly lower than at the halo's periphery for particular ambient gravitational potentials. While this might be offset by an increasing dark matter pair number density in the inner halo, it raises the question: what angular region for dark matter models with velocity-suppressed annihilation rates optimizes signal-to-noise? Here, we consider simplified background models for galactic and extragalactic targets and demonstrate that the optimal observing strategy varies greatly case-by-case. Generally, a bright central source warrants an annular region of interest, while a flatter noise profile warrants as large as possible an angular region, possibly including the central regions.
The paradigm of neutral naturalness suggests the existence of highly non-minimal hidden sectors. In particular, the Mirror Twin Higgs model postulates that some of dark matter is in the form of mirror matter, featuring mirror quarks, leptons and gauge bosons whose masses are a few times heavier than their Standard Model counterparts. I will discuss the possibility that mirror matter could have coalesced into Mirror Neutron Stars, invisible cousins of ordinary neutron stars. I will show how the properties of Mirror Neutron Stars can be determined using repurposed Lattice QCD data, and discuss the gravitational wave signatures of Mirror Neutron Star mergers. Given the impressive reach of current and future gravitational wave detectors, gravitational wave astronomy may offer a novel and powerful means of detecting (or constraining) non-minimal dark sectors.
I report on an ongoing investigation of how a hidden ‘dark’ confining gauge sector, common in Hidden Valley models such as the Mirror Twin Higgs, could lead to novel signatures in indirect detection searches for dark matter. Dark matter annihilation can then lead to dark showers of multiple and various hadrons, distinct from particle pair production. If there are no light fermions charged under this force, the lightest hadrons are glueballs, a spectrum of a dozen metastable states that is reasonably well understood from lattice calculations. The lightest of these states, the $0^{++}$ glueball, can mix with the Higgs and decay through this portal into the Standard Model (SM). The decay of $0^{++}$ glueballs has been studied within the context of collider searches, as it is the shortest lived state, decaying on scales that can be observed as displaced vertices. However, since indirect detection methods probe astrophysical length and time scales, they are also sensitive to the decays of longer living glueball states that can decay into $0^{++}$ and SM particles; this leads to an increased multiplicity of particles such as positrons and antiprotons, but also possibly probes the properties of the entire glueball spectrum. Since the decays depend on the allowed operators, this may allow information on the UV completion of the sector to be determined. Understanding the possible indirect signatures and constraints of a pure glue gauge theory is especially relevant as the next generation of cosmic ray telescopes, such as GAPS, begin their searches.
Gravitational waves provide a unique method of testing theories with extended gauge symmetries. In particular, spontaneous symmetry breaking can lead to a detectable stochastic gravitational wave background generated by cosmic strings and first order phase transitions in the early universe. I will discuss the unique gravitational wave signature of a simple model with gauged baryon and lepton numbers, in which a high scale of lepton number breaking is motivated by the seesaw mechanism for the neutrinos, whereas a low scale of baryon number breaking is required by the observed dark matter relic density. This novel signature can be searched for in near-future gravitational wave experiments.
https://pitt.zoom.us/j/95618235024
Low energy probes of lepton flavor violation (LFV) are indirectly probing new physics beyond the TeV scale, with order of magnitude advances expected in the future. A high energy muon collider would have the reach to probe similar processes at higher energies, e.g., via 𝜇𝜇→𝜏𝜇, which can be compared to the low-energy flavor-violating decay bounds. Alternatively, in particular models of new physics, new particles with flavor-violating interactions can be produced directly, such as mixed slepton pair production in the MSSM. I’ll present some first estimates of the physics reach of a muon collider for both of these scenarios, with an emphasis on the complementarity between low-energy precision experiments and high-energy muon collider searches.
We identify the two scalar leptoquarks capable of generating sign-dependent contributions to leptonic magnetic moments, 𝑅2∼(3,2,7/6) and 𝑆1∼(3,1,−1/3), as is a strong possibility given current measurements. We consider the case in which the electron and muon sectors are decoupled, and real-valued Yukawa couplings are specified using an up-type quark mass-diagonal basis. This allows us to identify a previously overlooked region of parameter space, where strong constraints from LFV decays may be avoided. We also comment on the viability of these simple models for studies of leptonic EDMs. This analysis can be embedded within broader flavour anomaly studies, including those of hierarchical leptoquark coupling structures.
The M1 radiative transitions of heavy flavor baryons are studied in the framework of Effective Mass Scheme (EMS) within the quark model. The intent of the EMS lies in the fact that the masses of the quarks inside the baryon are modified as a consequence of one-gluon exchange interaction with the spectator quarks and it treats all the quarks at the same footing. The baryon mass can be written as the sum of the constituent quark masses and the spin-dependent hyperfine interaction
among them. We show that EMS can successfully describe the masses and the magnetic moments, transition moments, and radiative decay widths of the lowest-lying singly heavy flavor baryons in a parameter independent way. For the calculation of effective quark masses, the exchange contribution is worked out through interaction terms bij from the recently observed experimental masses for the heavy flavored charm and bottom baryons. We then compute the magnetic and transition moments of ground state J^P = (1/2)^(+) and J^P = (3/2)^(+), and(1/2)^('+) → (1/2)^(+), (3/2)^(+) → (1/2)^(+), and (3/2)^(+) → (1/2)^('+) heavy flavor charm and bottom baryon states. Finally, we make sturdy model independent predictions for radiative M1 decay widths of heavy flavored baryons. The radiative transitions between the states occur mainly through the M1-type, while there are negligible contributions from E2-type transitions, which are
therefore ignored. We also extend our analysis to the triply heavy charm and bottom baryons.
$\sin 2 \phi_1 ~(\sin 2 \beta)$ is measured using the $CP$-eigenstates induced by the $b \to c$ tree diagram and it is the most precise variable among the CKM angles.
We have presented the result of the measurement using the $B^0 \to J/\psi K^0_S$ decay collected from the early Belle II data. On the other hand, it can be measured also using the decays induced by $b \to s$ penguin diagram. In that case, contribution of the new physics is expected so that effective $\sin 2 \phi_1 \equiv \sin 2 \phi_1^{\rm eff}$ is measured. In relation to those measurements, we present the re-discoveries of the $B^0 \to J/\psi K^0_L$ and $B^0 \to \eta’ K^0_S$ decays using the data set obtained by the Belle II in 2019 and 2020. Former one is a good indicator to check the difference of $CP$ eigenvalue between $B^0 \to J/\psi K^0_S$. Latter one is one of the modes used for $\sin 2 \phi_1^{\rm eff}$ measurement and its branching fraction is relatively large.
Run 2 of the LHC has witnessed the observation of rare top quark production processes predicted by the Standard Model and has enabled searches for heavily suppressed flavour-changing-neutral-current interactions of the top quark. In this contribution the highlights are shown of searches by the ATLAS experiment for rare processes involving top quark. The associated top quark production processes of a top quark pair with Standard Model gauge bosons have been observed, as well as the tZq process, and provide tight constraints on the top quark electro-weak couplings. Recently, the ATLAS experiment has announced evidence for the four-top-production process, and has performed a combined measurement of the tttt cross section in the single-lepton, two-lepton and multi-lepton channels. Finally, results are presented of searches for flavour-changing-neutral-current processes involving top quarks.
Run 2 of the Large Hadron Collider, with 140/fb of proton proton collisions at a center-of-mass energy of 13 TeV, has produced over 10^8 top quarks. The large sample has enabled precise measurements of the production cross section in the "classical" top quark production processes, as well as new measurements in previously unobserved kinematic regimes and production processes. In this contribution, precision measurements of top quark properties and interactions are reviewed, with emphasis on the recent highlights of the ATLAS top quark physics program.
Measurements in top-antitop events at the LHC unraveled some anomalies. We examine the possibility that those reflect some mismodeling in Standard Model top pair-production. While subdominant, so-far neglected toponium contributions yield the additional production of dileptonic systems of small invariant mass and small azimuthal angle separation, which could explain the anomalies. We propose a method to discover toponium in present and future data. This paves the way to further experimental and phenomenological studies, as understanding toponium effects is essential for precision measurements of one of the most important parameters of the Standard Model, the top mass.
The vector bosons decaying into two same leptonic flavor and heavy-flavor jets have been studied using proton-proton collisions at the Large Hadron Collider with the CMS experiment. This study is important to test pQCD theory by comparing experimental cross section with theoretical predictions and to distinguish signal from the background in many SM processes and BSM searches. The kinematic properties have been compared with the prediction from several Monte Carlo event generators using different parton shower simulations.
The ATLAS experiment has performed measurements of B-meson rare decays proceeding via suppressed electroweak flavour changing neutral currents, and of mixing and CP violation in the neutral B meson systems.
This talk will focus on the latest results from the ATLAS collaboration, such as rare processes B^0_s → mu mu and B^0 → mu mu, and CP violation in the B_s^0 —> J/psi phi decays. In the latter, the Standard Model predicts the CP violating mixing phase, phi_s, to be very small and its SM value is very well constrained, while in many new physics models large phi_s values are expected. The latest measurements of phi_s and several other parameters describing the B_s^0 —> J/psi phi decays will be reported.
https://pitt.zoom.us/j/93687648384
The projected discovery and exclusion capabilities of searches are often quantified using the median expected $p$-value or its corresponding significance. However, this criterion can lead to flawed results, for example counterintuitively predicting lessened sensitivities if the experiment takes more data or reduces its background. We discuss the merits of several alternatives to the median expected significance, both when the background is known and when it is subject to some uncertainty. We advocate for standard use of the “exact Asimov significance” $Z^{\rm A}$ detailed in this talk.
With current high precision collider data and high-order calculations, the reliable estimation of theoretical uncertainty due to missing higher orders (MHO) terms has become a pressing issue for perturbative QFT predictions. The traditionally used simple but ad hoc scale variation has no probabilistic interpretation. Bayesian approach to MHO introduced by Cacciari and Houdeau and recently extended by Bonvini offers a promising alternative. In this paper, we thoroughly scrutinize the Bayesian approach and systematically study the performance of different models on an extensive set of high-order calculations.We extend the framework in two significant ways. First, we define three-parameter $abc$-model to allow for asymmetric probability distributions. Secondly, we calculate MHO uncertainty for scale-dependent quantities, treating different choices of the factorization and regularization scales democratically, without the hidden parameter interpretation à la Bonvini. We clarify how these two choices bias the result towards specific scale values. Finally, we provide a practical prescription of how existing perturbative results at the standard scale variation points can be converted to 68 %/95 % confidence intervals in the Bayesian approach.
Ref.: Claude Duhr, Alexander Huss, Aleksas Mazeliauskas, and Robert Szafron, to appear soon.
The trigger systems of the LHC detectors play a crucial role in determining the physics capabilities of the experiments. The CMS experiment implements a sophisticated two-level triggering system composed of the Level-1(L1), instrumented by custom-design hardware boards, and the High Level Trigger(HLT), a streamlined version of the offline reconstruction software running on a computer farm. For Phase2 of the LHC, the increase in the instantaneous luminosity and pile-up will raise the event rate to a level which is extremely challenging for the trigger algorithms. New approaches and optimizations have been studied to keep the trigger rate manageable while maintaining thresholds low enough to cover the needs of physics analyses. We will show the optimizations and improvements that are being done for Phase2 electron and photon triggers to allow pileup mitigation exploiting the highly granular calorimeter in endcap(HGCAL). Moreover, the addition of the tracker information at L1 and the enhanced computing resources at HLT will also help to maintain the trigger efficiency and thresholds in Phase2 at a similar level as Run2.
Sophisticated machine learning techniques have promising potential in search for physics beyond Standard Model (BSM) in Large Hadron Collider (LHC). Convolutional neural networks (CNN) can provide powerful tools for differentiating between patterns of calorimeter energy deposits by prompt particles of Standard Model and long-lived particles predicted in various models beyond the Standard Model. We demonstrate the usefulness of CNN by using a couple of physics examples from well motivated BSM scenarios predicting long-lived particles giving rise to displaced jets. Our work suggests that modern machine-learning techniques have the potential to discriminate between energy deposition patterns of prompt and long-lived particles, and thus, they can be useful tools in such searches.
In this paper we train a Convolutional Neural Network to classify longitudinally and transversely polarized hadronic $W^\pm$ using the images of boosted $W^{\pm}$ jets as input. The images capture angular and energy information from the jet constituents that is faithful to properties of the original quark/anti-quark $W^{\pm}$ decay products without the need for invasive substructure cuts. We find that the difference between the polarizations is too subtle for the network to be used as an event-by-event tagger. However, given an ensemble of $W^{\pm}$ events with unknown polarization, the average network output from that ensemble can be used to extract the longitudinal fraction $f_L$. We test the network on Standard Model $pp \to W^{\pm}Z$ events and on $pp \to W^{\pm}Z$ in the presence of dimension-6 operators that perturb the polarization composition.
Collider data analysis, which usually requires complicated software frameworks, has a very steep learning curve. Therefore, a sizable barrier exists between data and the physicist wishing to work on different analysis ideas. Recently, a new approach has been under development to address this issue and provide a practical way to collider data analysis. This approach features the so-called "Analysis Description Language" (ADL), a domain specific, declarative language capable of describing the contents of an LHC analysis in a standard and unambiguous way, independent of any computing frameworks. In ADL, analyses are written in human-readable text files, separating object, variable and event selection definitions in blocks. The ADL syntax includes mathematical and logical operations, comparison and optimisation operators, reducers, four-vector algebra and commonly used functions. ADL can be rendered executable on event data with any infrastructure capable of understanding its syntax. The first such complete infrastructure is the CutLang runtime interpreter, which can run ADL analyses on data witout any need for programming in a general purpose language. ADL and CutLang are designed for use in both experimental and phenomenological data analyses, and are also being integrated for use with the LHC Open Data. A number of LHC analyses have already been implemeted with ADL to form an analysis database for interpretation of experimental results or other phenomenology studies. ADL/CutLang also provde a practical setup to effectively perform collider sensitivity studies. This talk will introduce ADL and CutLang and their growing applications in different areas of collider analysis.
SModelS is an automatic, public python tool providing a fast reinterpretation of simplified model results from the LHC within any model of new physics respecting a Z_2 symmetry. We present the recently released v2.0 that includes a major revision of the decomposition algorithm. It introduces the particles’ decay widths and their quantum numbers as additional parameters of the simplified model topologies. This enables to incorporate a wide range of exotic signatures, such as searches for disappearing and kinked tracks, displaced jets and leptons as well as delayed jets and photons. In total, our database contains simplified models results of over 100 CMS and ATLAS publications including prompt and long-lived particle searches. We demonstrate the impact on various new physics scenarios motivated by dark matter.
Lately, interest has grown in forward, high $\eta$ physics with experiments like FASER and FORMOSA at the LHC. However, particle physics event generators like Pythia have primarily been calibrated to make predictions in the central, low $\eta$ regions. As such, predictions in the forward region are in tension with current forward physics data. It is imperative to obtain accurate particle productions, to fully utilize these novel forward experiments. In this talk I will discuss the progress we have made to tune Pythia for forward experiments. This tune will provide a practical tool to determine particle production rates in the forward region, and can be used to study neutrino interactions, BSM physics, and cosmic rays.
In this talk, we will introduce a technique to train neural networks into being good event variables, which are useful to an analysis over a range of values for the unknown parameters of a model.
We will use our technique to learn event variables for several common event topologies studied in colliders. We will demonstrate that the networks trained using our technique can mimic powerful, previously known event variables like invariant mass, transverse mass, and MT2.
We will describe how the machine learned event variables can go beyond the hand-derived event variables in terms of sensitivity, while retaining several attractive properties of event variables, including the robustness they offer against unknown modeling errors.
https://pitt.zoom.us/j/93951025550
https://pitt.zoom.us/j/93951025550
Many theories beyond the Standard Model predict new phenomena, such as Z’, W’ bosons, vector-like quarks, or heavy neutrinos. Searches for new physics in different final state signatures, produced either resonantly or non-resonantly, including a general search using multilepton final states are performed using the ATLAS experiment at the LHC. Lepton flavor violation (LVF) is a striking signature of potential beyond the Standard Model physics. The search for LFV with the ATLAS detector is reported in searches focusing on the decay of the Z boson into different flavour leptons (e/mu/tau). The most recent 13 TeV pp results will be reported.
We present results of searches for vector-like quarks using proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV. Single and pair production of vector-like quarks are studied, with decays into a variety of final states, containing top and bottom quarks, electroweak gauge and Higgs bosons. The presented searches make use of a wide variety of reconstructed objects, allowing to explore diverse signatures from multi-leptonic to fully hadronic. We set exclusion limits on the vector-like quark masses and cross sections, and for combinations of the vector-like quark branching ratios.
The bottom quark forward-backward asymmetry ($A_{FB}^b$) data at LEP exhibits a long-standing discrepancy with the standard model prediction.
We propose a novel method to probe the $Zb\bar{b}$ interactions through $gg\to Zh$ production at the LHC, which is sensitive to the axial-vector component of the $Zb\bar{b}$ couplings. We demonstrate that the $Zh$ data collected at the 13 TeV LHC can already resolve the apparent degeneracy of the anomalous $Zb\bar{b}$ couplings implied by the LEP precision electroweak measurements, with a strong dependence on the observed distribution of the $Z$ boson transverse momentum.
We also show the potential of the HL-LHC to either verify or exclude
the anomalous $Zb\bar{b}$ couplings observed at LEP through measuring the $Zh$ production rate
at the HL-LHC, and this conclusion is not sensitive to possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.
In many models that address the naturalness problem, top-quark partners are often postulated in order to cure the issue related to the quadratic corrections of the mass of the Higgs boson. In this work, we study alternative modes for the production of top- and bottom-quark partners ($T$ and $B$), $pp\rightarrow B$ and $pp\rightarrow T\bar{t}$, via a chromo-magnetic moment coupling. We adopt the simplest composite Higgs effective theory for the top-quark sector incorporating partial compositeness, and investigate the sensitivity of the 14 TeV LHC.
I will present precision predictions for scalar leptoquark pair production at hadron colliders. Apart from QCD contributions, included are the lepton t-channel exchange diagrams relevant in the light of the recent B-flavor anomalies. All contributions are evaluated at next-to-leading order in QCD and improved by resummation corrections, in the threshold regime, from soft-gluon radiation at next-to-next-to-leading-logarithmic accuracy. All corrections are found equally relevant. Furthermore, the impact of different sets of parton distribution functions will be discussed. These predictions consist of the most precise leptoquark cross section calculations available to date and are necessary for the best exploitation of leptoquark LHC searches.
Many new physics models, e.g., compositeness, extra dimensions, extended Higgs sectors, supersymmetric theories, and dark sector extensions, are expected to manifest themselves in the final states with leptons and photons. This talk presents searches in CMS for new phenomena in the final states that include leptons and photons, focusing on the recent results obtained using the full Run-II data-set collected at the LHC.
Leptoquarks (LQ) are predicted by many new physics theories to describe the similarities between the lepton and quark sectors of the Standard Model and offer an attractive potential explanation for the lepton flavour anomalies observed at LHCb and flavour factories. The ATLAS experiment has a broad program of direct searches for leptoquarks, coupling to the first-, second- or third-generation particles. This talk will present the most recent 13 TeV results on t he searches for leptoquarks and contact interactions with the ATLAS detector, covering flavour-diagonal and cross-generational final states.
We propose a novel possibility to detect a very distinctive signal with more than four muons originating from pair-produced vector-like leptons decaying to a muon-philic Z′ boson. These new particles are good candidates to explain the anomalies in the muon anomalous magnetic moment and the b→sℓℓ processes. The doublet (singlet) vector-like leptons lighter than 1.3 (1.0) TeV are excluded by the latest data at the LHC if BR(E→Z′μ)=1. We also show that the excess in the signal region with more than five leptons can be explained by this scenario if the vector-like lepton is a weak singlet, with mass about 400 GeV and BR(E→Z′μ)=0.25. The future prospects at the HL-LHC are discussed.
Recent precise determination of the electron anomalous magnetic moment (AMM) adds to the longstanding tension of the muon AMM and together strongly point towards physics beyond the Standard Model (BSM). Here we present a solution to both anomalies via a light scalar that emerges from a second Higgs doublet and resides in the $\mathcal{O}(10)$-MeV to $\mathcal{O}(1)$-GeV mass range. A scalar of this type is subject to a number of various experimental constraints, however, as we show, it can remain sufficiently light by evading all experimental bounds and has the great potential to be discovered in the near-future low-energy experiments. In addition to the light scalar, our theory predicts the existence of a nearly degenerate charged scalar and a pseudoscalar, which have masses of the order of the electroweak scale. This scenario can be tested at the LHC by looking at the novel process $pp \to H^\pm H^\pm jj \to l^\pm l^\pm j j + {E\!\!\!\!/}_{T}$ via same-sign pair production of charged Higgs bosons.
In certain extensions of the Standard Model(SM), the interactions between the new scalars and the SM Higgs can cause the electroweak(EW) symmetry to remain broken at temperatures well above the electroweak scale. Fermionic-induced EW symmetry non-restoration (EWSNR) effect has also been studied in the context of effective field theories, where EWSNR is linked to some non-renormalizable interactions; thus, fermionic-induced EWSNR only occurs below specific cutoff temperature. In this talk, I will introduce some UV-complete models with new fermions that have unstored EW symmetry at high temperatures. In these models, fermionic-induced EWSNR is not limited by a cutoff temperature because some of the heavy fermions are always decoupled from thermal equilibrium at high temperatures as a consequence of their mass mechanisms. Then, I will identify the parameter space that satisfies the theoretical (stability of effective potential, perturbative unitarity bound, thermal equilibrium conditions) and experimental constraints. Within this parameter space, I will examine the novel thermal histories of these models and their phenomenological implications.
Models of freeze-in dark matter that incorporate two or more dark matter mass eigenstates, typically below $\sim$100 keV, can simultaneously account for the observed baryon asymmetry, through the oscillations of the out-of-equilibrium dark matter particles. We consider the case in which the dark matter is produced by early-universe decays of electroweak-charged scalars, the lightest of which is typically in the few hundred GeV to few TeV range to realize the observed dark matter and baryon densities. Using a network of quantum kinetic equations that describe dark matter production, annihilation, and oscillations, along with washout and spectator processes, we find that the minimal model, with two dark matter mass eigenstates and a single scalar, is tightly constrained. Including Yukawa couplings of the scalar beyond its interaction with the dark matter or adding one or more additional scalars significantly expands the viable parameter space, much of which has the lightest scalar being long-lived at colliders. We discuss the model’s discovery potential at the Large Hadron Collider along with other possible experimental probes.
We introduce a new approach to the Higgs naturalness problem, where the value of the Higgs mass is tied to cosmic stability and the possibility of a large observable Universe. The Higgs mixes with the dilaton of a CFT sector whose true ground state has a large negative vacuum energy. If the Higgs VEV is non-zero and below ~TeV, the CFT also admits a second metastable vacuum, where the expansion history of the Universe is conventional. As a result, only Hubble patches with unnaturally small values of the Higgs mass support inflation and post-inflationary expansion, while all other patches rapidly crunch. The elementary Higgs VEV driving the dilaton potential is the essence of our new solution to the hierarchy problem. The main experimental prediction is a light dilaton field in the 0.1-10 GeV range that mixes with the Higgs. Part of the viable parameter space has already been probed by measurements of rare B-meson decays, and the rest will be fully explored by future colliders and experiments searching for light, weakly-coupled particles.
We study electroweak phase transition and resultant GWs of a CP conserving 2HDM with a softly broken $Z_2$ symmetry. We analysed the parameter space of both type I and type II 2hdm without relying on any decoupling limit. We observe $M_{H^\pm} \approx M_H$ or $M_{H^\pm} \approx M_A$ favours SFOEWPT in 2HDM. In addition to di-Higgs production, scalar to fermion decay channel is also important to probe phase transition behaviour in 2HDM. We also comment about the shape of potential leading to SFOEWPT in 2hdm.
The Standard Model (SM) vacuum is unstable for the measured values of the
top Yukawa coupling and Higgs mass. We study the issue of vacuum stability
when neutrino masses are generated through spontaneous low-scale lepton number
violation. In the simplest dynamical inverse seesaw, the SM Higgs has two siblings: a massive CP -even scalar plus a massless Nambu-Goldstone boson, called majoron. For TeV scale breaking of lepton number, Higgs bosons can have a sizeable decay into the invisible majorons. We examine the interplay and complementarity of vacuum stability and perturbativity restrictions, with collider constraints on visible and invisible Higgs boson decay channels. This simple framework may help guiding further studies, for example, at the proposed FCC facility.
We study the effect of interference on the lepton number violating (LNV) and lepton number conserving (LNC) three-body meson decays $M^+_1 → l^+_i l^±_j π^∓$, that arise in a TeV scale Left Right Symmetric model (LRSM) with degenerate or nearly degenerate right handed (RH) neutrinos. LRSM contains three RH neutrinos and a RH gauge boson. The RH neutrinos with masses in the range of $M_N$$∼$(MeV - few GeV) can give resonant enhancement in the semi-leptonic LNV and LNC meson decays. In the case, where only one RH neutrino contributes to these decays, the predicted new physics branching ratio of semi-leptonic LNV and LNC meson decays $M^+_1 → l^+_i l^+_j π^−$ and $M^+_1 → l^+_i l^−_j π^+$ are equal. We find that with at least two RH neutrinos contributing to the process, the LNV and LNC decay rates can differ. Depending on the neutrino mixing angles and CP violating phases, the branching ratios of LNV and LNC decay channels mediated by the heavy neutrinos can be either enhanced or suppressed, and the ratio of these two rates can differ from unity.
Explaining the tiny neutrino masses and non-zero mixings have been one of the key motivations for going beyond the framework of the Standard Model (SM). We discuss a collider testable model for generating neutrino masses and mixings via radiative seesaw mechanism. That the model does not require any additional symmetry to forbid tree-level seesaws makes its collider phenomenology interesting. The model includes multi-charged fermions/scalars at the TeV scale to realize the Weinberg operator at 1-loop level. After deriving the constraints on the model parameters resulting from the neutrino oscillation data as well as from the upper bound on the absolute neutrino mass scale, we discuss the production, decay and resulting collider signatures of these TeV scale fermions/scalars at the Large Hadron Collider (LHC). We consider both Drell-Yan and photo-production. The bounds from the neutrino data indicate the possible presence of a long-lived multi-charged particle (MCP) in this model. We obtain bounds on these long-lived MCP masses from the ATLAS search for abnormally large ionization signature. When the TeV scale fermions/scalars undergo prompt decay, we focus on the 4-lepton final states and obtain bounds from different ATLAS 4-lepton searches.
https://pitt.zoom.us/j/91379044495
Axion couplings to photons could induce photon-axion conversion in the presence of magnetic fields in the Universe. The conversion could impact various cosmic distance measurements such as luminosity distances to type Ia supernovae and angular distances to galaxy clusters in different ways. We consider different combinations of the most updated distance measurements to constrain the axion-photon coupling. Ignoring the conversion in intracluster medium (ICM), we find the upper bounds on axion-photon couplings to be around $5 \times 10^{−12} ~({\rm nG}/B)~ {\rm GeV}^{−1}$ for axion mass below $5 \times 10^{−13}~ {\rm eV}$, where B is the strength of the magnetic field in the intergalactic medium (IGM). When including the conversion in ICM, the upper bound gets stronger and could be as strong as $5 \times 10^{−13} ~ \mathrm{GeV}^{−1}$ for $m_a < 5 \times 10^{−12} ~ \mathrm{eV}$. While this stronger bound depends on the ICM modeling moderately, it is independent of the IGM parameters.
A number of proposed and ongoing experiments search for axion dark matter with a mass nearing the limit set by small scale structure. I will discuss the late universe cosmology of these models and show that requiring the axion to have a matter-power spectrum that matches that of cold dark matter constrains the magnitude of the axion couplings to the visible sector. I will also survey mechanisms that can alleviate the bounds, namely, the introduction of large charges, various forms of kinetic mixing, a clockwork structure, and imposing a discrete symmetry. We provide an explicit model for each case and explore their phenomenology and viability to produce detectable ultralight axion dark matter.
Ultralight axions (ULA), whose masses can lie in a wide range of values and can be even smaller than $10^{-28}$ eV, are generically predicted in UV theories such as string theory. In the cosmological context, the early Universe may have gotten filled with a network of ultralight axion (ULA) cosmic strings which, depending upon the mass of the axion, can survive till very late times. If the ULA also couples to electromagnetism, and the network survives post recombination, then the interaction between the strings and the CMB photons induces a rotation of the polarization axis of the CMB photons (otherwise known as the birefringence effect). This effect is independent of the string tension, and only depends on the coupling between the ULA and the photon (which in turn is sensitive to UV physics). In this talk I will present some results for this birefringence effect on CMB, due to three different models of string network. Interestingly, this is within the reach of some current and future CMB experiments.
Axion-like particles (ALPs) play an important role for inflationary model building, as well as are well motivated dark matter candidates. The out-of-equilibrium initial conditions, combined with their possibly nontrivial potentials, allow for a rich nonlinear dynamics of such fields in the early universe.
We consider the coherent oscillations of an ALP field in a wiggly potential and investigate the scenario when the fluctuations on top of the homogeneous field are amplified via parametric instabilities, leading to the complete fragmentation of the field. If the potential contains several local minima, separated by barriers, transitions between such minima can be induced via bubble nucleation. We investigate such transitions, taking into account the dynamical, nonthermal nature of the process and the impact of fragmentation. The above mentioned processes are accompanied by the production of a stochastic gravitational wave background, possibly within reach of future detectors.
Axions, if they exist, can be produced efficiently in white dwarfs, free-stream out of the star due to their weak interactions with matter, and then be converted to a photon in the stellar magnetosphere. X-ray telescope observations of these stars can provide strong constraints on the coupling to electromagnetism and matter. I discuss the results of the first dedicated observation of a magnetic white dwarf in hard X-rays, and what it tells us about axions.
Neutrino self-interaction has been proposed as a solution to the Hubble tension, a discrepancy between the measured values of the Hubble constant from CMB and low-redshift data. However, flavor-universal neutrino self-interaction is highly constrained by BBN and laboratory experiments such as K-meson and tau decay, double-neutrino beta decay etc. In this talk, I will discuss the cosmology of flavor specific neutrino self-interaction where only one or two neutrino flavor states are self-interacting. Such flavor-specific interactions are less constrained by the laboratory experiments. I will show that CMB and other cosmological dataset favours strong flavor specific neutrino self-interaction. Finally, I will talk about the feasibility of addressing the Hubble tension in this framework.
If neutrino self-interactions arise from beyond-Standard Model physics, there will be scattering between astrophysical and cosmic background neutrinos. As a result, resonance features can appear in astrophysical neutrino spectra. While the flavor-diagonal case has been studied before numerically, we present an analytic result for arbitrary self-coupling matrix, allowing for possibilities such as self-interactions only between tau neutrinos. We then examine effects on the diffuse supernova neutrino background and high-energy astrophysical neutrinos.
We show that a minimal local B−L symmetry extension of the standard model can provide a unified description of both neutrino mass and dark matter. In our model, B−L breaking is responsible for neutrino masses via the seesaw mechanism, whereas the real part of the B−L breaking Higgs field (called σ here) plays the role of a freeze-in dark matter candidate for a wide parameter range. Since the σ-particle is unstable, for it to qualify as dark matter, its lifetime must be longer than 1025 seconds implying that the B−L gauge coupling must be very small. This in turn implies that the dark matter relic density must arise from the freeze-in mechanism. The dark matter lifetime bound combined with dark matter relic density gives a lower bound on the B−L gauge boson mass in terms of the dark matter mass. We point out parameter domains where the dark matter mass can be both in the keV to MeV range as well as in the PeV range. We discuss ways to test some parameter ranges of this scenario in collider experiments. Finally, we show that if instead of B−L, we consider the extra U(1) generator to be −4I3R+3(B−L), the basic phenomenology remains unaltered and for certain gauge coupling ranges, the model can be embedded into a five dimensional SO(10) grand unified theory.
If dark matter particles interact too feebly with ordinary matter, they have never been able to thermalize in the early universe. Such Feebly Interacting Massive Particles (FIMPs) would be therefore produced via the freeze-in mechanism. Testing FIMPs is a challenging task, given the smallness of their couplings. In this talk, after giving a brief overview on the phenomenology of FIMPs, I will discuss our recent proposal of a $ Z'$ portal where the freeze-in can be currently tested by many experiments. In our model, $ Z'$ bosons with mass in the MeV-PeV range have both vector and axial couplings to ordinary and dark fermions. We constraint our parameter space with bounds from direct detection, atomic parity violation, leptonic anomalous magnetic moments, neutrino-electron scattering, collider, and beam dump experiments.
We present a study of spin-2 mediated scalar dark matter. As a blueprint, we work in a warped extra-dimensional model such that the mediator(s) are the massive spin-2 Kaluza-Klein (KK) modes of the 5D graviton. On top of Standard Model particles, we focus on dark matter annihilations into KK-gravitons. Due to the longitudinal modes of the massive gravitons, any truncation of the KK-tower leads to a tremendous growth of the amplitude at large center of mass energies $\sqrt{s}$, which heavily impacts any phenomenological analysis. For the first time, we include the full KK-tower in this dark matter production process and find that this growth is unphysical and cancels once the full field content of the extra-dimensional theory is taken into account. Interestingly, this implies that it is not possible to approximate the results obtained in the full theory with a reduced set of effective interactions once $\sqrt{s}$ is greater than the lightest massive graviton. This casts some doubt on the universal applicability of previous studies with spin-2 mediators within an EFT framework and prompts us to revisit the phenomenological allowed parameter space.
A particularly salient aspect of particle dark matter models is the connection between thermal interactions and cosmological abundance. Extending from the famous WIMP paradigm is a rich sector of dark sector models with different number changing mechanisms, all of which realize a relic abundance via interactions with the Standard Model or itself. In this talk I will introduce one of these scenarios: Co-SIMP dark matter, whose key interactions involve both cannibalistic interactions and couplings to the Standard Model. I will discuss the phenomenology and UV completions of this scenario, as well as constraints and prospects for detection.
The idea of with EW-$\nu_R$ model with additional GeV scale mirror fermions with large displaced vertices and extended Scalar sector is very appealing from the Collider perspective. The presence of a complex singlet scalar in this model helps to solve the strong-CP problem, satisfying the constraint coming from the present absence of neutron electric dipole moment, and without need of an axion.
Based on this model, in this work, we study the detailed scalar mass spectrum, having $\sim 125$ GeV Higgs-like scalar, which is allowed by the signal strength and lepton flavor violating constraints data. Besides explaining the $\sim 125$ GeV Higgs-like scalar, this scenario can also accommodate a non-thermal scalar dark matter candidate that can satisfy the relic density data.
The imaginary part of the complex singlet scalar in this model serves as a viable non-thermal feebly interacting massive particle (FIMP) dark matter candidate.
We identify the region of the parameter space for the freeze-in scenario, which is consistent with all the bounds from relic density and direct-indirect searches and discuss the possible future implications of this scenario.
Extensions of the two higgs doublet models with a singlet scalar can easily accommodate all current experimental constraints and are highly motivated candidates for Beyond Standard Model Physics. It can successfully provide a dark matter candidate, explain baryogenesis and provide gravitational wave signals. In this work, we focus on the dark matter phenomenology of the two higgs doublet model extended with a complex scalar singlet which serves as the dark matter candidate. We study the variations of the dark matter observables, ie, relic density and direct detection cross-section, with respect to the model parameters. We obtain a few benchmark points in the light and heavy dark matter mass region. We are also currently studying possible signatures of this model at current and future colliders and the possibility to distinguish this model from other new physics scenarios.
In this talk, we propose a new electroweakly interacting spin-1 dark matter (DM) model. We consider the non-Abelian extension of electroweak symmetry. Namely, we extend the SU(2)$_L$ group in the Standard Model (SM) into the direct products of three SU(2) groups. We also impose the exchange symmetry between two of these SU(2) groups to realize the spin-1 stable spectrum. In this setup, the DM pair efficiently annihilate into SM particles through the electroweak interaction. Therefore, we can obtain the DM energy density correctly via the freeze-out mechanism. We also find not only electroweak processes but also Higgs exchange processes give the relevant contribution to determine the DM energy density. We conclude a next-generation DM searches will be an excellent probe of this spin-1 DM.
Dark matter self-interactions have been proposed as a solution to various astrophysical small-scale structure anomalies. We explore the scenario in which dark matter self-interacts through a continuum of low-mass states. This happens if dark matter couples to a strongly-coupled nearly-conformal hidden sector. This type of theory is holographically described by brane-localized dark matter interacting with bulk fields in a slice of 5D anti-de Sitter space. The long-range potential in this scenario depends on a non-integer power of the spatial separation. We find that continuum mediators introduce novel power-law scalings for the scattering cross section, opening new possibilities for dark matter self-interaction phenomenology.
https://pitt.zoom.us/j/97533519613
In R-parity violating supersymmetric scenario, assuming the third-generation superpartners to be the lightest (calling the scenario RPV3), we show that there are some benchmark scenarios in which $R_{D^{(*)}}$ and / or $R_{K^{(*)}}$ and / or $(g-2)_{\mu}$ anomalies can be addressed and also can be detected at LHC 14 TeV or future 27 TeV hadron collider. We consider $\overline{t}\tau\overline{\tau}$ or $\overline{t}\mu\overline{\mu}$ for different cases as our final states to be detected at colliders because there is no simple Standard Model (SM) process can have this kind of final state and the background cross-section is thus very small.
The NA62 experiment at CERN collected a large sample of charged kaon decays into final states with multiple charged particles in 2016-2018. This sample provides sensitivities to rare decays with branching ratios as low as 10-11. Searches for lepton flavour and lepton number violating decays of the charged kaon into final states containing a lepton pair based on this data set are presented.
Flavourful Feebly-Interacting Particles (FIPs) in the MeV to GeV range have a strong impact on precision frontier observables ranging from rare meson decays to the lepton anomalous magnetic moments. We use an effective field theory approach “SM+X” along with the HEPfit package to study the effect of FIPs on B to K observables. We present an updated study of the available parameter space and constraints, focusing on FIP scenarios allowing for a simultaneous fit of both the $R_{K^{(*)}}$ and the $(g-2)_{\mu}$ anomalies. We further present an explicit UV realization.
A Left-Right Symmetric Model which utilizes vector-like fermions to generate quark and lepton masses via universal see-saw mechanism is studied. In this talk, I will present the results of our analysis on the new contributions to flavor observables from this model. Further, I will discuss the possibilities of explaining the neutral current B-anomalies as well as the Cabibbo anomaly in this model.
Scenarios in which right-handed light Standard Model fermions couple to a new gauge group, $U(1)_{T3R}$ can naturally generate a sub-GeV dark matter candidate. But such models necessarily have large couplings to the Standard Model, generally yielding tight experimental constraints. We show that the contributions to $g_\mu-2$ from the dark photon and dark Higgs largely cancel out in the narrow window where all the experimental constraints are satisfied, leaving a net correction which is consistent with recent measurements from Fermilab.These models inherently violate lepton universality, and UV completions of these models can include quark flavor violation which can explain $R_{K^{(\ast)}}$ anomalies as observed at the LHCb experiment after satisfying the $B_s\rightarrow\mu\mu$ constraint in the allowed parameter space of the model. This scenario can be probed by FASER, SeaQuest, SHiP, LHCb, Belle etc.
$b\to s\tau\tau$ and $b\to c\tau \nu$ measurements are highly motivated for addressing lepton-flavor-universality-violating (LFUV) puzzles, such as $R_{D^{(*)}}$, $R_{J/\psi}$ and $R_{K^{(\ast)}}$ anomalies, raised by the data of LHCb, BELLE and BarBar. The planned operation of future $e^-e^+$ colliders as a $Z$ factory provides a great opportunity to conduct such measurements, because of its relatively high production rates and reconstruction efficiency for $B$ mesons at $Z$ pole. In this project we will pursue a systematic sensitivity study on these measurements at future $Z$ factories. The implications of the outcomes for LFUV new physics will be also explored.
The latest results on the production of Higgs boson pairs (HH) in the ATLAS experiment are reported, with emphasis on searches based on the full LHC Run-2 dataset at 13 TeV. In the case of non-resonant HH searches, results are interpreted both in terms of sensitivity to the Standard Model and as limits on kappa_lambda, i.e. a modifier of the Higgs boson self-coupling strength. Searches for new resonances decaying into pairs of Higgs bosons are also reported. Prospects of testing the Higgs boson self-coupling at the High Luminosity LHC (HL-LHC) will also be presented
In this talk, we compute the loop corrections to the single Higgs production and decay rates coming from 4 fermion operators of the third generation quarks, which could be tested by current and future ATLAS and CMS measurements of these processes.
These operators have sizeable effects to gluon fusion, $t\bar{t} H$ production cross-sections, as well as Higgs decays to gluons, photons and bottom quarks.
Indeed, we find that for some SM effective Field Theory operators and with the precision of current combined ATLAS and CMS Higgs data, those effects can strengthen the existing bounds from global fits to other processes.
Moreover, since single Higgs processes have been used to constrain the trilinear Higgs self-coupling, we study the correlation between this coupling and the 4 fermion operators fits.
While precision measurements of the Higgs at the LHC continue to confirm its Standard Model-like nature, many of its properties, in particular its couplings to light quarks and to itself, remain essentially unconstrained. Di-Higgs production is well known to be a direct probe of the self coupling, but as I will argue, it is also a powerful probe of Higgs flavor. In models where enhanced Yukawas arise from new scalars with large couplings to light quarks, gigantic di-Higgs — and even tri-Higgs — production rates can be obtained, which can be used to constrain or discover these theories. In this talk, I’ll motivate such theories and describe how they avoid constraints from flavor while enhancing the Higgs Yukawa couplings to light quarks by orders of magnitude. I will then demonstrate that Multi-Higgs production is the most stringent constraint on the Higgs Yukawas in this context, setting limits on the down Yukawa at roughly 30 times its Standard Model value. I will also show that the currently unexplored triple Higgs production topology could be a potential discovery channel for a variety of extended Higgs sectors at the LHC — including not only models where extra Higgses couple to light quarks, but also popular theories where they couple predominantly to the the top quark.
The recent searches for non-resonant and resonant Higgs pair production with various final states are presented. The analyses are performed using data collected by Compact Muon Solenoid detector with the proton-proton collisions at 13 TeV centre-of-mass energy during the Run2 period. The non-resonant analyses emphasise the results of the cross-section for Higgs pair production and various coupling parameters. For the resonant analyses, the model-independent approach is used, and the status of resolved and boosted topologies is reported together with their BSM models' implication.
Abstract: We examine the weak boson fusion (WBF) production of exotic heavy Higgs states with subsequent decay into 125 GeV Higgs bosons. We include contributions from the gluon fusion production channel and study the interplay of both production modes to improve the discovery potential at the LHC. We observe that in scenarios with isospin singlet mixing in the Higgs sector, resonant di-Higgs production in the WBF mode becomes a phenomenologically relevant channel at small mixing angles, and the inclusion of weak boson sideline can lead to a sizeable improvement in the discovery potential.
We distinguish two separate sources of CP-violation in a 2HDM: in the CP properties of the mass eigenstates, and in their bosonic interactions. A systematic study of the interplay between Higgs alignment and CP-violation enables us to define a scenario where departures from Higgs alignment could be present independently of CP-violation. Without recourse to the typically required angular correlations or electric dipole moment signals, and considering current experimental constraints, we suggest a smoking-gun signal of CP-violation in the Higgs-to-Higgs decay, (h3 → h2h1), where h3,h2, and h1 are the heaviest, second heaviest and the SM-like neutral Higgs bosons, respectively. The mere presence of this decay channel, which is non-zero only away from the alignment limit, is sufficient to establish CP-violation in a complex two-Higgs-doublet model. A distinct discovery channel lies in final states with three 125 GeV Higgs bosons, which has yet to be searched for, and could be detected at the high-luminosity LHC.
A common assumption about the early universe is that it underwent an electroweak phase transition (EWPT). Though the standard model (SM) is able to restore the electroweak symmetry through a smooth cross over PT, we require a strongly first-order PT to ensure electroweak baryogenesis, requiring us to look at new physics beyond the SM. The simplest case to extend the SM is to add a real singlet field, which allows for a first-order EWPTs (FOEPT) to occur.
Starting with the most general higgs+singlet lagrangian, we fixed four of its coupling constants as functions of the three quartics, the singlet and higg's mass and vacuum expectation value, whose range of values had more experimental motivation than the former. We ran a Monte-Carlo scan over these five free parameters, requiring a FOEPT and a PT strength of $\frac{v_c}{T_c}>1.3$. These points were then passed through the FindBounce package to calculate the nucleation temperature. The resulting parameter space was studied, most notably, we observed the ratio of the triple higgs coupling to the SM value $\left(\kappa =\lambda_3/\lambda_3^{SM}\right)$ take on values between 0.2 and 2.7. The possible values of $\lambda_3$ could serve as motivation for future collider experiments to improve sensitivity in this range when looking at the cross sections of $pp\rightarrow hh$ versus $\lambda_3$.
SU(2) triplet Higgs boson with Y=0 hyper charge breaks the custodial symmetry leading to a tree-level vertex with Z and W boson. This prompts the decays into ZW as compared to t b in a doublet charged Higgs case. However, additional Z_2 symmetry can make this triplet as inert leading to displaced mono/di-leptonic signatures. In case of complex triplet, the model produces a pure triplet dark matter along with a pure and mixed triplet charged Higgs bosons. The last scenario this gives rise to both the displaced and the prompt charged leptons in the final states. We try to distinguish such scenarios at the LHC.
We investigate a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. For this the Minimal Supersymmetric Standard Model is extended by adding light right-handed neutrinos and their superpartners, the R-sneutrinos. Moreover, we consider the lightest neutralinos to be higgsino-like. We first update a previous analysis and assess to which extent does existing LHC data constrain the allowed slepton masses. Here we find scenarios where sleptons with masses as low as 175 GeV are consistent with existing data. However, we also show that the up-coming run will either discover or rule out sleptons with masses of 300 GeV, even for these challenging scenarios.
We then take a scenario which is on the borderline of observability of the upcoming LHC run assuming a luminosity of 300 fb$^{−1}$. We demonstrate that a prospective international $e^+e^−$ linear collider with a center of mass energy of 1 TeV will be able to discover sleptons in scenarios which are difficult for the LHC. Moreover, we also show that a measurement of the spectrum will be possible within 1-3 per-cent accuracy.
We investigate flavored gauge mediation models in which the Higgs and messenger doublets are embedded in multiplets of the discrete non-Abelian symmetry $\mathcal{S}_3$. In these theories, the $\mathcal{S}_3$ symmetry correlates the flavor structure of the quark and lepton Yukawa couplings with the structure of the messenger Yukawa couplings that contribute to the soft supersymmetry breaking mass parameters. We provide a systematic exploration of possible scenarios within this framework that lead to the needed hierarchical quark and charged lepton masses, and examine the resulting phenomenological implications in each case. Quite generally, we find a split spectrum for the superpartner masses compared to flavored gauge mediation models controlled by Abelian symmetries, due to the need in our scenarios for two pairs of messenger fields. We also demonstrate that the flavor violation that is expected in these scenarios generally falls within phenomenologically viable ranges.
In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous R symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.
We present a phenomenological investigation of color-octet
scalars (sgluons) in supersymmetric models with Dirac gaugino masses that feature an explicitly broken $R$ symmetry ($R$-broken models). We have constructed such models by augmenting minimal $R$-symmetric models with a set of supersymmetric and softly supersymmetry-breaking operators that explicitly break $R$ symmetry. We have found new features that appear as a result of $R$ symmetry breaking, including enhancements to extant decay rates, novel tree- and loop-level decays, and improved cross sections of single sgluon production. We have also explored constraints on these models from the Large Hadron Collider. We find that, in general, $R$ symmetry breaking quantitatively affects existing limits on color-octet scalars, closing loopholes for light CP-odd (pseudoscalar) sgluons while perhaps opening one for a light CP-even (scalar) particle. Altogether, scenarios with broken $R$ symmetry and two sgluons at or below the TeV scale can be accommodated by existing searches.
Recent work on calculating string theory landscape statistical predictions for the Higgs and sparticle mass spectrum from an assumed power-law soft term distribution yields an expectation for m(h)~ 125 GeV with sparticles (save light higgsinos) somewhat beyond reach of high-luminosity LHC. A recent examination of statistics of SUSY breaking in IIB string models with stabilized moduli suggests a power-law for models based on KKLT stabilization and uplifting while models based on large-volume scenario (LVS) instead yield an expected logarithmic soft term distribution. We evaluate statistical distributions for Higgs and sparticle masses from the landscape with a log soft term distribution and find the Higgs mass still peaks around ~125 GeV with sparticles beyond LHC reach, albeit with somewhat softer distributions than those arising from a power-law.
models of dynamical SUSY breaking (DSB)-- with a hidden sector
gauge coupling g^2 scanned uniformly-- lead to gaugino condensation
and a uniform distribution of soft parameters on a log scale.
Then soft terms are expected to be distributed as m_{soft}^{-1}
favoring small values.
A scan of DSB soft terms generally leads to m_h<< 125 GeV
and sparticle masses usually below LHC limits.
Thus, the DSB landscape scenario seems excluded from LHC search results.
An alternative is that the exponential suppression of the weak scale is
set anthropically on the landscape via the atomic principle.
The statistics of the supersymmetry breaking scale in the string landscape has been extensively studied in the past finding either a power-law behaviour induced by uniform distributions of F-terms or a logarithmic distribution motivated by dynamical supersymmetry breaking. These studies focused mainly on type IIB flux compactifications but did not systematically incorporate the Kähler moduli. In this talk I point out that the inclusion of the Kähler moduli is crucial to understand the distribution of the supersymmetry breaking scale in the landscape since in general one obtains unstable vacua when the F-terms of the dilaton and the complex structure moduli are larger than the F- terms of the Kähler moduli. After taking Kähler moduli stabilisation into account, we find that the distribution of the gravitino mass and the soft terms is power-law only in KKLT and perturbatively stabilised vacua which therefore favour high scale supersymmetry. On the other hand, LVS vacua feature a logarithmic distribution of soft terms and thus a preference for lower scales of supersymmetry breaking. Whether the landscape of type IIB flux vacua predicts a logarithmic or power-law distribution of the supersymmetry breaking scale thus depends on the relative preponderance of LVS and KKLT vacua.
Measurements at colliders are often done by fitting data to simulations, which depend on many physical and unphysical parameters. One example is the top-quark mass, where parameters in simulation must be profiled when fitting the top-quark mass parameter. In particular, the dependence of top-quark mass fits on simulation parameters contributes to the error in the best measurements of the top-quark mass. In this talk, I discuss a simple new fitting method to reduce this error, where regression is done directly on ensembles of events. This method is superior at reducing the top-quark mass uncertainty when compared to both traditional histogram fitting methods as well as the modern ML DCTR method. More generally, machine learning from ensembles for parameter estimation has broad potential for collider physics measurements.
Fundamental spinless particles are theoretically common yet experimentally rare. This talk presents an overview of my recent phenomenology program probing enigmatic spin 0 dynamics sensitive to new physics. The Higgs self-coupling may remarkably become directly accessible soon but LHC challenges demand continued innovation. Meanwhile, scalar leptons elegantly reconcile the muon g–2 tension and dark matter, and colliding light could enable decisive searches. Tau g–2 is equally important but often overlooked, where new physics modifications generically involve the Higgs field in SMEFT. Finally, axion searches are expanding beyond cavity haloscopes with interesting R&D proposals for broadband sensitivity near the THz window.
In this talk we will discuss a recent study of a low-mass vector dark matter
candidate, $W'$, accompanied by a dark photon and dark $Z'$ in the context of a
simplified gauged two-Higgs-doublet model. The parameter space of the model
(allowed by experimental and theoretical constraints) indicates that a dark $Z'$
can be important for dark matter annihilation while a dark photon is crucial
for direct detection. Furthermore, the currently allowed parameter space can
be probed in the near future by sub-GeV dark matter experiments like CDEX,
NEWS-G and SuperCDMS.
Dark gauge bosons including dark photon and $Z'$ have been important players in beyond-the-Standard-Model phenomenology including their potential connection to dark matter. However, their feeble interactions with the Standard Model (SM) particles motivate the use of high-intensity beam-based experiments including neutrino experiments. If neutrinos are non-trivially charged under such dark gauge bosons, the neutrino scattering can be a good channel of investigating their existence, as the scattering may arise via an exchange of a dark gauge boson. In my talk, I will revisit this interesting possibility at a couple of neutrino experiments, DUNE and JSNS$^2$, in the neutrino-electron scattering channel, carefully taking into account the interference effect between the SM processes and new physics contributions, and show that these experiments can probe regions of parameter space that have never been explored before. I will point out that remarkably the destructive interference effect enables us to investigate their parameter space by deficit especially in beam-focusing neutrino experiments such as DUNE.
We study the potential of future Parity-Violating Electron Scattering (PVES) data to probe the parameter space of the Standard Model Effective Field Theory (SMEFT). We contrast the constraints derived from Drell-Yan data taken at the Large Hadron Collider (LHC) with projections of the planned PVES experiments SoLID and P2. We show that the PVES data can complement the bounds set by the LHC data in the dimension-6 operator space since it probes different combinations of operators than Drell-Yan. The lower characteristic energy of P2 and SoLID also helps disentangle effects of dimension-6 and dimension-8 operators that are difficult to resolve with LHC Drell-Yan data alone.
The dark matter experiment XENON1T reported recently an excess in electronic recoil events with a significance of 3.5 $\sigma$. Also, the Muon g-2 experiment at FERMILAB has confirmed the muon magnetic moment anomaly, raising the significance to 4.2 $\sigma$. Motivated by these experimental results, we interpret the signals in terms of a new light $Z ^\prime$ gauge boson. We discuss how such a light $Z ^\prime$ emerges in a Two Higgs Doublet Model augmented by an abelian gauge symmetry, in agreement with existing bounds.
In this talk, I will present the theoretical framework to probe dark sectors that have portal interactions with the standard model, mediated by irrelevant operators. The focus is to develop a model-independent approach, without any specific model biases. I will focus on dark sectors with approximate conformal dynamics, and elucidate how this allows model-independent bounds to be derived. I will present the constraints from the various class of experiments and explain the procedures and assumptions involved.
The general picture that emerges is that these sectors are poorly constrained at the moment and points to the kind of future experimental facilities that will improve the reach on such dark sectors.
(based on 2012.08537)
Collider searches for electroweak final states from decays involving narrow mass gaps in a new physics sector are kinematically limited by softness of the scattering products. In a prior study, we required a hard initial state jet in order to boost the visible system, and exploited variations in angular separations to suppress topologically identical backgrounds from WW+jets. Presently, we revisit that analysis to establish how much improvement may be realized by the application of machine learning techniques. We provide a boosted decision tree (BDT) with a combination of high-level (e.g. ditau invariant mass, MT2, cos-theta-star), and low-level (e.g. angular separations, PT ratios) variables. We find that the BDT functions most efficiently if “obvious” event selections (e.g. MET, dilepton Z-window) are applied at the outset, and if individual trainings against similar backgrounds are merged into a composite classification score. This approach yields significantly stronger background suppression and signal retention than could be achieved with manual optimization of cuts.
Many scenarios of physics beyond the Standard Model predict new particles with masses well below the electroweak scale. Low-energy, high luminosity colliders such as BABAR are ideally suited to discoverthese particles. We present several recent searches for low-mass dark sector particles at BABAR, including leptophilic scalars, self-interacting dark matter, and axion like particles produced in B decays. These examples demonstrate the importance of B-factories in fully exploring low-mass new physics.
A rich physics program remains unexplored in the far-forward region at the LHC. The Forward Physics Facility (FPF) is a proposal to enlarge an existing cavern in the far-forward region of ATLAS to house a suite of experiments with groundbreaking new capabilities for neutrinos, long-lived particle searches, milli-charged particle searches, QCD, dark matter, dark sectors, and cosmic rays. The FPF will be located 500 m from the ATLAS interaction point. It is shielded from the ATLAS interaction point by 100 m of concrete and rock, creating an extremely low-background environment, ideal for many standard model studies and new physics searches. In this talk, we describe the FPF’s location and general features, its physics potential in the HL-LHC era, and topics for further study.
We revisit a class of U(1) anomaly-free models that address the proton charge radius discrepancy in light of the latest (g-2) results for the muon.
In this talk, I’ll discuss about the production of baryon asymmetry through resonant leptogenesis and phenomological signatures of type-I seesaw scenario with a flavour and a CP symmetry that strongly constrains lepton mixing angles, and both low- and high-energy CP phases. I’ll specially focus on the effect of these symmetries on the collider signals in minimal B-L model and effective neutrino mass in neutrinoless double beta decay, while also requiring production of the experimentally observed baryon asymmetry ($\eta_B$).
The $U_1$ leptoquark is a suitable candidate to explain the persistent anomalies in the semileptonic decays of the $B$ meson. In this talk, I will discuss how we can use the LHC data to constrain the $U_1$ models. Since the LHC is sensitive towards the leptoquark couplings, rather than the Wilson coefficients, I will discuss some simple scenarios with different couplings that can contribute to the relevant operators and show that the LHC data either rule out or severely constrain these simple $U_1$ scenarios. I will also discuss how the limits can be drawn on scenarios with multiple nonzero couplings from the high-$P_T$ dilepton data. I will show how a TeV range $U_1$ can evade the dilepton limits and the direct search bounds and explain the anomalies.
We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(\star)}}$ and $R_{K^{(\star)}}$, as well as in muon $g-2$ measurement, $\Delta a_\mu$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(\star)}}$, $R_{K^{(\star)}}$ and $\Delta a_\mu$ within $1\, \sigma$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the $S_3$ LQ, which enhances its reach to 1.1 (6.2) TeV at $\sqrt s=14$ TeV high-luminosity LHC ($\sqrt s=100$ TeV FCC-hh). We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to $\Delta a_\mu$ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2--6)\% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.
Relevant information from collision events from the Large Hadron Collider (LHC) and other colliders can be represented as spatial data in the appropriate phase space. Features such as sharp discontinuities in the event number density may signal the presence of new physics. Extraction of features from the data relies upon estimation of the functional value of the underlying distribution. We attempt to use properties of the Voronoi tessellation of the data along with Machine Learning techniques to improve upon traditional methods of density estimation.
In a recent work, a successful prediction has been made for $\sin^2 \theta_W$ at an energy scale of O(TeV) based on the Dirac quantization condition of an electroweak monopole of the EW-$\nu_R$ model. The fact that such a prediction can be made has prompted the following question: Can $SU(2)$ be unified with $U(1)$ at O(TeV) scale since a prediction for $\sin^2 \theta_W$ necessarily relates the $U(1)$ coupling $g^{\prime}$ to the $SU(2)$ weak coupling $g$? It is shown in this manuscript that this can be accomplished by embedding $SU(2) \times U(1)$ into $SU(3)_W$ (The Weak Eightfold Way) with the following results: 1) The same prediction of the weak mixing angle is obtained; 2) The scalar representations of $SU(3)_W$ contain all those that are needed to build the the EW-$\nu_R$ model and, in particular, the real Higgs triplet used in the construction of the electroweak monopole. 3) Anomaly freedom requires the existence of mirror fermions present in the EW-$\nu_R$ model. 4) Vector-Like Quarks (VLQ) with unconventional electric charges are needed to complete the $SU(3)_W$ representations containing the right-handed up-quarks, with interesting experimental implications such as the prediction of doubly-charged hybrid mesons.
We explore features in the orientation of jet splitting products relative to the dijet production plane, with a focus on effects induced by “non-interfering” new physics operators in the standard model effective field theory (SMEFT). We construct an asymmetry variable by integrating the expected angular shape with the differential cross section. This search is sensitive to precisely one CP-conserving Wilson coefficient in the SMEFT, and it is also relatively unaffected by EFT interpretation/theory errors, making it nicely complementary to other searches. We consider competing contributions to the asymmetry from next-to-leading-order effects in QCD and showering of leading-order processes, and characterize signal visibility as a function of luminosity, scale, and systematic uncertainties.
https://pitt.zoom.us/j/92596581799
There is a guaranteed background of stochastic gravitational waves produced in the thermal plasma in the early universe. Its energy density per logarithmic frequency interval scales with the maximum temperature which the primordial plasma attained at the beginning of the standard hot big bang era. It peaks in the microwave range, at around $80$ GHz $[106.75/g_{*s}]^{1/3}$, where $g_{*s}$ is the effective number of entropy degrees of freedom in the primordial plasma at the maximum temperature. We present a state-of-the-art prediction of this Cosmic Gravitational Microwave Background (CGMB) for the case of the Standard Model (SM) as well as for several of its extensions. Furthermore, we discuss the current upper limits on the CGMB and the prospects to detect it in laboratory experiments and thus measure the maximum temperature and the effective number of degrees of freedom at the beginning of the hot big bang.
Computing sufficiently precise theoretical gravitational wave observables for realistic systems such as compact object binaries remains an essential and notoriously challenging task. In this talk, I will discuss a post-Newtonian effective field theory approach to this problem, focusing specifically on objects with spin. Using this framework, I will present new results at next-to-leading order and compare with those obtained using other formalisms for both spin-orbit and spin-spin contributions. In particular, we obtain the contribution of these effects to the orbital frequency and accumulated orbital phase as well as the adiabatic invariants and flux-balance laws. Importantly, this approach offers a straightforward path forward to systematically push the state-of-the-art to higher orders.
Abstract: During the inflation era, the properties (such as mass and interactions) of the fields coupled to the inflaton field may change substantially. As a result, drastic phenomena, such as first order phase transitions, may happen. In this talk, I will present simple models that first-order phase transition can happen and finish during inflation. I will discuss the properties of the gravitational wave (GW) signals produced by first-order phase transitions during inflation. I will show that there is a unique oscillatory feature in the GW spectrum. I will also show that we may be able to observe directly such a signal through future terrestrial or spatial GW detectors.
While Big Bang cosmology successfully explains much of the history of our universe, there are certain features it does not explain, for example the spatial flatness and uniformity of our universe. One widely studied explanation for these features is cosmological inflation. I will discuss the gravitational wave spectra generated by inflaton field configurations oscillating after inflation for E-Model, T-Model, and additional inflationary models. I will show that these gravitational wave spectra provide access to some inflation models beyond the reach of any planned cosmic microwave background (CMB) experiments, such as LiteBIRD, Simons Observatory, and CMB-S4. Specifically, while these experiments will be able to resolve a tensor-to-scalar ratio ($r$) down to $10^{-3}$, I show that gravitational wave background measurements have the potential to probe certain inflation models for $r$ values down to $10^{-14}$. Importantly, all the gravitational wave spectra from E- and T-model inflation lie in the MHz-GHz frequency range, motivating development of gravitational wave detectors in this range.
I introduce DarkFlux, a new tool for the analysis of indirect detection in general Dark Matter models. This tool can compute the flux spectrum for next generation models where Dark Matter annihilates to multiple sets of Standard Model particles. It computes and plots the annihilation ratios scanning over dark matter masses, computes and visualizes the total flux spectrum, and compares models to a set of experimental constraints setting a limit on DM mass for generic user generated models.
We will discuss gravitational wave signals sourced by hydrodynamic and hydromagnetic turbulent sources that might have been present in the early universe at epochs such as the quantum chromodynamic (QCD) phase transition. We consider various models of primordial turbulence: purely hydrodynamical turbulence induced by fluid motions, magnetohydrodynamic (MHD) turbulence dominated either by kinetic or magnetic energy both with and without helicity. We will also address the generation of circularly polarized gravitational waves by parity violating turbulent sources. We will present our results of numerical modeling of the early-universe turbulence and resulting gravitational waves and we will review the signal detection prospects. In particular, we will discuss the potential of explaining the recent observational evidence by NANOGrav collaboration for a stochastic gravitational wave background in the nanohertz frequency range through hydro and hydromagnetic turbulence at the QCD energy scale.
In this talk, I will present the recent result on gravitational waves from cosmological first-order phase transitions obtained using all currently available gravitational wave data from LIGO and Virgo's first three observing runs.
Gravitational waves have a periodic effect on the apparent positions of stars on the sky. This effect can be quantified and hence ultra-precise astrometric measurements (like the ones from Gaia) can provide a new method to search for gravitational signals. I will describe the principles which give rise to the astrometric signature of gravitational waves, and examine this result in the context of Einsteinian and alternative polarization states. I will discuss some of the data analysis challenges that will have to be overcome when trying to search for GWs in the extremely large (>$10^9$ stars) Gaia data set, and will present some preliminary estimates of the sensitivity that may be achievable. I will also describe the significance of astrometric measurements for probing stochastic GW backgrounds, and derive the relevant response correlation functions for all polarization modes. If time permits, I will also describe a novel method for constraining the speed of gravity by using astrometry. Throughout, I will keep a parallel between our work and analogous results from the PTA community.
This talk will discuss scenarios where dark matter abundance undergoes a "bounce" - a brief period of increase before thermal freezeout, following the standard exponential Boltzmann suppression - and its related phenomenological aspects.
We consider how a modified cosmological history with a period of electroweak confinement could allow a WIMP dark matter candidate to escape current exclusion bounds. We consider an $SU(2)_L$ vector doublet fermionic dark matter candidate which confines with standard model fermions during this era. These composite particles interact, depleting the dark matter abundance. After these processes freeze out, the electroweak period deconfines and proceeds according to the typical cosmological timeline. We find that this scenario naturally leads to a WIMP dark matter candidate while avoiding current exclusion bounds.
We present two distinct models which rely on 1st order phase transitions in a dark sector. The first is a minimal model for baryogenesis which employs a new dark SU(2) gauge group with two doublet Higgs bosons, two lepton doublets, and two singlets. The singlets act as a neutrino portal that transfers the generated baryon asymmetry to the Standard Model. The model predicts extra relativistic degrees of freedom, exotic decays of the Higgs and Z bosons, and stochastic gravitational waves detectable by future experiments.
The second model additionally produces (asymmetric) dark matter while the dark sector is expanded to an SU(3)xSU(2)xU(1) gauge group. Dark matter is comprised of dark neutrons or dark protons and pions.This model is highly discoverable at both dark matter direct detection and dark photon search experiments and the strong dark matter self interactions may ameliorate small-scale structure problems.
We present novel constraints on sub-GeV dark matter models involving a light particle $\chi$ and a $U(1)'$ dark photon mediator. Using measurements of $N_{\textrm{eff}}$ from the CMB and post-BBN abundances of deuterium and helium-4, we derive constraints on the mass $m_{\chi}$ of the dark matter particle, assuming an MeV-scale mediator mass. Depending on the model parameters, we find that values of $m_{\chi}$ below $\sim 8$-$10$ MeV produce a tension between the predicted values of these CMB and BBN parameters and their experimentally-determined values. We find that this constraint cannot be circumvented by simply adding additional degrees of freedom in the form of dark radiation. Finally, we compare these results to the sensitivities of existing and proposed direct detection experiments, and find an overlap between the regions of parameter space that many of these experiments will probe and the region of parameter space that is constrained by this analysis.
Non-trivial dynamics within the dark sector can give rise to a complicated, non-thermal dark-matter phase-space distribution, which in turn can have a significant impact on the growth of the cosmic structure. In this talk, we explore the cosmological implications of such non-trivial dark-sector dynamics. We show how the non-trivial features in the phase-space distribution can lead to modifications to quantities of structure formation such as the matter power spectrum and the halo mass function. We then examine the extent to which one can address the archaeological "inverse" problem of deciphering the properties of the underlying dark sector from the matter power spectrum. We present a simple one-line conjecture which can be used to “reconstruct” the dark-matter phase-space distribution directly from the shape of the matter power spectrum and show that salient features of the distribution can be successfully reproduced -- even for non-trivial distributions which are highly non-thermal and/or multi-modal. Our conjecture therefore provide an operational tool for probing the dark sector which does not rely on the existence of non-gravitational couplings between dark and visible states.
The distribution of primordial dark-matter velocities can significantly influence the growth of cosmological structure. In principle, one can therefore exploit the halo-mass distribution in order to learn about the dark sector. In practice, however, this task is both theoretically and computationally intractable. In this talk, we present a simple one-line conjecture which can be used to "reconstruct" the primordial dark-matter velocity distribution directly from the shape of the halo-mass function. Although our conjecture is completely heuristic, we show that it successfully reproduces the salient features of the underlying dark-matter velocity distribution --- even for non-trivial distributions which are highly non-thermal and/or multi-modal, such as might occur for non-minimal dark sectors. Our conjecture therefore provides an operational tool for probing the dark sector which does not rely on the existence of non-gravitational couplings between dark and visible states.
We study the phenomenon of gravitational particle production as applied to a scalar spectator field in the context of α-attractor inflation. Assuming that the scalar has a minimal coupling to gravity, we calculate the abundance of gravitationally-produced particles as a function of the spectator's mass $m_χ$ and the inflaton's α parameter. If the spectator is stable and sufficiently weakly coupled, such that it does not thermalize after reheating, then a population of spin-0 particles is predicted to survive in the universe today, providing a candidate for dark matter. Inhomogeneities in the spatial distribution of dark matter correspond to an isocurvature component, which can be probed by measurements of the cosmic microwave background anisotropies. We calculate the dark matter-photon isocurvature power spectrum and by comparing with upper limits from Planck, we infer constraints on $m_χ$ and α. If the scalar spectator makes up all of the dark matter today, then for α=10 and $T_{RH}=10^4 \mathrm{GeV}$ we obtain $m_χ>1.8×10^{13} \mathrm{GeV}≈1.2 m_ϕ$, where $m_ϕ$ is the inflaton's mass.
I will discuss the Higgs-portal dark matter scenario in the 5-dimensional brane world cosmology, such as Randall-Sundrum cosmology and Gauss-Bonnet cosmology.
The structures of Yukawa matrices have been a long-standing mystery of the Standard Model. One possible solution is assuming an abelian $U(1)_F$ flavor symmetry and introducing a small parameter $\epsilon$ through the Froggatt-Nielson mechanism. In this talk, I will show how to realize the Froggatt-Nielson mechanism within the framework of composite Higgs models. In this type of model, both the flavor structure and electroweak symmetry breaking originate from TeV-scale strong dynamics. The flavon field arises as a pseudo-Nambu-Goldstone bosons of the broken symmetry and the Froggatt-Nielson fields (vector-like fermions) arise as composite resonances (hadrons) of the strong dynamics.
The CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the CP-nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant CP-odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the tt̄H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.
The associated production of a $b\bar{b}$ pair with a Higgs boson could provide an important probe to both the size and the phase of the bottom-quark Yukawa coupling, $y_b$. However, the signal is shrouded by several irreducible background processes. We show that the analysis of kinematic shapes provides us with a concrete prescription for separating the $y_b$-sensitive production modes from both the irreducible and the QCD-QED backgrounds using the $b\bar{b}\gamma\gamma$ final state. We draw a page from game theory and use Shapley values to make Boosted Decision Trees interpretable in terms of kinematic measurables and provide physics insights into the variances in the kinematic shapes of the different channels that help us complete this feat. Adding interpretability to the machine learning algorithm opens up the black-box and allows us to cherry-pick only those kinematic variables that matter most in the analysis. We resurrect the hope of constraining the size and, possibly, the phase of $y_b$ using kinematic shape studies of $b\bar{b}h$ production with the full HL-LHC data and at FCC-hh.
Probing the charm Yukawa coupling is very important to confirm Higgs-fermion interactions and search for deviations from the Standard Model (SM), yet extremely challenging due to enormous QCD background. In this study, we examine the sensitivity of probing Higgs-charm coupling at Large Hadron Collider (LHC) via vector boson fusion with a photon radiation. This additional photon provides an extra handle in triggering and helps suppress gluon-rich background. With a proposed trigger strategy and utilizing multivariate analysis, we find a projected sensitivity of about 5 times the SM charm Yukawa coupling at 95% C.L. at High Luminosity LHC (HL-LHC). Our result is comparable and complementary to existing projections at HL-LHC.
We propose soft breaking mechanism for dark matter (DM) shift symmetry in a class of composite dark matter models, where both DM and the Higgs boson arise as pseudo Nambu-Goldstone bosons from novel strong dynamics. Our mechanism is utilized to suppress the non-derivative portal coupling between the Higgs boson and DM particle, which can evade the stringent bound of current DM direct detection experiments. Otherwise this non-derivative portal coupling would naturally be at the same order of the Higgs quartic, rendering this class of models under severe crisis. For realizing soft breaking mechanism, we introduce vector-like top partners, dubbed as "softons", to restore the shift symmetry of DM in top Yukawa sector, which however is only broken by the softon masses. The portal coupling would automatically vanish as the shift-symmetry-breaking softon masses approach zero. Specifically we present a proof-of-concept model of soft breaking, based on the coset O(6)/O(5) and the simplest fermion embedding, and study its DM phenomenology, where we show a large amount of novel parameter space is opened up by using the soft breaking mechanism.
Testing the Yukawa couplings of the Higgs boson to quarks and leptons is important to understand the origin of fermion masses. The talk presents cross section measurements in Higgs boson decays to two bottom quarks or two tau leptons, searches for Higgs boson decays to two charm quarks or two muons, as well as indirect constraints of the charm-Yukawa coupling. The production of Higgs bosons in association with top quarks will also be discussed. These analyses are based on pp collision data collected at 13 TeV.
In this talk, top quark pair production is proposed as a probe of the CP structure of the top quark Yukawa interaction. Since the top-Higgs coupling enters through Higgs boson loops, a next-to-leading-order calculation is performed in the Standard Model Effective Field Theory in order to include arbitrary CP mixtures. This approach of analyzing Higgs boson degrees of freedom in loops benefits from the large top quark pair production rate and the excellent perturbative control over the theoretical prediction. The resulting sensitivity is contrasted with direct probes with on-shell Higgs boson production in association with a single top quark or top quark pair. Thereby, loop sensitivity is established as a complementary handle to on-shell sensitivity over a wide range of parameter space.
Since the discovery of the Higgs boson in 2012, one of the main efforts of the LHC experiments has been to characterize the new particle precisely. This includes measurement of mass, spin properties and couplings as well as differential properties. This talk will emphasize most of the important Higgs analyses decaying to various final states carried by the CMS experiment in recent times.
Searches for heavy neutral lepton production in K+ → e+N and K+ → +N decays using the data set collected by the NA62 experiment at CERN in 2016-18 are presented. Upper limits on the elements of the extended neutrino mixing matrix |Ue4|2 and |U4|2 are established at the levels of 10-9 and 10-8, respectively, improving on the earlier searches for heavy neutral lepton production and decays in the kinematically accessible mass range.
The Majorana nature of neutrinos and whether lepton number symmetry is conserved are among the most pressing mysteries in physics today. This follows from their widespread implications for cosmology, nuclear physics, and particle physics. Along these lines, searches for the neutrinoless $\beta\beta$ ($0\nu\beta\beta$) decay mode of heavy nuclei are highly sensitive probes of these questions, albeit with important limitations. In this talk we present a new look into the high-energy realization of the $0\nu\beta\beta$ process at the Large Hadron Collider (LHC). As a case study, we focus on the same-sign WW scattering process $W^\pm W^\pm \to \mu^\pm \mu^\pm$, which violates lepton number and is outside the reach of nuclear decay experiments. Whether mediated by heavy Majorana neutrinos or more generally by the Weinberg operator, we find that the LHC offers incredible complementarity to lower energy experiments and further extends the sensitivity to the nature of neutrinos.
Companion papers:
- https://arxiv.org/abs/2011.02547
- https://arxiv.org/abs/2012.09882
If a heavy neutrino is discovered, determining its nature, i.e., whether it is a Dirac or a Majorana fermion, will be at the top of the list of the next questions to ask. A natural way to determine this is to analyze the particle's decays and to observe whether they violate lepton number. However, if the final state includes any light neutrinos, this is impossible. In that event, we may still be able to determine the nature by measuring the distribution of decay events. I will show how this procedure may be performed in the context of three-body decays of heavy neutrinos into a light neutrino and a pair of charged leptons.
Neutrinos are probably the most mysterious particles of the Standard Model. The mass hierarchy and oscillations, as well as the nature of their antiparticles, are currently being studied in experiments around the world. Moreover, in many models of the New Physics, baryon asymmetry or dark matter density in the universe are explained by introducing new species of neutrinos. Among others, heavy neutrinos of the Dirac or Majorana nature were proposed to solve problems persistent in the Standard Model. Such neutrinos with masses above the EW scale could be produced at future linear e+e- colliders, like the Compact LInear Collider (CLIC) or the International Linear Collider (ILC).
We studied the possibility of observing production and decays of heavy neutrinos in qql final state at the ILC running at 500 GeV and 1 TeV and the CLIC running at 3 TeV. The analysis is based on the WHIZARD event generation and fast simulation of the detector response with DELPHES. Dirac and Majorana neutrinos with masses from 200 GeV to 3.2 TeV are considered. Estimated limits on the production cross sections and on the neutrino-lepton coupling are compared with the current limits coming from the LHC running at 13 TeV, as well as the expected future limits from hadron colliders. Impact of the gamma-induced backgrounds on the experimental sensitivity is also discussed. Obtained results are stricter than other limit estimates published so far.
We examine the detection prospects for a long-lived biνo, a pseudo-Dirac bino which is responsible for neutrino masses, at the LHC and at dedicated long-lived particle detectors. The biνo arises in U(1)_R-symmetric supersymmetric models where the neutrino masses are generated through higher dimensional operators in an inverse seesaw mechanism. At the LHC the biνo is produced through squark decays and it subsequently decays to quarks, charged leptons and missing energy via its mixing with the Standard Model neutrinos. We consider long-lived biνos which escape the ATLAS or CMS detectors as missing energy and decay to charged leptons inside the proposed long-lived particle detectors FASER, CODEX-b, and MATHUSLA. We find the currently allowed region in the squark-biνo mass parameter space by recasting most recent LHC searches for jets+MET.We also determine the reach of MATHUSLA, CODEX-b and FASER. We find that a large region of parameter space involving squark masses, biνo mass and the messenger scale can be probed with MATHUSLA, ranging from biνo masses of 10 GeV-2 TeV and messenger scales 10^2−10^11TeV for a range of squark masses.
Heavy neutral leptons (HNLs) are among the simplest and most natural extensions of the Standard Model; they are widely expected in a range of more complicated dark sector models. At MeV scale masses, HNLs are typically very long lived and can be difficult to search for with laboratory experiments. In this talk I will discus how large volume detectors can search for decaying HNLs produced by neutrinos scattering against terrestrial material (i.e. the entire volume of the Earth). This represents an exciting new detection strategy that can already place new constraints on $\nu_\tau-N$ mass mixing and constraints on dipole portal couplings to all flavors of neutrinos.
We propose a supersymmetric extension of the minimal $U(1)_X$ model, along with a new $Z_2$-parity. One of the salient features of this model relates to how the $U(1)_X$ gauge symmetry is broken at the TeV scale. The running of the Majorana coupling of the $Z_2$-even right handed neutrino is shown to become large due to radiative corrections. As a result, this running causes the mass squared of the corresponding right handed sneutrino to negative values and is ultimately responsible for breaking the gauge symmetry. By assigning one right-handed neutrino $Z_2$-odd parity, it can remain a viable dark matter (DM) candidate, despite R-parity being broken. Furthermore, the DM relic abundance receives an enhanced annihilation cross section due to the $U(1)_X$ gauge boson ($Z'$) resonance and is in agreement with the current observations. We have found a complementarity that exists between the observed DM relic abundance and search results for the $Z^\prime$ boson resonance at the Large Hadron Collider that further constrains the parameter space of our $U(1)_X$ model.
We study the phenomenology of the minimal $(2,2)$ inverse-seesaw model supplemented with Abelian flavour symmetries. To ensure maximal predictability, we establish the most restrictive flavour patterns which can be realised by those symmetries. This setup requires adding an extra scalar doublet and two complex scalar singlets to the Standard Model, paving the way to implement spontaneous CP violation. It is shown that such CP-violating effects can be successfully communicated to the lepton sector through couplings of the scalar singlets to the new sterile fermions. The Majorana and Dirac CP phases turn out to be related, and the active-sterile neutrino mixing is determined by the active neutrino masses, mixing angles and CP phases. We investigate the constraints imposed on the model by the current experimental limits on lepton flavour-violating decays, especially those on the branching ratio $\text{BR}(\mu\rightarrow e \gamma)$ and the capture rate $\text{CR}(\mu-e,{\rm Au})$. The prospects to further test the framework put forward in this work are also discussed in view of the projected sensitivities of future experimental searches sensitive to the presence of heavy sterile neutrinos. Namely, we investigate at which extent upcoming searches for $\mu\rightarrow e \gamma$, $\mu \rightarrow 3e$ and $\mu-e$ conversion in nuclei will be able to test our model, and how complementary will future high-energy collider and beam-dump experiments be in that task.
We study a challenging signature in collider physics, that the final state contains soft and displaced tracks, with the help of the CMS Open Data. This signature is of particular interest since it corresponds to a well-motivated dark matter coannihilation regime. We propose to search for signals in monojet plus missing energy events, exploiting displaced vertices reconstructed from soft tracks. We perform such a search in the 8 TeV CMS Open Data events with a luminosity of 11.6 fb$^{-1}$ and obtain 95\% confidence level limit on the plane of top squark mass $m_{\tilde t}$ and lightest neutralino mass $m_{\chi^0}$. In the region $m_{\tilde t} - m_{\chi^0} \approx 15-30$ GeV, we exclude $m_{\tilde t} < 350$ GeV, which is more stringent than the ATLAS and CMS results using 8 TeV data with about 20 fb$^{-1}$ luminosity. Our study shows that the CMS Open Data can be a powerful tool to help theorists study efficiencies and backgrounds of non-conventional new physics searches.
Higgsinos are a particularly compelling form of dark matter, and are on the verge of detection by multiple current experimental avenues. They can arise in models with decoupled scalars that enjoy the benefits of depending on very few parameters while still explaining gauge coupling unification, dark matter, and most of the hierarchy between the Planck and electroweak scales, and they remain undetected to past experiments. My talk will cover the reach for current and upcoming electron electric dipole moment experiments to observe higgsino dark matter models.
A scan of soft SUSY breaking parameters within the string theory landscape with the MSSM assumed as the low energy effective field theory– using a power-law draw to large soft terms coupled with an anthropic selection of a derived weak scale to be within a factor four of our measured value– predicts a peak probability of $m_h \simeq 125 \text{ GeV}$ with sparticles masses typically beyond the reach of LHC Run 2. Such multiverse simulations usually assume a fixed value of the SUSY conserving superpotential $\mu$ parameter to be within the assumed anthropic range, $\mu < \sim 350 \text{ GeV}$. However, depending on the assumed solution to the SUSY $\mu$ problem, the expected $\mu$ term distribution can actually be derived. We examine two solutions to the SUSY $\mu$ problem. The first is the gravity-safe Peccei-Quinn (GSPQ) model based on an assumed $\mathbb{Z}_{24}^R$ discrete $R$-symmetry which allows a gravity-safe accidental, approximate Peccei-Quinn global symmetry to emerge which also solves the strong CP problem. The second case is the Giudice-Masiero solution wherein the $\mu$ term effectively acts as a soft term and has a linear draw to large values. For the first case, we also present the expected landscape distribution for the PQ scale $f_a$; in this case, weak scale anthropics limits its range to the cosmological sweet zone of around $f_a ∼ 10^{11} \text{ GeV}$.
Clockwork models can explain the flavor hierarchies in the Standard Model quark and lepton spectrum.
We construct supersymmetric versions of such flavor clockwork models. The zero modes of the clockwork are identified with the fermions and sfermions of the Minimal Supersymmetric Standard Model. In addition to generating a hierarchical fermion spectrum, the clockwork also predicts a specific flavor structure for the soft SUSY breaking sfermion masses. We find sizeable flavor mixing among first and second generation quarks. Constraints from Kaon oscillations require the masses of either squarks or gluinos to be above a scale of $\sim 3$ PeV.
Supersymmetry (SUSY) provides elegant solutions to several problems in the Standard Model, and searches for SUSY particles are an important component of the LHC physics program. Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the gluons and third generation quarks with masses light enough to be produced at the LHC. This talk will present the latest results of searches conducted by the ATLAS experiment which target gluino and squark production, including stop and sbottom, in a variety of decay modes. It covers both R-parity conserving models that predict dark matter candidates and R-parity violating models that typically lead to high-multiplicity final states without large missing transverse momentum.
The latest results from searches for third generation supersymmetric particles with the CMS experiment will be presented. The analyses are based on the full dataset of pp collisions recorded at sqrt(s) = 13 TeV during the LHC Run 2.
The direct production of electroweak SUSY particles, including sleptons, charginos, and neutralinos, is a particularly interesting area with connections to dark matter and the naturalness of the Higgs mass. The small production cross sections lead to difficult searches, despite relatively clean final states. This talk will highlight the most recent results of searches performed by the ATLAS experiment for supersymmetric particles produced via electroweak processes, including analyses targeting small mass splittings between SUSY particles. Models are targeted in both R-parity conserving as well as R-parity violating scenarios.
In the Standard Model, CP violation in the Electroweak sector is parametrized by the Jarlskog Invariant. This is the flavor invariant sensitive to CP violation with the least number of Yukawa matrices that can be built. When higher dimensional operators are allowed, and the Standard Model Effective Field Theory is constructed, numerous new sources for CP violation can appear. However, the description of CP violation as a collective effect, present in the SM, is inherited by its Effective extension. Here, I will discuss how such a behaviour can be consistently captured, at dimension 6, by flavor invariant, CP violating objects, linear in the Wilson coefficients. Such a description ensures that CP violation in the SMEFT is treated in a basis independent manner. In particular, I claim these are the objects that have to vanish, together with the SM Jarlskog Invariant, for CP to be conserved, and viceversa. The scaling properties of these invariants demonstrates that, while CP is not an accidental symmetry of the Standard Model, its breaking is accidentally small at the renormalizable level. Implications for specific flavor models, such as MFV, will be addressed.
https://pitt.zoom.us/j/93951025550
https://pitt.zoom.us/j/93951025550
The THDMa is a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet and allows for mixing between all possible scalar states. In the gauge eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a priori any dark matter spins states. The option where dark matter is fermionic is currently one of the standard benchmarks for the experimental collaborations, and several searches at the LHC constrain the corresponding parameter space. However, most current studies constrain regions in parameter space by setting all but 2 of the 12 free parameters to fixed values. I discuss a generic scan on this model, allowing all parameters to float. All current theoretical and experimental constraints are taken into account, including bounds from current searches, recent results from B-physics, as well as bounds from astroparticle physics. We identify regions in the parameter space which are still allowed after these have been applied and which might be interesting for an investigation at current and future collider machines.
The general $U(1)_𝑋$ extension of the Standard Model (SM) is a well motivated scenario which has a plenty of new physics options. Such a model is anomaly free which requires to add three generations of the SM singlet right-handed neutrinos (RHNs) which naturally generates the light neutrino masses by the seesaw mechanism.This offers interesting phenomenological aspects in the model. In addition to that the model is equipped with a beyond the SM (BSM) neutral gauge boson, $𝑍^\prime$ which interacts with the SM and BSM particles showing a variety of new physics driven signatures. After the anomaly cancellation the $U(1)_𝑋$ charge of the particles are expressed in terms of the SM Higgs doublet and the SM Higgs singlet which allows us to study the interaction of the fermions with the $𝑍^\prime$.In this paper we investigate the pair production mechanism of the different charged through the photon, $𝑍$ and $𝑍^\prime$ boson exchange processes at the electron-positron $(𝑒^-𝑒^+)$.The angular distributions, forward-backward $(\mathcal{A}_{FB})$, left-right $(\mathcal{A}_{LR})$ and left-right forward-backward $(\mathcal{A}_{LR,FB})$ asymmetries of the different charged fermion pair productions show substantial deviation from the SM results.
Based on a number of features from proton-proton collisions taken during Run 1 data taking period at the LHC, a boson with a mass around the Electro-Weak scale was postulated such that a significant fraction of its decays would comprise the Standard Model (SM) Higgs boson and an additional scalar, S. One of the implications of a simplified model, where S is treated a SM Higgs boson, is the anomalous production of high transverse momentum leptons. Corners of the phase-space are fixed according to the model parameters derived in 2017 without additional tuning, in order to nullify potential look-else-where effects or selection biases. A combined study of subsequent data is indicative of significant discrepancies between the data and SM Monte Carlos in a variety of final states involving multiple leptons with and without b-quarks. These discrepancies appear in corners of the phase-space where different SM processes dominate, indicating that the potential mismodeling of a particular SM process is unlikely to explain them. The internal consistency of these anomalies and their interpretation in the framework of the original hypothesis is quantified. Implications on the Higgs boson measurements, muon g-2 and and astrophysics are also discussed.
In this work (arXiv: https://arxiv.org/abs/1810.11420, DOI: 10.1140/epjc/s10052-020-7822-0) a new physics scenario shows that four-fermion operators of Nambu-Jona-Lasinio (NJL) type have a strong-coupling UV fixed point, where composite fermions F (bosons Π) form as bound states of three (two) SM elementary fermions and they couple to their constituents via effective contact interactions at the composite scale Λ≈O(TeV). We present a phenomenological study to investigate such composite particles at the LHC by computing the production cross sections and decay widths of composite fermions in the context of the relevant experiments at the LHC with pp collisions at √s=13 TeV and √s=14 TeV. Systematically examining all the different composite particles F and the signatures with which they can manifest, we found a vast spectrum of composite particles F that has not yet been explored at the LHC. Recasting the recent CMS results of the resonant channel pp→e+F→e+e−qq¯′, we find that the composite fermion mass mF below 4.25 TeV is excluded for Λ/mF = 1. We further highlight the region of parameter space where this specific composite particle F can appear using 3 ab−1, expected by the High-Luminosity LHC, computing 3 and 5 σ contour plots of its statistical significance.
We discuss the physics potential of a multi-TeV muon collider. We present the results for the main SM processes together with popular BSM models, emphasizing the annihilation and VBF regime at very-high energies. We also discuss some preliminary results about the Effective Vector Boson Approximation and its implementation in MadGraph5_aMC@NLO.
A high energy muon collider can provide new and complementary discovery potential to the LHC or future hadron colliders. Leptoquarks are a motivated class of exotic new physics models, with distinct production channels at hadron and lepton machines. We study a vector leptoquark model at a muon collider with $\sqrt{s}$=3,14 TeV within a set of both UV and phenomenologically motivated flavor scenarios. We compute which production mechanism has the greatest reach for various values of the leptoquark mass and the coupling between leptoquark and Standard Model fermions. We find that we can probe leptoquark masses up to an order of magnitude beyond s√ with perturbative couplings. Additionally, we can also probe regions of parameter space unavailable to flavor experiments. In particular, all of the parameter space of interest to explain recent low-energy anomalies in B meson decays would be covered even by a $\sqrt{s}$=3 TeV collider.
Because of its ability to systematically capture beyond Standard Model (SM) effects, effective field theory (EFT) has received much attention in phenomenological analyses of e.g. LHC data. Recent theoretical studies have focused on operator basis construction and loop level calculations in EFTs. In this work, we construct the complete basis for scalar $\phi^4$ EFT up to mass dimension 12, with the help of the Hilbert series method. We present high loop calculations (up to 5 loop), and find unexpected zeros and interesting symmetric structures in the anomalous dimension matrix. The method we use can be extended to more general theories, i.e. SMEFT and be applied in high precision measurements within the SMEFT framework at the LHC.
The lack of evidence of New Physics coming from direct searches of resonances at the LHC calls for an increase in efforts to devise new observables that can indirectly probe New Physics. Additionally, the future FCC-hh will make available new processes, inaccessible so far due to their low number of events. Studying the high transverse momentum distribution of diboson production processes at FCC-hh is then an interesting path to explore. I will discuss how the diboson processes Wh and Zh, with leptonic decays for W and Z and the Higgs decaying to 2 photons, will allow us to know more about the physics of the Higgs boson in an EFT framework. I will also focus on how doubly differential distributions give us access to higher-dimension operators that, otherwise, would require more specific observables. Finally, I will show how these processes will help to improve the bounds on aTGCs obtained from electron-positron colliders.
https://pitt.zoom.us/j/93567042779
In the early universe, black holes can easily produce monopoles. Via Hawking radiation, evaporating black holes heat up the surrounding plasma and create a temperature profile around the black hole that features symmetry restoration near the center. Eventually, this region cools off and undergoes the Kibble mechansim, producing monopoles. We demonstrate that this process can very efficiently produce monopoles. In the case where black holes reheat the universe, reheat temperatures above 100 GeV can already lead to monopoles overclosing the universe.
Primordial black holes (PBHs) lighter than $5\times 10^{14}\,$g cannot constitude the dark matter (DM) because they are already evaporated, but they are constrained by early universe phenomena (BBN, CMB). PBHs lighter than $10^9\,$g, however, are at present mostly unconstrained. In this talk, we will present scenarios where light (spinning) PBHs with $M_\text{PBH}<10^9\,$g evaporate in the early universe before BBN and produce either a warm DM particle or dark radiation. We will then confront the predictions on respectively structure formation and $\Delta N_\text{eff}$ to observations to conclude with Hawking radiation constraints on these light PBHs.
We present precision calculations of dark radiation in the form of gravitons coming from Hawking evaporation of spinning primordial black holes (PBHs) in the early Universe. Our calculation incorporates a careful treatment of extended spin distributions of a population of PBHs, the PBH reheating temperature, and the number of relativistic degrees of freedom. We compare our precision results with those existing in the literature, and show constraints on PBHs from current bounds on dark radiation from BBN and the CMB, as well as the projected sensitivity of CMB Stage 4 experiments.As an application, we consider the case of PBHs formed during an early matter-dominated era (EMDE). We calculate graviton production from various PBH spin distributions pertinent to EMDEs, and find that PBHs in the entire mass range up to $10^9\,$g will be constrained by measurements from CMB Stage 4 experiments, assuming PBHs come to dominate the Universe prior to Hawking evaporation. We also find that for PBHs with monochromatic spins $a^*>0.81$, all PBH masses in the range $10^{-1}\,{\rm g} < M_{\rm BH} <10^9\,{\rm g}$ will be probed by CMB Stage 4 experiments.
Primordial black holes (PBHs) can form as a result of primordial scalar perturbations at small scales. This PBH formation scenario has associated gravitational wave (GW) signatures from second-order GWs induced by the primordial curvature perturbation, and from second-order GWs produced by the gravitational potential of the PBHs themselves. We investigate the ability of next generation GW experiments, including BBO, LISA, and CE, to probe this PBH formation scenario in a wide mass range ($10 - 10^{27}$g). Measuring the stochastic GW background with GW observatories can constrain the allowed parameter space of PBHs including a previously unconstrained region where light PBHs ($<10^9$g) temporarily dominate the energy density of the universe before evaporating. We also show how PBH formation impacts the reach of GW observatories to the primordial power spectrum and provide constraints implied by existing PBH bounds.
According to our current models of stellar collapse, stars in the mass range ~64-135 M⊙ undergo pair-instability supernovae, leaving behind no remnant. However, in 2019 LIGO and Virgo detected a black hole merger event with a high probability that the mass of the heavier black hole was within this pair-instability mass gap, motivating the exploration of novel black hole formation mechanisms. We hypothesize that clumps of gas in an atomic dark sector could cool efficiently enough to form a black hole within the mass gap. As a first step, we investigate this scenario with Standard Model parameters by simulating a star without nuclear reactions using the MESA stellar evolution code. Generalizing this investigation to the dark QED sector, we expand the parameter space using a combination of analytical and numerical methods.
Magnetically charged black holes (MBHs) are interesting solutions of the Standard Model and general relativity. They may possess a “hairy” electroweak-symmetric corona outside the event horizon, which speeds up their Hawking radiation and leads them to become nearly extremal on short timescales. Their masses could range from the Planck scale up to the Earth mass. We study various methods to search for primordially produced MBHs and estimate the upper limits on their abundance. We revisit the Parker bound on magnetic monopoles and show that it can be extended by several orders of magnitude using the large-scale coherent magnetic fields in Andromeda. This sets a mass-independent constraint that MBHs have an abundance less than $4 × 10^{−4}$ times that of dark matter. MBHs can also be captured in astrophysical systems like the Sun, the Earth, or neutron stars. There, they can become non-extremal either from merging with an oppositely charged MBH or absorbing nucleons. The resulting Hawking radiation can be detected as neutrinos, photons, or heat. High-energy neutrino searches in particular can set a stronger bound than the Parker bound for some MBH masses, down to an abundance $10^{−7}$ of dark matter.
Recent works have revealed that the fine-grained entropy of a non-gravitating subsystem, when entangled with a gravitating region, can receive contributions from so-called quantum extremal islands. Applied to black holes, this reproduces the unitary Page curve for Hawking radiation. In this talk, I will show how these results can be applied to the thermal radiation measured by a static observer in de Sitter space. Focusing on JT gravity, I will emphasize the necessity of going beyond the thermal equilibrium of the Bunch-Davies state. We will see that a quantum extremal island can contribute to the fine-grained entropy, suggesting unitarity of the radiation, but this comes at a price: when the island appears a singularity forms that a static observer will eventually hit.
Perturbation theory for gravitating quantum systems tends to fail at very late times (a type of perturbative breakdown known as secular growth). We argue that gravity is best treated as a medium/environment in such situations, where reliable late-time predictions can be made using tools borrowed from quantum optics. To show how this works, we study the explicit example of a qubit hovering just outside the event horizon of a Schwarzschild black hole (coupled to a real scalar field) and reliably extract the late-time behaviour for the qubit state. At very late times, the so-called Unruh-DeWitt detector is shown to asymptote to a thermal state at the Hawking temperature.
We consider searches for the inelastic scattering of low-mass dark matter against nuclei at direct detection experiments, using the Migdal effect. We find that there are degeneracies between the dark matter mass and the mass splitting that are difficult to break. Using XENON1T data we set bounds on a previously unexplored region of the inelastic dark matter parameter space. For the case of exothermic scattering, we find that the Migdal effect allows xenon-based detectors to have sensitivity to dark matter with ${\cal O}({\rm MeV})$ mass, far beyond what can be obtained with nuclear recoils.
Aromatic organic compounds, because of their small excitation energies $\sim \mathcal O$(few eV) and scintillating properties, are promising targets for detecting dark matter of mass $\sim \mathcal O$(few MeV). Additionally, their planar molecular structures lead to large anisotropies in the electronic wavefunctions, yielding a significant daily modulation in the event rate expected to be observed in crystals of these molecules. We characterize the daily modulation rate of dark matter interacting with an anisotropic scintillating organic crystal such as trans-stilbene, and show that daily modulation is an $\sim \mathcal O$(1) fraction of the total rate for small DM masses and comparable to, or larger than, the $\sim 10\%$ annual modulation fraction at large DM masses. As we discuss in detail, this modulation provides significant leverage for detecting or excluding dark matter scattering, even in the presence of a non-negligible background rate. Assuming a non-modulating background rate of 1/min/kg that scales with total exposure, we find that a 100${\rm kg \cdot yr}$ experiment is sensitive to the cross section corresponding to the correct relic density for dark matter masses between $1.3-14\;\rm{MeV}$ ($1.5-1000\;\rm{MeV}$) if dark matter interacts via a heavy (light) mediator. This modulation can be understood using an effective velocity scale $v^* = \Delta E/q^*$, where $\Delta E$ is the electronic transition energy and $q^*$ is a characteristic momentum scale of the electronic orbitals. We also characterize promising future directions for development of scintillating organic crystals as dark matter detectors.
We point out several unexplored low-energy backgrounds to sub-GeV dark matter searches, which arise from high-energy particles of cosmic or radioactive origin that interact with detector materials. In this talk, I will focus on Cherenkov radiation and luminescence from electron-hole pair recombination. I will show that these processes provide plausible explanations of the observed events at SENSEI and SuperCDMS HVeV. A detailed simulation of these events at SENSEI will be presented in the companion talk. We also propose several important design strategies to mitigate such backgrounds, which could have a significant impact on the design of future dark matter experiments.
Several low-threshold detectors looking for sub-GeV dark matter have observed a large rate of low-energy events. The SENSEI experiment, which looks for small ionization signals in Silicon Skipper CCD to search for sub-GeV dark matter, has also observed a large single-electron event rate which cannot be explained by previously explored backgrounds. In this talk, I will focus on radiative backgrounds like Cherenkov radiation and Luminescence from electron-hole recombination in the SENSEI detector. With results from a detailed simulation of these backgrounds, I will show that a significant fraction of the observed single-electron rate can be attributed to these radiative processes.
The detection of low mass dark matter is under development with the advancement of experiment techniques. The superfluid helium-4 detector covers an extensive detection range from DM mass keV to GeV among the setups. I will present a complete theoretical framework for all processes within the superfluid to fill in the missing theory for sub-GeV DM detection. First, we use effective field theories to construct the interaction Lagrangian between quasi-particles. Second, we use a U(1) gauge spontaneous breaking and current element method to derive the interaction between test particles and quasi-particles. In the end, I will discuss relevant cross-sections and decay rates.
Large panels of etched plastic, situated aboard the Skylab Space Station and inside the Ohya quarry near Tokyo, have been used to set limits on fluxes of cosmogenic particles. These plastic particle track detectors also provide the best sensitivity for some heavy dark matter that interacts strongly with nuclei. We revisit prior dark matter bounds from Skylab, and incorporate geometry-dependent thresholds, a halo velocity distribution, and a complete accounting of observed through-going particle fluxes. These considerations reduce the Skylab bound's mass range by a few orders of magnitude. However, a new analysis of Ohya data covers a portion of the prior Skylab bound, and excludes dark matter masses up to the Planck mass. Prospects for future etched plastic dark matter searches are discussed.
We propose a self-interacting inelastic dark matter (DM) scenario as a possible origin of the recently reported excess of electron recoil events by the XENON1T experiment. Two quasi-degenerate Majorana fermion DM interact within themselves via a light hidden sector massive gauge boson and with the standard model particles via gauge kinetic mixing. We also consider an additional long-lived singlet scalar which helps in realising correct dark matter relic abundance via a hybrid setup comprising of both freeze-in and freeze-out mechanisms. While being consistent with the required DM phenomenology along with sufficient self-interactions to address the small scale issues of cold dark matter, the model with GeV scale DM can explain the XENON1T excess via inelastic down scattering of heavier DM component into the lighter one. All these requirements leave a very tiny parameter space keeping the model very predictive for near future experiments.
Motivated by the growing evidence for lepton flavour universality violation after the first results from Fermilab's muon $(g-2)$ measurement, we revisit one of the most widely studied anomaly free extensions of the standard model namely, gauged $L_{\mu}-L_{\tau}$ model, known to be providing a natural explanation for muon $(g-2)$. We also incorporate the presence of dark matter (DM) in this model in order to explain the recently reported electron recoil excess by the XENON1T collaboration. We show that the same neutral gauge boson responsible for generating the required muon $(g-2)$ can also mediate interactions between electron and dark matter. We consider two scenarios to explain the XENON1T excess; one with dark fermions boosted by DM annihilation and the other with inelastic down scattering of DM. In the former case, the required DM annihilation rate into dark fermion require a hybrid setup of thermal and non-thermal mechanisms to generate DM relic density. In the later case, a Dirac fermion DM, naturally stabilised due to its chosen gauge charge, is split into two pseudo-Dirac mass eigenstates due to Majorana mass term induced by singlet scalar which also takes part in generating right handed neutrino masses responsible for type I seesaw origin of light neutrino masses. The inelastic down scattering of heavier DM component can give rise to the XENON1T excess for keV scale mass splitting with lighter DM component. We fit our model with XENON1T data for both the cases and also find the final parameter space by using bounds from $(g-2)_{\mu}$, DM relic, lifetime of heavier DM, DM-electron scattering rate, neutrino trident production rate as well as other flavour physics, astrophysical and cosmological observations. The tightly constrained parameter space from all requirements remain sensitive to ongoing and near future experiments, keeping the scenario very predictive.