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The 2018 Phenomenology Symposium will be held May 7-9, 2018 at the University of Pittsburgh. It will cover the latest topics in particle phenomenology and theory plus related issues in astrophysics and cosmology.
Early registration will end April 16, 2018
Registration will close April 30, 2018
Talk submission will end April 23, 2018
Conference banquet May 8, 2018
Plenary program and full program are now available.
Confirmed plenary speakers and topics:
Parallel session mini-reviews:
Forum on early career development. Panelists: Sally Dawson, Keith Dienes
May 7, 1:00-1:45 PM
PITT PACC Travel Awards: With support from the NSF and DOE, there are a number of awards (up to $300 each) available to domestic graduate students for travel and accommodation to Pheno 18. A student applicant should send an updated CV and a statement of financial need, and arrange for a short recommendation letter sent from their thesis advisor, by email to pittpacc@pitt.edu with the subject line "Pheno 18 travel assistance". The decision will be based on the academic qualification, the talk submission to Pheno 18, and the financial need. The deadline for the application is April 9, and the winners will be notified by April 17. (Each research group may be limited to one awardee. Winners in the previous years may have lower priority for consideration. Winner institutes and names will be announced at the Symposium banquet.)
PHENO 2018 ORGANIZERS: Brian Batell, Cindy Cercone, Ayres Freitas, Dorival Gonçalves, Tao Han (chair), Ahmed Ismail, Adam Leibovich, Natália Maia, David McKeen, and Satyanarayan Mukhopadhyay
PHENO 2018 PROGRAM ADVISORS: Vernon Barger, Lisa Everett, Kaoru Hagiwara, JoAnne Hewett, Arthur Kosowsky, Yao-Yuan Mao, Tilman Plehn, Xerxes Tata, Andrew Zentner, and Dieter Zeppenfeld.
LOCAL EVENTS
The Pittsburgh Marathon will take place May 6, 2018
We study the impact of anomalous gauge boson and fermion couplings on the production of W+W− pairs at the LHC. Although constrained to be very small by LEP, anomalous fermion-gauge boson couplings can have important effects in LHC fits to anomalous couplings. Addtionally, we show that the QCD corrections have important effects, in particular when one W boson is longitudinally polarized and the other is transversely polarized. In effective field theory language, we demonstrate that the dimension-6 approximation to constraining new physics effects in W+W− pair production fails at pT∼500−1000 GeV.
Precision measurement at the LHC can provide probes of new physics which are com- plementary to direct searches. The high energy distribution of di-boson is a promising place, with the possibility of significant improvement with the accumulation of data. We focus on the semi-lepton final states, and make projections of the reach for future runs of the LHC with integrated luminosities of 300 fb−1 and 3 ab−1. We emphasize the im- portance of tagging the polarization of the vector bosons in particular for the WW and WZ channels. In particular, we employed a combination of kinematical distributions of both the W and Z, and their decay product to select the longitudinally polarized W and Z. We have also included our projections for the reach of the associated vector boson and Higgs production channel. We demonstrate that di-boson measurement in the semi- leptonic channel can surpass the sensitivity of the precision measurement at LEP, and they can be significantly more sensitive than the h -> Zγ measurements.
A summary of searches for heavy resonances with masses exceeding 1 TeV decaying into dibosons is presented, performed on data produced by LHC pp collisions at $\sqrt{s}$ = 13 TeV and collected with the CMS detector during 2016 and 2017. The 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 the Warped Extra Dimension and Heavy Vector Triplet theoretical models, two possible scenarios beyond the standard model.
We demonstrate the use of the Matrix Element Method (MEM) for the measurement of masses,
widths, and couplings in the case of single or pair-production of semi-invisibly decaying resonances.
For definiteness, we consider the two-body decay of a generic resonance to a visible particle from
the Standard Model (SM), and a massive invisible particle. It is well known that the mass difference
can be extracted from the endpoint of a transverse kinematic variable like the transverse mass, $M_T$ ,
or the Cambridge $M_{T2}$ variable, but measuring the overall mass scale is a very difficult problem.
We show that the MEM can be used to obtain not only the absolute mass scale, but also the width
of the resonance and the tensor structure of its couplings. Apart from new physics searches, our
results can be readily applied to the case of SM W-boson production at the CERN Large Hadron
Collider (LHC), where one can repeat the measurements of the W properties in a more general and
model-independent setup.
We study the LHC sensitivity to a minimal, $W'$-based resolution to the $R(D^{(\ast)})$ anomalies using $b$-tags, hadronic $\tau$s, and missing energy. We show that the $b$-tag requirement can improve the reach over the inclusive analysis for $W'$ masses of 750 GeV and below.
Many extensions of the standard model (including SUSY) predict new particles with long lifetimes, such that the position of their decay is measurably displaced from their production vertex, and particles that give rise to other non-conventional signatures. We present recent results of searches for long-lived particles and other non-conventional signatures obtained using data recorded by the CMS experiment in Run II of the LHC.
Future electron-proton (ep) collider proposals like the LHeC or the FCC-eh can supply 1/ab of collisions with a center-of-mass energy in the TeV range, while maintaining a clean experimental environment more commonly associated with lepton colliders. This makes them ideally suited to probe BSM signatures with final states that look like "hadronic noise" in the high-energy, pile-up-rich environment of hadron colliders. Focusing on the generic vector boson fusion production mechanism, which is available for all BSM particles with electroweak charges, ep colliders can probe mass scales far above the reach of most lepton colliders. This unique experimental environment can be exploited in the search for long-lived particles (LLPs), which are theoretically very highly motivated and can feature in a broad class of BSM theories. In this talk, signals arising from long-lived Higgsinos and exotic Higgs decays will be presented as case studies. At ep colliders, LLPs with soft decay products and very short lifetimes can be probed, thus exploring significant regions of BSM parameter space inaccessible to other collider searches. This also provides important implications for the design of such machines.
This is based on the work presented in arXiv:1712.07135.
Many forms of experimental evidence point to the existence of Dark Matter within the universe. As of yet, however, it's particle nature has not been discovered. Presented will be an overview of run-2 searches for Dark Matter at the ATLAS detector. The focus of the these studies are based on simplified signal models, moving away from the EFT based approach during run-1. An overview of such searches will be given, along with recent results and discussion as to the future of Dark Matter searches at ATLAS.
Searches in CMS for dark matter in final states with invisible particles recoiling against visible states are presented. Various topologies and kinematic variables are explored, including jet substructure as a means of tagging heavy bosons. The focus of the talk is the recent results obtained using data collected at Run-II of the LHC.
Assume that dark matter couples mostly to the top-quark. This hypothesis is well motivated in models with scalar mediators, where flavor-hierarchical couplings to quarks prevent large flavor-changing neutral currents. In this talk, we discuss searches for dark matter produced in association with top-quarks at the LHC. We propose single-top-associated production as a new search channel for dark matter. Being complementary to exisiting searches with top pairs, the new single-top channel enhances the discovery potential for dark matter in future LHC analyses.
Dark matter (DM) particles that belong to a multiplet of the standard model (SM) weak interactions are challenging to probe in direct detection experiments due to loop-suppressed cross-sections, while indirect detection is a promising avenue if a single particle species saturates the DM relic density. There is, however, a large range of the DM particle mass where it constitutes only a fraction of the total DM relic density (if produced entirely through thermal freeze-out), rendering indirect detection less promising. Direct production at colliders is thus crucial to probe this mass range. Due to the small electroweak production cross-section, and absence of clean experimental handles, searches at hadron colliders remain challenging as well. The current expectations for future runs of the 14 TeV LHC are projected to probe DM masses of around $250$ GeV for an ${\rm SU}(2)$ doublet (Higgsino-like), and $800$ GeV for an $\rm{SU} (2)$ triplet (wino-like). In this paper, we estimate how far this mass reach can be extended at the proposed 27 TeV high-energy upgrade of the LHC (HE-LHC), and compare the results to the case for a 100 TeV hadron collider. With the new B-layer inserted in the ATLAS tracking system for the Run-2 LHC upgrade, a disappearing charged track analysis at the HE-LHC can probe Higgsino-like (wino-like) DM mass of up to $600$ GeV ($2.1$ TeV) at the $95\%$ C.L., making it complementary to the indirect probes using gamma rays from dwarf-spheroidal galaxies. The monojet and missing transverse momentum search, on the otherhand, has a weaker reach of $490$ GeV ($700$ GeV) at $95\%$ C.L. for the Higgsino-like (wino-like) states.
I will discuss LHC phenomenology of dark matter "candidates" which decay invisibly inside the detectors, proposing to test for this possibility by studying the effect of particle widths on the observable invariant mass distributions of the visible particles seen in the detector. I consider the simplest non-trivial case of a two-step two-body cascade decay and derive analytically the shapes of the invariant mass distributions, for generic values of the widths of the new particles. I demonstrate that the resulting distortion in the shape of the invariant mass distribution can be significant enough to measure the width of the dark matter "candidate", excluding it as the source of the cosmological dark matter.
We explore the possibility that bound states involving dark matter particles could be detected by resonance searches at the LHC, and the generic implications of such scenarios for indirect and direct detection. We demonstrate that resonance searches are complementary to mono-jet searches and can probe dark matter masses above 1 TeV with current LHC data. We argue that this parameter regime, where the bound-state resonance channel is the most sensitive probe of the dark sector, arises most naturally in the context of non-trivial dark sectors with large couplings, nearly-degenerate dark-matter-like states, and multiple force carriers. The presence of bound states detectable by the LHC implies a minimal Sommerfeld enhancement that is appreciable, and potentially also radiative bound state formation in the Galactic halo, leading to large signals in indirect searches. We calculate these complementary constraints, which favor either models where the bound-state-forming dark matter constitutes a small fraction of the total density, or models where the late-time annihilation is suppressed at low velocities or late times. We present concrete examples of models that satisfy all these constraints and where the LHC resonance search is the most sensitive probe of the dark sector.
In this talk, I will discuss the phenomenology of dark matter bound states at the LHC. Dark matter particles could form bound states due to the self-interaction mediated by dark force carriers. For example, we find bound state formation in large parameter space of the self-interacting dark matter (SIDM) model that explains the small scale structure problems in astrophysical observations. The bound states produced at the LHC annihilate into light mediators, which could decay inside the detector if they're long-lived. We use LHC result to put constraints on bound state production rate and mediator lifetime in dark photon model.
Supernova 1987A provides strong constraints on dark-sector particles with masses below ~100 MeV. If such particles are produced in sufficient quantity, they reduce the cooling time of the supernova, in conflict with observations. We consider the resulting constraints on dark photons, sub-GeV dark matters coupled to dark photons, milli-charged particles and axions. For the first time, we include the effects of finite temperature and density in this environment, and we estimate the systematic uncertainties on the cooling bounds by varying temperature and density profiles of the proto-neutron star. Furthermore, our new treatment on particle trapping increases the upper bounds by an order of magnitude. In conclusion, our constraints exclude novel parameter spaces for sub-GeV dark matter, and for dark photons and axions differs significantly from previous work in the literature.
The sensitivity of direct-detection experiments looking for sub-GeV dark matter is bounded below as sufficiently weakly interacting dark matter does not produce enough events to be detected. However, the sensitivity is also bounded above as sufficiently strongly interacting dark matter is slowed down below the threshold by its interactions with the medium above the experiment. The upper sensitivity limits of surface experiments are determined by the interactions of dark matter with the atmosphere and those for the deep underground experiments are determined by the interactions of dark matter with the crust of the earth. In this talk, I will present the upper bounds on the sensitivities of the experiments like SENSEI and XENON10/100 for both ultralight and heavy mediator. I will also briefly discuss the prospects of changing the height of the experiment above the ground or changing the depth of the experiment below the ground.
Many dark matter studies have considered indirect detection~($\chi\chi\rightarrow f f$), direct detection~($\chi f\rightarrow \chi f$), and collider searches~($f f\rightarrow \chi \chi$). We propose a new strategy in searching for dark matter elastic cross section by considering cosmic-ray propagation in the galactic dark matter halo. We find that cosmic rays can lose significant fraction of their energy through scattering with dark matter~($f \chi \rightarrow f \chi$). Using existing cosmic-ray data and a simple cosmic-ray propagation model, we study the qualitative effects of dark matter scattering on cosmic-ray propagation and obtain new constraints of dark matter elastic cross sections on light dark matter~(keV--GeV), a regime that is difficult for traditional direct detection experiments to probe.
ABRACADABRA10cm is a new experiment which seeks to detect
axion dark matter through its interactions with the electromagnetic field. The experiment, which is planned to start collecting data this year, will probe unstudied regions of axion parameter space and lay the groundwork for future, larger-scale efforts. I will discuss the results of numerical and analytical work towards understanding the signatures of axion dark matter substructure in the experiment. In particular, I will focus on the effects of dark matter streams, especially as informed by cosmological N-body simulation data.
We propose a "Light Shining Through Walls"-type experiment to search for axions using high-Q superconducting RF cavities. Our setup uses a gapped toroid to confine a static magnetic field, with production and detection cavities positioned in regions of vanishing external field. We argue that the confining toroid does not significantly screen the axion-induced signal for frequencies of order the inverse toroid size. This setup allows both cavities to be superconducting with quality factors Q ~ 10^10, thus significantly improving the sensitivity of the experiment. Such a search has the potential to probe axion-photon coupling down to g ~ 2 x 10^-11 GeV^-1, comparable to the future ALPS II.
Dark matter could be a thermal relic of strongly-interacting massive particles (SIMPs), where 3→2 self interactions set the relic density. This number-changing process has been shown to be generic in theories of chiral symmetry breaking, where the number-changing processes are sourced by the Wess-Zumino-Witten term. Due to conservation of comoving entropy, the 3→2 process heats the remaining dark matter. In order for dark matter to form cosmological structure consistent with observation, a cooling mechanism must be present during the time of dark matter freezeout. I will explore models in which an axion-like particle mediates kinetic equilibrium between the dark and visible sectors. I will demonstrate the viability of such models when the pseudoscalars couple to the visible sector via photons or electrons. Interestingly, the visible-sector couplings necessary to produce the observed dark matter relic abundance will soon be probed by experiments.
A nonrelativistic effective field theory for a real Lorentz-scalar axion field $\phi$ is most conveniently formulated in terms of a complex scalar axion field $\psi$. There have been several recent derivations of classical effective Lagrangians for the complex field $\psi$ in which the effective potential was determined to order $(\psi^* \psi)^3$ for specific interaction potentials $V(\phi)$. In this talk, I will show that the different effective Lagrangians agree with the first derivation of the effective Lagrangian in axion EFT where the effective potential was determined to order $(\psi^* \psi)^5$ for the most general interaction potential $V(\phi)$ with $Z_2$ symmetry.
At the LHC, searches for the pair production of strongly-interacting supersymmetric particles profit from high cross sections, and mass limits set in the context of simplified models reach up to about 2 TeV for gluinos, and 1-1.5 TeV for squarks. The talk will cover searches based on pp collisions recorded at sqrt(s) = 13 TeV with the CMS experiment in final states with 0, 1, 2, or more leptons, and significant missing transverse energy.
Despite the absence of experimental evidence, weak-scale supersymmetry remains one of the best-motivated and studied Standard Model extensions. This talk summarises recent ATLAS results on inclusive searches for supersymmetric squarks and gluinos, including third-generation squarks produced in the decay of gluinos. The searches involve final states containing jets, missing transverse momentum with and without light leptons, taus or photons, and were performed with pp collisions at a centre-of-mass energy of 13 TeV.
Without clear evidence of new physics in LHC data thus far, it has become increasingly important to critically analyze the data in a model-independent fashion. We present such a technique, which we call "Rectangular Aggregations", and apply it to a CMS jet+MET SUSY search. We identify a previously overlooked excess with low jet multiplicity and low MET and HT, which we refer to as a "monojet excess". In the combined ATLAS and CMS data, we find a local (global) preference of 3.3 (2.5)σ, when interpreted as the resonant production of a heavy colored state decaying to a quark and a massive invisible particle. Some suggestions for improved sensitivity to this model as an explanation for this excess are also discussed.
Searches for supersymmetry are a key focus of the LHC experimental program. In particular, natural SUSY models motivate third generation squarks with masses light enough to be produced at the LHC. As a result, the ATLAS experiment has a variety of analyses devoted to stop/sbottom direct production. In this talk, recent results from these searches for are discussed, and the current stop/sbottom mass exclusion limits are presented.
Supersymmetric partners of third-generation quarks play a crucial role in models of natural supersymmetry. The talk reports on results of searches for top and bottom squarks, based on pp collisions recorded during LHC Run 2 by the CMS experiment. The searches cover final states with 0, 1, or 2 leptons and are interpreted in simplified models that cover different kinematic domains defined by the mass difference between the squark and the lightest supersymmetric particle
This paper is based on arXiv:1802.00448 where we construct the complete set of minimal 3-point vertices for the massive Standard Model (SM) based purely on symmetry principles, mass dimension and high-energy behavior and without any recourse to field theory, gauge symmetries or Feynman rules. Because the gravitational vertices are no more challenging than any other vertices in this constructive method, we include them as well. We also calculate the high-energy behavior of these vertices and compare with the well-known massless vertices, both as a check and as a way to pin down the normalization constants. We include all these vertices in tables as a reference for future investigations.
A gauge theory with the gauge group $SU(2)_L$ is the simplest non-abelian spontaneous symmetry breaking theory. Its’ simplest bosonic representation is a complex scalar doublet in the linear representation with a scalar $h$, pseudoscalars $\vec{\pi}$ and vector gauge bosons $\vec{W}_{\mu}$. We observe that the on-shell T matrix elements of physical states are independent of global $SU(2)_L$ global transformations and the current corresponding to these global transformations is conserved exactly on the amplitudes of physical states. We identify two towers of 1-soft-pion Ward-Takahashi Identities which govern the scalar sector, and represent a symmetry which we call $SU(2)_L \otimes$BRST, a symmetry not of the Lagrangian but the physical states. The first tower gives relations among 1-$\phi$-I off-shell Green’s functions and the second tower governs on-shell T-matrix elements and replaces Adler self-consistency conditions with those for gauge theories. The T-matrix identities ensure IR finiteness of the theory despite zero Goldstone boson mass and include the LSS theorem which enforces the condition of masslessness on the pseudoscalars, a far stronger statement than the usual masslessness of the Goldstone bosons. The global $SU(2)_L$ and BRST transformations commute in $R_{\xi}$ gauges. With the on-shell constraints, the physics therefore has more symmetry than does its BRST invariant Lagrangian. In a previous work, some of us have shown that the above results hold for the Abelian Higgs Model.
References: arXiv: 1711.07349 (submitted to Phys. Rev. D)
Phys. Rev. D 96, 065006 (2017)
A lattice version of the widely used Functional Renormalization Group (FRG) for the Legendre effective action is solved (exactly) in terms of a linked cluster expansion. The graph rules invoke only one-line irreducible graphs and a new type of labeled tree graphs. Conversely the FRG induces nonlinear flow equations governing suitable resummations of the graph expansion. The correspondence is tested on the critical line of the Luscher-Weisz solution of phi^4 theory. An extension to quantum field theories on curved spacetimes with flat spatial sections is feasible.
Recent lattice calculations have shown that confining gauge theories with a number of light fermion flavors just below the critical value for transition to infrared conformal behavior possess a light scalar composite state. Such nearly conformal gauge theories could be responsible for the breaking of electroweak symmetry with the light scalar interpreted as a Composite Higgs. Finding a reliable EFT description of the lowest mass states in these gauge theories would aid the understanding of their phenomenology. I will talk about recent work in which lattice data from two different nearly conformal gauge theories were fitted to dilaton EFTs and similarities between the fit results were identified. An EFT based on the linear sigma model could also be a good low energy description. Different power counting schemes for this EFT and their physical consequences will be outlined.
We construct asymptotically safe extensions of the Standard Model by adding gauged vector-like fermions. Using large number-of-flavour techniques we argue that all gauge couplings, including the hypercharge and, under certain conditions, the Higgs coupling can achieve an interacting ultraviolet fixed point.
Soft Collinear Effective Theory (SCET) has originally been developed in the framework of QCD. SCET for QCD facilitates calculation of scattering amplitudes for jets of highly collimated and energetic particles with soft radiations in a systematic and efficient way. A small parameter, $\lambda$, is used to describe the soft and collinear regions of the phase space. As a consequence the Lagrangian of SCET is an expansion in powers of $\lambda$. We have developed Soft Collinear Effective Theory for gravity at leading and next-to-leading powers in $\lambda$. Being an effective theory, SCET for gravity is halfway between full theory of gravity (below Planck scale) and gravity amplitudes. This reveals many interesting properties of gravity amplitudes which are obscure in full theory and usually need lengthy calculations or ingenious tricks to realize. For example, soft graviton theorem and absence of collinear IR divergences at the leading power are manifest in the Lagrangian of our effective theory.
A SCET for gravity that describes N different collinear directions, effectively has N copies of the diffeomorphism (diff) invariance of the full theory. This suggests that the original S-matrix, which contains all gravity SCETs with all values of N, should have an infinite number of effective diff invariances. It would be interesting to explore the connection between this and the infinite-dimensional symmetries of gravitational scattering amplitudes, known as BMS invariance in the literature. In the literature nonlocal “dressings” have been found by speculating what might be the fundamental observables in the ultimate theory of gravity, while in our gravity SCET we are led to specific forms of these dressings as a consequence of invariance under the N copies of diff. We call these dressings in analogy with QCD SCET, diff Wilson lines. As a future direction it is interesting to find relations between leading and next-to-leading power terms by using Reparametrization Transformation Invariance (RPI), that essentially restores Lorentz invariance “broken” by choosing a preferred direction for collinear particles. It is also possible that RPI should be changed when considering gravity.
We propose the Domain-Wall(DW) Standard model(SM), where all the SM fields are localized in a non-compact 5D space-time. The DWSM has several interesting implications. Particularly, the interplay between DW fermions and DW gauge bosons is dependent on their mutual configuration in the 5D bulk. By localizing left and right-handed fermions in different places throughout the bulk, this introduces differences in coupling strength to the Kaluza-Klien(KK) gauge fields. These differences can be explored through future experiments at the Large Hadron Collider once a KK-mode of the SM gauge boson is discovered. Additionally, constraints on the sequential SM W' and Z' boson masses enable us to interpret a lower bound on the lowest KK-mode SM gauge boson masses. Other interesting phenomenology considered include effects of the KK-mode SM fermion on the Higgs boson, and KK-mode fermion decays into SM fermions and a NG boson associated with breaking of translational invariance in the 5th dimension.
A summary of recent ATLAS results on top pair production, both differential and associated production.
Recent advances in machine learning have made it possible for convolutional neural networks to be applied to classifying boosted jets as either signal (be that tops, Ws or Higgses) or QCD background. These techniques have shown comparable and even superior performance to QCD-based taggers, although have typically relied on constructing 2D ‘images’ of the jets. In this talk, I discuss a new, more physics-motivated approach, where the four-momenta of the jet constituents are used directly as inputs for the network, and highlight the advantages of this approach over the usual jet images method.
Many theories beyond the Standard Model predict new phenomena which decay to energetic top quarks. Searches for such new physics models are performed using the ATLAS experiment at the LHC using proton-proton collision data collected in 2015 and 2016 with a center-of-mass energy of 13 TeV. Selected recent results will be discussed.
Measurements of single top-quark production in proton-proton collisions are presented based on the 13 TeV and 8 TeV ATLAS datasets. In the leading order process, a $W$-boson is exchanged in the t-channel. The cross-section for the production of single top-quarks and single antitop-quarks, their ratio, as well as differential cross-section measurements are also reported. Measurements of the inclusive and differential cross-sections for the production of a single top quark in association with a $W$-boson, the second largest single top production mode are also presented. Evidence for the s-channel single top-quark production in the 8 TeV dataset is presented. Finally, the first measurement of the $tZq$ electroweak production is presented. All measurements are compared to state-of-the art theoretical calculations. (On behalf of the ATLAS collaboration)
We present progress on our calculation of next-to-leading order QCD effects in single top production for a precision determination of the Wtb coupling. The calculation is performed analytically including an off-shell top quark and includes relevant operators from the Standard Model Effective Field Theory (SMEFT) that modify the Wtb coupling. We discuss the phenomenological importance and put our calculation into the context of current studies.
We study the effect of multiple soft gluon radiation on the kinematical distributions of the $t$-channel single top quark production at the LHC. By applying the transverse momentum dependent factorization formalism, large logarithms (of the ratio of large invariant mass Q and small total transverse momentum $q_\perp$ of the single-top plus one-jet final state system) are resummed to all orders in the expansion of the strong interaction coupling at the accuracy of next-to-leading logarithm, including the complete next-to-leading order corrections. We show that the main difference from PYTHIA prediction lies on the inclusion of the exact color coherence effect between the initial and final states in our resummation calculation, which becomes more important when the final state jet is required to be in the forward region. We further propose a new experimental observable $\phi^*$ to test the effect of multiple gluon radiation in the single-top events. The effect of bottom quark mass is also discussed.
We consider a TeV vector like Top Partner that is a color triplet and electroweak singlet. We study the pair production of the Top Partner at the LHC and its radiative decay modes into SM top and gloun or SM top and photon. The interaction Lagrangian of the Top Partner with SM top is introduce as an effective dimension 5 operator. We focus on the semileptonic final states and use Boosted Tagging Technique to identify heavy objects and reduce the background. We then study the signal sensitivity of the LHC by presenting luminosity curves and branching ratio as a function of the top partner mass.
Classification Without Labels (CWoLa) is a Machine Learning strategy which can be used to classify event categories (e.g. quark jet vs gluon jet, or BSM signal vs SM background) starting from mixed event samples, which are inevitable at the LHC. I will illustrate how this strategy can be used to uncover BSM resonance signals which would otherwise be completely buried under large SM backgrounds by talking advantage of as much information as possible about the events, focusing on a toy example where a di-fat jet resonance with unusual jet substructure is hidden amongst standard model dijets. This strategy can be applied directly to data without a need for any specific signal model, simulated signal or background Monte Carlo events, or carefully chosen cuts.
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, such as T', are also considered. We explore the use of jet substructure techniques to reconstruct highly boosted objects in events, enhancing the sensitivity of these searches.
We present results of searches for massive vector-like top and bottom quark partners 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. We search using several categories of reconstructed objects, from multi-leptonic to fully hadronic final states. We set exclusion limits on both the vector-like quark mass and cross sections, for combinations of the vector-like quark branching ratios.
Numerous new physics models, e.g., theories with extra dimensions and various gauge-group extensions of the standard model, predict the existence of new heavy resonances. Results of searches for new particles such as heavy bosons, leptoquarks, heavy neutrinos in final states with leptons, photons and jets are presented. The emphasis is given to the recent results obtained using data collected at Run-II of the LHC.
We investigate an excess observed in hadronic events in the archived LEP2 ALEPH data. The events are clustered into four jets and paired such that the mass difference between the two dijet systems is minimized. The excess occurs in the region $M_1+M_2\sim 110\mbox{ GeV}$; about half of the excess is concentrated in the region $M_1\sim 80\mbox{ GeV}$, $M_2\sim 25\mbox{ GeV}$, with a local significance between $4.7\sigma$ and $5.5\sigma$, depending on assumptions about hadronization uncertainties. The other half of the events are in a broad excess near $M_1\sim M_2\sim 55\mbox{ GeV}$; these display a local significance of $4.1-4.5\sigma$. We investigate the effects of changing the SM QCD Monte Carlo sample, the jet-clustering algorithm, and the jet rescaling method, finding that the excess is remarkably robust under these changes, and we find no source of systematic uncertainty that can explain the excess. No analogue of the excess is seen at LEP1. We conclude that this excess should be investigated by the other LEP experiments and QCD experts.
Many new physics models, such as compositeness, see-saw, or extra dimension models, are expected to manifest themselves in final states with leptons, photons or jets. This talk presents searches for new non-resonant phenomena in various final states, focusing on recent results obtained using data collected at Run-II of the LHC.
The LEP experiment at CERN provided accurate measurements of the Z neutral gauge boson properties. Although all measurements agree well with the SM predictions, the forward backward asymmetry of the bottom-quark remains almost 3σ away from the SM value. We proposed that this anomaly may be explained by the existence of a new U(1)D gauge boson, which couples with opposite charges to the right-handed components of the bottom and charm quarks. Cancellation of gauge anomalies demands the presence of a vector-like singlet charged lepton as well as a neutral Dirac (or Majorana) particle that provides a Dark Matter candidate. Constraints from precision measurements imply that the mass of the new gauge boson should be around 115 GeV. We discuss the experimental constraints on this scenario, including the existence of a di-jet resonance excess at an invariant mass similar to the mass of this new gauge boson, observed in boosted topologies at the CMS experiment.
Hints for new physics beyond the standard model at the LHC are scarce. An exception are B-anomalies reported by LHCb in R_K and R_K* measurements, the latter two combining to a 4 sigma deviation from the SM.
A possible explanation of this excess might be a new heavy neutral gauge boson Z' with flavour-conserving couplings to second and third generation leptons, as well as third generation quarks, in addition to a flavour-violating b-s coupling. This talk presents search strategies and prospects for such a hypothetical particle in the dimuon channel within a Delphes study.
We propose a grand unified SU(5)$\times$U(1)$_X$ model, where the standard SU(5) grand unified theory is supplemented by minimal seesaw and a right-handed neutrino dark matter with an introduction of a global $Z_2$-symmetry. In the presence of three right-handed neutrinos (RHNs), the model is free from all gauge and mixed-gravitational anomalies. The SU(5) symmetry is broken into the Standard Model (SM) gauge group at $M_{\rm GUT} \simeq 4 \times 10^{16}$ GeV in the standard manner, while the $U(1)_X$ symmetry breaking occurs at the TeV scale, which generates the TeV-scale mass of the $U(1)_X$ gauge boson (Z′ boson) and the three Majorana RHNs. A unique $Z_2$-odd RHN is stable and serves as the dark matter (DM) in the present Universe, while the remaining two RHNs work to generate the SM neutrino masses through the minimal seesaw. We investigate the Z′-portal RHN DM scenario in this model context, and find that the constraints from the DM relic abundance and the search results for a Z′ boson resonance at the Large Hadron Collider (LHC) are complementary to narrow down the allowed parameter region, which will be fully covered by the future LHC experiments (for the Z′ boson mass < 5 TeV). We also briefly discuss the successful implementation of Baryogenesis and cosmological inflation scenarios in the present model.
If dark matter annihilation is velocity dependent, then the J-factors associated with any astrophysical target depend on the full dark matter phase space distribution. We calculate these velocity-dependent J-factors for a variety of targets and a variety of choices for the velocity-dependence of DM annihilation. Significantly, we find that the choice of velocity-dependence affects the relative importance of different dwarf spheroidal galaxies for dark matter searches, relative to each other and to the Galactic Center, and can affect the morphology of any signal from the Galactic Center.
A leading dark matter candidate is a Weakly Interacting Massive Particle (WIMP). The observed dark matter abundance can be naturally obtained through freezeout of the thermal annihilation rate. The defining feature of a thermal WIMP is that its total annihilation cross section is specified through the thermally averaged cross section $\langle\sigma v\rangle$. Searches for dark matter annihilation products have set strong limits in certain cases, requiring that the dark matter mass be greater than about 100 GeV if annihilation proceed solely to $b$ quarks (Fermi), $\tau$ leptons (Fermi), or electrons (AMS). We construct the first limits on the WIMP total annihilation cross section, showing that allowed combinations of the annihilation-channel branching ratios considerably weaken these limits. We show that GeV-mass thermal WIMPs have not yet been adequately tested, and outline ways forward.
We study a simple model of thermal dark matter annihilating to standard model neutrinos via the neutrino portal. A (pseudo-)Dirac sterile neutrino serves as a mediator between the visible and the dark sectors, while an approximate lepton number symmetry allows for a large neutrino Yukawa coupling and, in turn, efficient dark matter annihilation. The dark sector consists of two particles, a Dirac fermion and complex scalar, charged under a symmetry that ensures the stability of the dark matter. A generic prediction of the model is a sterile neutrino with a large active-sterile mixing angle that decays primarily invisibly. We derive existing constraints and future projections from direct detection experiments, colliders, rare meson and tau decays, electroweak precision tests, and small scale structure observations. Along with these phenomenological tests, we investigate the consequences of perturbativity and scalar mass fine tuning on the model parameter space. A simple, conservative scheme to confront the various tests with the thermal relic target is outlined, and we demonstrate that much of the cosmologically-motivated parameter space is already constrained. We also identify new probes of this scenario such as multibody kaon decays and Drell-Yan production of W bosons at the LHC.
We explain the two upgoing ultra-high energy shower events observed by ANITA as arising from the decay in the Earth’s interior of the quasi-stable dark matter candidate in the CPT symmetric universe. The dark matter particle is a 480 PeV right-handed neutrino that decays into a Higgs boson and a light Majorana neutrino. The latter interacts in the Earth’s crust to produce a τ lepton that in turn initiates an atmospheric upgoing shower. The fact that both events emerge at the same angle from the Antarctic ice-cap suggests an atypical dark matter density distribution in the Earth.
Near a critical value of the wino mass where there is a zero-energy S-wave resonance at the neutral-wino-pair threshold, low-energy winos can be described by a zero-range effective field theory (ZREFT) in which the winos interact nonperturbatively through a contact interaction and through Coulomb interactions. The effects of wino-pair annihilation into electroweak gauge bosons are taken into account through the analytic continuation of the real parameters for the contact interaction to complex values. The parameters of ZREFT can be determined by matching wino-wino scattering amplitudes calculated by solving the Schroedinger equation for winos interacting through a real potential due to the exchange of electroweak gauge bosons and an imaginary potential due to wino-pair annihilation into electroweak gauge bosons. ZREFT at leading order gives an accurate analytic description of low-energy wino-wino scattering, inclusive wino-pair annihilation, and a wino-pair bound state. ZREFT can also be applied to partial annihilation rates, such as the Sommerfeld enhancement of the annihilation rate of wino pairs into monochromatic photons.
Observational evidence for dark matter stems from its gravitational interactions, and as of yet there has been no evidence for dark matter interacting via other means. We examine models where dark matter interactions are purely gravitational in a Randall-Sundrum background. In particular, the Kaluza-Klein tower of gravitons which result from the warped fifth dimension can provide viable annihilation channels into Standard Model final states, and we find that we can achieve values of the annihilation cross section, ⟨σv⟩, which are consistent with the observed relic abundance in the case of spin-1 dark matter. We examine constraints on these models employing both the current photon line and continuum indirect dark matter searches, and assess the prospects of hunting for the signals of such models in future direct and indirect detection experiments.
Scalar, fermionic, and vector WIMP-like dark matter may couple to the Standard Model through a massive spin-2 mediator. Mediators of this sort appear in extra-dimensional models, such as Randall-Sundrum models. We apply several parameter space constraints to phenomenological spin-2 mediated scenarios, including those arising from direct detection, indirect detection, relic density, collider experiments, and unitarity.
The CMS experiment has a wide program on heavy flavor physics, covering production and decay properties of B hadrons and quarkonia, as well as searches and study of exotic hadrons and rare decays. In this talk, we present precise measurements of B hadron lifetimes, that are good as or better than previous measurements. Recent measurements of the Lambda_b polarization and angular parameters in Lambda_b -> J/psi Lambda decays are also presented and compared to various theoretical predictions. On the other hand, measurements at 13 TeV of psi(nS) (n=1,2) and Upsilon(nS) (n=1,2,3) production cross sections are shown and compared with theoretical expectations as a function of transverse momentum and rapidity. Finally, we discuss the latests results from CMS on the search for exotic resonances (the controversial X(5568)) in the B_s pi+ mass spectrum.
There has been persistent ($>3\sigma$) disagreement between the Standard Model prediction and experimental measurements of $R_{D^{(*)} }=\mathcal{B}(B \rightarrow D^{(*)} \tau \nu_\tau)/\mathcal{B}(B \rightarrow D^{(*)} l \nu_l)(l=e,\mu)$. This anomaly may be addressed by introducing interactions beyond the Standard Model involving new states, such as leptoquarks. In this talk, I look at the constraints on third generation scalar leptoquarks from electroweak precision measurements at LEP and SLC. Among the electroweak observables, the partial decay width of $Z \rightarrow \tau\bar{\tau}$ places the strongest constraints. If one assumes Minimal Flavor Violation (MFV) in the quark sector, the leptoquarks masses and couplings required to satisfy the $R_{D^{(*)}}$ anomaly are strongly disfavored by electroweak data. Without MFV, one may still avoid electroweak constraints and address the anomaly.
We present the effects of new physics operators with different Lorentz structures on the inclusive $B \to X_c\tau \bar{\nu}$ decay and make predictions for the ratio of total decay rates, $R(X_c)$ and some differential observables including the forward-backward asymmetry. We include $\mathcal{O}(\alpha_s)$ radiative and $1/m_b$ non-perturbative corrections to these observables in the Standard Model (SM). We also present some leptoquark models as explicit examples of new physics effects.
There are presently many different anomalies in $B$-physics. One such anomaly is ${R_{K^{(*)}}}$, the apparent deficit of decays $B \rightarrow K \mu \mu$ compared to $B \rightarrow K e e$. In this talk, I will attempt to explain this apparent violation of lepton flavour universality within a supersymmetric framework. To do so, I will invoke the $R$-partiy violating superpotential term $\lambda' LQD^c$ and then study potential wino contributions. This will lead to a spectrum of sparticles consisting of winos and left-handed up squarks with masses of order $1 \ \text{TeV}$ and right-handed down squarks and sneutrinos with masses of order $10 \ \text{TeV}$. Potential constraints from low energy processes and direct LHC searches are examined and other features of the model such as Landau poles and neutrino masses will be discussed.
We search for the decay $B_s \to \eta^\prime K_s$ using $121.4 {\rm
~fb^{-1}}$ of data collected at the $\Upsilon(5S)$ resonance with the
Belle detector at the KEKB asymmetric-energy electron-positron collider.
This decay is suppressed in the Standard Model of particle physics and
proceeds through $b \to u$ and penguin transitions, which are sensitive
to new physics. The expected branching fraction in the Standard Model is
approximately $2 \times 10^{-6}$. This decay has not been observed yet.
We use Monte Carlo simulation to study Belle sensitivity to these
decays. We report the current status of our investigations to provide
the best sensitivity to discovering this decay in the existing data.
The momentum distributions for the $D^0\bar{D}^0\pi^0$ and $D^0\bar{D}^0\gamma$ decay modes of the X(3872) resonance are calculated with the widths of $D^{*0}$ and X(3872) taken into account. The momentum distributions for the $D^0$ have a double peaked structure, with the first peak below 10 MeV and the second peak near 40 MeV for the $D^0\bar{D}^0\pi^0$ decay mode and near 140 MeV for the $D^0\bar{D}^0\gamma$ decay mode. The widths of the peaks are sensitive to the binding energy and width of the X(3872).
The standard model does not provide an explanation of the observed alignment of quark flavors i.e. why are the up and down quarks approximately aligned in their weak interactions according to their masses? We suggest a resolution of this puzzle using a combination of left-right and Peccei-Quinn (PQ) symmetry. The quark mixings in this model vanish at the tree level and arise out of one loop radiative corrections which explains their smallness. The lepton mixings on the other hand appear at the tree level and are therefore larger. We show that all fermion masses and mixings can be fitted with a reasonable choice of parameters. The neutrino mass fit using seesaw mechanism requires the right handed WR mass bigger than 18 TeV. Due to the presence of PQ symmetry, this model clearly provides a solution to the strong CP problem.
I would briefly describe what Quantum Critical Higgs models are, what some of their five dimensional dual models are, and their signature is in the gg --> ZZ —> 4l Chanel.
The measurement of the Higgs boson's production and decay rates and its couplings to vector bosons and fermions, based on the data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, delivered by the CERN LHC in 2016, corresponding to an integrated luminosity of 35.9 fb $^{-1}$, is presented. Several parametrizations and interpretations of the results are considered. All the measurements are in agreement, within the uncertainties, with the Standard Model predictions, in all the parametrizations considered.
The precise measurement of the properties of the Higgs boson is one of the main goal of the physics research at the LHC. The presentation shows the new results achieved by the ATLAS collaboration in the bosonic Higgs decay channels ($H\rightarrow\gamma\gamma$, $H\rightarrow ZZ^*$, $H\rightarrow WW^*$) using 36 fb$^{−1}$ of proton-proton collision data recorded at $\sqrt{s}= 13$ TeV during the 2015 and 2016. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vector-boson fusion, and in association with a vector boson or a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. Moreover measurements of simplified template cross sections, designed to quantify the different Higgs boson production processes in specific regions of phase space, are reported. Finally the presentation shows the measurement of the fiducial cross-section of the production of the Higgs boson and the differential and double-differential cross-section measurements related to the Higgs boson kinematics as well as the kinematics and multiplicity of the jets produced in association with a Higgs boson.
The 125 GeV Higgs completes the Standard model particle roster, while offering new opportunities for looking for physics beyond. We focus on certain kinematics at off-shell Higgs signal region that probe the Higgs sector, especially the ability to distinguish among Standard model and generic new physics scenarios.
No matter what the scale of new physics is, deviations from the Standard Model for the Higgs observables will indicate the existence of such a scale. We consider effective six dimensional operators, and their effects on the Higgs productions and decays to estimate this new scale. We analyze and identify the parameter space consistent with known properties of the Higgs boson using recent Run II results from ATLAS and CMS experiments corresponding to ∼ 37 inverse femtobarn of data. We then calculate the t¯th productions, as well as double Higgs production at the LHC using the effective couplings and show that these can be much different than those predicted by the Standard Model, for a wide region of allowed parameters space. These predictions can be tested in the current or the future runs of the LHC. We find that the data are consistent with the existence of a new physics scale as low as 500 GeV for a significant region of parameter space of this six-dimensional couplings with these new physics effects at the LHC. We also find that for some region of the parameter space, di-Higgs production can be much larger than that predicted by the Standard Model giving rise to the prospect of its observation even in the current run II of the LHC.
The LHC experimental discovery of the Higgs boson, along with the measurement of Higgs properties suggests that the SM is a valid effective theory at the weak scale. The lack of new particles up to the TeV scale makes possible the parameterization of possible high scale physics effects in terms of higher dimension operators containing only SM fields (SMEFT). In this talk I will present the computation of the NLO corrections to the Higgs decays to Z boson pairs and Z$\gamma$ in the context of the SMEFT. This is a precursor of the eventual one-loop $H\to Z \bar{f} f$ SMEFT calculation.
In this talk, I will discuss the present status of the Higgs boson's properties since its discovery in 2012. I will focus on the measurements of the various Higgs couplings in several standard decay modes in the context of an effective field theory by introducing dimension-6 (D6) operators. I shall show that considering the effects of the D6 operators on the experimental cut-efficiencies might become important in exploring such couplings. I will also discuss the possibility of strongly constraining the couplings affecting the triple gauge boson vertices by studying the ZH channel in the boosted Higgs regime. I will show the potential of the High luminosity run of the LHC to constrain such couplings to stronger degrees than LEP had constrained earlier.
Standard model is successful in explaining Higgs physics, however new physics beyond the standard model may yet be expected. We study how the inclusion of real singlet scalar and dimension 5 operators effect SM Higgs physics. We do this by studying the deviations of the total width and branching ratios of the Higgs from the SM predictions. We also study the limit on scalar mixing angle and Wilson coefficients by a fit to the combined ATLAS/CMS gluon fusion signal strength for the Higgs production as well as by a fit to the combined ATLAS/CMS signal strengths for the different Higgs decay channels.
Studying the properties of Standard Model (SM) – like Higgs boson becomes one important window to explore the physics beyond the SM. In this work, we present studies about the implications of the Higgs and Z-pole precision measurements at future Higgs Factories. We perform a global fit to various Higgs search channels to obtain the 95% C.L. constraints on the model parameter spaces of Two Higgs Double Model (2HDM) and Minimal Supersymmetric Standard Model (MSSM). In the 2HDM, we analyze tree level effects as well as one-loop contributions from the heavy Higgs bosons. The strong constraints on cos(β − α), mΦ and heavy Higgs mass splitting can be complementary to direct search of the LHC and Z pole precision measurements. For the MSSM, we study both the Higgs couplings and mass precision. The constraints on the CP-odd Higgs mass MA and stop mass scale MSUSY can be complementary to the direct search of HL-LHC. We also compare the sensitivity of various future Higgs factories, namely Circular Electron Positron Collider (CEPC), Future Circular Collider (FCC)-ee and International Linear Collider (ILC).
We generalize the type II seesaw framework. Requiring absence of fine-tuning and arbitrarily small parameters leads to dynamical lepton number breaking at the electroweak scale and a rich LHC phenomenology, including a smoking gun signature that allows to distinguish our model from the usual type II seesaw scenario.
A certain class of new physics models includes long-lived, electrically charge-neutral particles. A displaced vertex is a spectacular signature to probe such particles productions at the high energy colliders, with almost zero background. In the context the minimal gauged $B-L$ extended Standard Model (SM), we consider a pair creation of Majorana right-handed neutrinos (RHNs) at the high energy colliders through the production of the SM and the $B-L$ Higgs bosons and their subsequent decays into RHNs. With parameters reproducing the neutrino oscillation data, we show that the RHNs are long-lived and their displaced vertex signature can be observed at the next generation displaced vertex search experiments, such as HL-LHC, MATHUSLA, LHeC, and FCC-eh. We find that the lifetime of the RHNs is controlled by the lightest light neutrino mass, which leads to a correlation between the displaced vertex search and the search limit of the future neutrinoless double beta-decay experiments.
The recent detection of coherent elastic neutrino-nucleus elastic scattering (CE$\nu$NS) by the COHERENT experiment has enabled new area of neutrino physics. Apart from neutrino experiments using the stop pion source, the CE$\nu$NS measurement may be complemented by reactor experiments. We studied this complementarity between the accelerator and reactor CE$\nu$NS experiments for constraining new physics in the form of non-standard neutrino interactions (NSI). Previous studies that have constrained NSI with both oscillation and scattering experiments typically vary one or two NSI parameters when fitting to a given data set. In this talk, however, we consider four flavor-diagonal up and down-type NSI parameters. We demonstrated that a simultaneous analysis with reactor and accelerator experiments, for several different target materials, breaks a degeneracy between up and down flavor diagonal NSI terms that has persisted with neutrino experiments.
This talk will comment on the underlying statistics, model evaluation, application and usage of MultiNest for the optimization of coherent scattering neutrino detection experiments. We will discuss an approach which incorporates signal and background uncertainties leading to parameter estimations and distributions for a given likelihood.
We discuss the future possible uses of this approach within the realm of short baseline coherent neutrino-nucleus scattering searches for sterile neutrinos. It is of interest to optimize a variety of experimental factors such as exposure, and detector distance from the source, with respect to projected sensitivity and resolution.
We
present an effective theory for neutrino interactions with quarks, gluons and photons
that includes operators up to dimension 7. We perform a matching of these opera-
tors into nucleon operators in order to describe low energy processes as the recently
observed coherent scattering on nuclei. We compare the contribution of these new
interactions with the results from COHERENT and CHARM experiments to obtain
bounds on the new couplings both in the low and high energy regime. We finally
review different models that can give rise to such NonStandard Interactions.
We discuss novel ways in which neutrino oscillation experiments can probe dark matter. In particular, we focus on interactions between neutrinos and ultralight (“fuzzy”) dark matter particles with masses of order 10^-22 eV. It has been shown previously that such dark matter candidates are phenomenologically successful and might help ameliorate the tension between predicted and observed small scale structures in the Universe. We argue that coherent forward scattering of neutrinos on fuzzy dark matter particles can significantly alter neutrino oscillation probabilities. These effects could be observable in current and future experiments. We set new limits on fuzzy dark matter interacting with neutrinos using T2K and solar neutrino data, and we estimate the sensitivity of reactor neutrino experiments and of future long-baseline accelerator experiments. These results are based on detailed simulations in GLoBES. We allow the dark matter particle to be either a scalar or a vector boson. In the latter case, we find potentially interesting connections to models addressing various B physics anomalies.
The standard story is that neutrino mass eigenstates are produced as wavepackets at the same point in spacetime and separate along their journey to the detector, which can cause neutrino oscillations to dampen over long baselines. However, we find that when a calculation is done in quantum field theory, making reference to only measured quantities, that a different picture emerges for how neutrinos propagate through spacetime. This could lead to a better understanding of the mechanisms that control the damping of neutrino oscillations.
Near detectors (ND) at neutrino oscillation experiments will be subjected to unprecedented neutrino fluxes. We explore this to encourage the search for leptophilic new physics in rare neutrino scattering processes like neutrino-electron scattering and neutrino trident production. After addressing some inconsistencies with previous rates for neutrino trident production in the SM, we present revised rates and show that backgrounds can be kept under control. We then discuss the impact of leptophilic $Z^\prime$ models on trident-like processes and show the sensitivities of future near detectors to these enhanced processes.
Supersymmetry is one of the most motivated Standard Model extensions. Despite the meticulous search during the LHC Run I, there is no evidence supporting this theory. Starting from 2015, LHC is performing a second data taking run with a higher center of mass energy (13 TeV), providing a great occasion for the search of beyond the Standard Model physics.
An important sector is the direct production of supersymmetric electroweak particles, such as sleptons and charginos. Electroweak production cross section is lower compared to strong production, but searches performed by the ATLAS and CMS experiments during LHC Run 2 excluded squark and gluinos with masses up to 2 TeV, making electroweak production an increasingly promising probe for SUSY signals at the LHC.
Results obtained with the 2015-2016 ATLAS detector data will be presented. Direct production of electroweak particles like sleptons, charginos and neutralinos, with different signatures, will be considered. A good sensitivity is obtained in the signal regions and Run 1 results are largely improved.
We focus on the triplet and singlet extensions of minimal supersymmetric scenario, where we can see that the electro-weak contributions coming from the additional triplet and singlet are also important and comparable to the strong contributions. In the context of the observed Higgs like particle around 125 GeV, we look into the status of other Higgs bosons in the model. The possibility of light pseudo-scalar gives rise to interesting phenomenology. Doublet-triplet and doublet-singlet mixings in the Higgs sector have implications in the flavour sector as well as give interesting charged Higgs phenomenology. A triplet type charged Higgs boson can be missed in standard searches at collider and we propose some promising channels to distinguish different types of charged Higgs bosons.
R-parity violation introduces many viable signatures to the search for supersymmetry at the LHC. The decay of supersymmetric particles can produce leptons or jets, while removing the missing transverse momentum signal common to traditional supersymmetry searches. Several supersymmetric models also predict massive long-lived supersymmetric particles. Such particles may be detected through abnormal specific energy loss, appearing or disappearing tracks, displaced vertices, long time-of-flight or late calorimetric energy deposits. The talk presents recent results from searches of supersymmetry in these unusual signatures of R-parity violation and long-lived particles with the ATLAS detector.
In this work, we propose to use the timing information (new pico-second timing resolution with detector upgrades) to search for a broad class of BSM signals, such as Higgs decays to glueballs or SUSY long-lived particles.
In a large class of baryogenesis models, where the baryon asymmetry results from the out of equilibrium decay of new weak scale massive meta-stable particle. This is correlated to the proper decay length of the meta-stable particle being larger than 1 mm. We discuss the new search strategies for probing these long lived particles at the LHC with displaced vertices and MET mainly focusing on simplified models with weak scale singlets coupled via Higgs portal.
Results of searches for supersymmetry in events with one or more isolated photons are reported, based on a data set of pp collisions at sqrt(s)=13TeV, recorded by the CMS experiment. Specific searches target events that also feature large missing transverse energy, large hadronic activity and/or isolated leptons. These searches are particularly relevant in the context of gauge-mediated SUSY breaking, where decays of wino- or bino-like neutralinos could produce photons and almost massless gravitinos.
We investigate the possibility of testing supergravity unified models with heavy scalar masses at the Large Hadron Collider. The analysis is carried out under the constraints that models produce the Higgs boson mass consistent with experiment and also produce dark matter consistent with WMAP and PLANCK experiments. A set of benchmarks in the supergravity parameter space are investigated using a combination of signal regions which are optimized for the model set. In the first part of the talk, we examine models with scalar masses in the 50-100 TeV mass range and light gaugino masses that are discoverable at LHC RUN II. Some benchmark models are found to be discoverable with an integrated luminosity as low as 100 fb$^{-1}$ to around 1000 fb$^{-1}$ and thus testable in the high luminosity era of the LHC, i.e., at HL-LHC. It is shown that scalar masses in the 50-100 TeV range but gaugino masses much lower in mass produce unification of gauge coupling constants, consistent with experimental data at low scale, with as good an accuracy (and sometimes even better) as models with low ($\mathcal{O}$(1) TeV) weak scale supersymmetry. Decay of the gravitinos for the supergravity model benchmarks are investigated and it is shown that they decay before the Big Bang Nucleosynthesis (BBN). Further, we investigate the non-thermal production of neutralinos from gravitino decay and it is found that the non-thermal contribution to the dark matter relic density is negligible relative to that from the thermal production of neutralinos for reheat temperature after inflation up to 10$^9$ GeV. In the second part of the talk, we investigate SUSY discovery potential at the HE-LHC, which is the proposed 28 TeV collider at CERN. A set of benchmarks are presented which are beyond the discovery potential of HL-LHC but are discoverable at HE-LHC. For comparison, we study model points at HE-LHC which are also discoverable at HL-LHC. The signatures pertaining to those benchmarks probe the production of electroweakinos and gluinos. For these model points, it is found that their discovery would require a HL-LHC run between 5-8 years while the same parameter points can be discovered in a period of few weeks to $\sim 1.5$ yr at HE-LHC running at its optimal luminosity of $2.5\times 10^{35}$ cm$^{−2}$ s$^{−1}$. The analysis indicates that the HE-LHC possibility should be seriously pursued as it would significantly increase the discovery reach for supersymmetry beyond that of HL-LHC and decrease the run period for discovery.
In non-minimal supersymmetric (SUSY) models, additional tree-level
contributions to the Higgs mass provide a possible solution to the little
hierarchy problem of the minimal supersymmetric standard model (MSSM). This
has generated increased interest in models such as the next-to-MSSM (NMSSM),
on the grounds that they may be more natural than the MSSM. However,
traditional measures of fine-tuning do not provide a well-defined method for
making such comparisons, since the outcome depends heavily on the particular
definition of fine-tuning chosen. We contrast the results of applying such
measures to the constrained MSSM and a semi-constrained NMSSM with those
obtained using so-called naturalness priors. The latter arise automatically
in the context of a Bayesian analysis quantifying the plausibility that a
given model reproduces the weak scale. Consequently, these naturalness priors
have a well-defined probabilistic interpretation, and allow naturalness to
be rigorously grounded in Bayesian statistics. We find that results based
on naturalness priors agree qualitatively with the traditional measures of
fine-tuning used, and illustrate how naturalness priors can provide
valuable insight into the hierarchy problem.
We consider a simplified model of dark matter, taken to be a Majorana fermion, coupling to quarks via colored scalar mediators. The spin independent dark matter-nucleon cross-section vanishes at tree level. In order to calculate direct detection constraints, we calculate, the 1-loop leading order contributions to the spin independent cross-section, also performing RG evolution of the wilson coefficients. Further, we calculate LHC cross-sections at NLO precision and recast LHC searches to determine collider constraints on this model.
We examine the charged lepton flavor violating process $g g \rightarrow \mu \tau$ at the $\sqrt{s} = 13$ TeV LHC. Operators generating this process can be induced by new physics at dimension 8. Despite the power suppression associated with dimension 8 operators, we show that the LHC's large gluon luminosity makes it possible to probe this channel. For an integrated luminosity of 100 fb$^{−1}$ at the LHC, we predict a constraint on the NP scale $\Lambda > 3$ TeV. In addition, we point out that such operators can be induced through top quark loops in models that generate dimension 6 operators of the form $t\bar{t}\, \mu \tau$. We find that the NP scale of these dimension 6 operators can be constrained to be $\Lambda>3.4−4.1$ TeV with 100 fb$^{−1}$ of data.
We investigate various scenarios of fermion mass generation in $SO(5)\times U(1)$ models of gauge-Higgs unification, where the Higgs field is a composite Goldstone boson of a new strong sector. If the top quark is the main driving force of EWSB, the parameters of the $(t,b)_L$ doublet are strongly constrained by Z pole observables. The hierarchical mass ratio between the top and bottom quark implies that the $b_R$ must be strongly composite. While a composite $b_R$ is consistent with current experimental limits, it leads to sizable coupling deviations that can be probed by future accelerators such as ILC. The lepton sector has more freedom in model-building, but the most minimal setup again suggests that right-handed singlets are composite fermions. We consider different quantum number assignments for leptons and study the signatures of the reaction $e^+ e^- \rightarrow l^+l^-$ to distinguish them.
New physics has traditionally been expected in the high-pT region at high-energy collider experiments. If new particles are light and weakly-coupled, however, this focus may be completely misguided: light particles are typically highly concentrated within a few mrad of the beam line, allowing sensitive searches with small detectors, and even extremely weakly-coupled particles may be produced in large numbers there. We propose a new experiment, ForwArd Search ExpeRiment, or FASER, which would be placed downstream of the ATLAS or CMS interaction point in the very forward region and operated concurrently there. As a concrete example of light, weakly-coupled particles, we consider dark photons, dark Higgs bosons, ALPs and sterile neutrinos. We find that even a relatively small and inexpensive cylindrical detector can discover such particles in a large and unprobed region of parameter space.
Renormalization for the Georgi-Machacek model is performed based on the on-shell scheme with the use of the minimal subtraction scheme only for the $hhh$ vertex. We explicitly show the gauge dependence in the counterterms of the scalar mixing parameters in the general $R_\xi$ gauge, and that the dependence can be removed by using the pinch technique in physical scattering processes. We then discuss the possible allowed deviations in these one-loop corrected Higgs couplings from the standard model predictions by scanning model parameters under the constraints of perturbative unitarity and vacuum stability as well as those from experimental data.
Model building within the Randall-Sundrum (RS) framework generally involves placing the Standard Model fields in the bulk. Such fields may possess non-zero values for their associated brane-localized kinetic terms (BLKTs) in addition to possible bulk mass parameters. In this talk we clearly identify the regions of the RS model parameter space where the presence of bulk mass terms and BLKTs yield a setup which is free from both ghost and tachyon instabilities. Such physically acceptable parameter space regions can then be used to construct realistic and phenomenologically viable RS models.
Phase transitions in the early universe can readily create an observable stochastic gravitational wave background. I will argue that such a background necessarily contains anisotropies analogous to those of the cosmic microwave background (CMB) of photons, and that these too may be within reach of proposed gravitational wave detectors. Correlations within the gravitational wave anisotropies and their cross-correlations with the CMB can provide new insights into the mechanism underlying primordial fluctuations, such as multi-field inflation, as well as reveal the existence of non-standard ``hidden sectors" of particle physics in earlier eras.
We have studied the generation of gravitational waves by magnetohydrodynamic turbulence during the Electroweak Phase Transtion (EWPT).
We use direct numerical simulations (DNS) of decaying and forced hydromagnetic turbulence during the EWPT. For that purpose, we use the Pencil Code (https://github.com/pencil-code), an open source code that allows to solve sets of partial differential equations on large, massively parallel platforms.
In previous work we studied the production of primordial magnetic fields during cosmological times to try to explain the coherent magnetic fields that, according to some observations, might be present from the scale of galaxies to clusters of galaxies. We concluded in that work that helical magnetic fields were more suitable to produce the required strengths derived from observations.
We have characterized the perturbations in the metric tensor produced by gravitational waves. We have studied the linear polarization basis components $h_{+,\times}$ and the energy and helical spectra produced by gravitational waves.
We have also studied the temporal evolution of the energy density of gravitational waves and the ratio of GW energy density to the source energy density.
We conduct this analysis for different turbulent sources.
For that purpose, we have developed the gravitational waves module of the Pencil Code. We compute the stress-energy tensor produced by hydromagnetic turbulent sources and then we solve the linearized Einstein field equations.
We have also analyzed the evolution of the gravitational wave energy density with the expansion of the Universe in the context of the Friedmann-Lemaitre-Robertson-Walker model. Then, we have computed the ratio of gravitational wave to critical energy density $\Omega_{\text{GW}}$ and have compared the obtained values with the sensitivity of LISA mission to study the feasibility of detecting traces of primordial magnetic fields in the early Universe gravitational waves and to predict the detectable properties of the gravitational waves polarization spectrum.
Dark matter (DM) that implodes neutron stars (NSs) may explain the paucity of pulsars in the Milky Way galactic center, the source of r-process elements, and the origin of fast-radio bursts. We identify new astrophysical signatures of NS-imploding DM, which could decisively test these hypotheses in the next few years.
The use of distribution of NS mergers in the galaxies, in particular, will allow us to probe DM-nucleon interaction cross-sections 4 to 10 orders of magnitude better than the direct detection experiments in a few-years timescale.
We also propose other direct and indirect phenomena including solar-mass black holes from NS collapse, "Quiet Kilonovae", and "Black Mergers" from the implosions.
This talk is based on arXiv:1706.00001 (PRD 2018)
Observations of gravitational waves from neutron star mergers offer the first access to possible vacuum energy contributions of new QCD phases at large densities. Measurements of this sort have the potential to turn neutron stars into laboratories for fundamental physics: they can provide a new test of the gravitational properties of vacuum energy, and determine the size of the QCD contributions to vacuum energy.
Among cosmological relaxation solutions to the weak-scale hierarchy problem, gauge boson production is a particularly efficient backreaction mechanism for trapping the relaxion. In these models, scanning can even happen after inflation and the relaxion field range can be sub-Planckian, with no extremely small parameters or large e-foldings involved. We consider a model where particle production by the relaxion also reheats the universe and generates the baryonic matter-antimatter asymmetry. Out-of-equilibrium leptons, produced by the relaxion or from the hidden sector, scatter with the thermal bath through interactions that violate CP and lepton number via higher-dimensional operators. Such an effective field theory setup, with no new physics below the cut-off, is sufficient to achieve successful leptogenesis by the relaxion. The baryon asymmetry is thus intrinsically tied to a weak-scale hierarchy.
In this talk, we will discuss how the dimension-six operators change the rate of baryon number violation rate via sphaleron transition. Applying Newton-Kantorovich method, we solve related nonlinear sphaleron equations numerically. Depending on the sign of the coefficients of the dimension-six operators, the sphaleron energy will increases or decreases. Since the coefficient of these dimension-six operators are already constrained by electroweak precision measurement, we can show that they can change the energy of sphaleron energy by a few percent, which doesn't deviate much from the sphaleron energy of standard model.
Quantum fields living on cosmological spacetimes can experience particle production due to their interaction with the expanding background. Given the right conditions, the energy density of the particles produced through this process can become pronounced enough to backreact on the cosmological expansion. In this work we review the basics of cosmological quantum particle production through the lens of asymptotic analysis and discuss the backreaction effects of a quantized scalar field on a cosmological bounce scenario. Finally, we discuss the relevance of quantum particle production for inflationary scenarios.
Inspired by the Contino-Pomarol-Rattazzi mechanism we explore scenarios with a very light (100 keV to 10 GeV) radion which could be associated with the suppression of the electroweak contribution to vacuum energy. We construct explicit, realistic models that realize this mechanism and explore the phenomenological constraints on this class of models. Compared with axion-like particles in this mass range, the bounds from SN 1987a and from cosmology can be much weaker, depending on the the mass of the radion and its coupling to other particles. For example with couplings suppressed by a scale lower than 100 TeV much of the mass window from 100 keV to 10 GeV is still open.
We study novel scenarios where thermal dark matter (DM) can be efficiently captured in the Sun and annihilate into boosted dark matter. In these scenario, viable thermal relic DM with masses O(1)-O(100) GeV. Taking advantage of the energetic proton recoils that arise when the boosted DM scatters off matter, we propose a detection strategy which uses large volume terrestrial detectors, such as those designed to detect neutrinos or proton decays. Constraints and projections are made for the water Cherenkov detectors Super-Kamiokande and Hyper-Kamiokande. Due tot their lower thresholds, better resolution, and more powerful particle identification, current and proposed liquid argon detectors should have enhanced sensitivity in large parts of parameter space. We discuss issues that arise in studying this model at such experiments and present a Monte Carlo tool suitable for the more complex physics that can arise in these detectors.
I will discuss a novel search strategy of light boosted dark matter at WIMP direct detection experiments (particularly in Xenon1T) and ProtoDUNE, prototype of DUNE far detector.
This is based on the scenarios of boosted DM (BDM) composed of the heavy and light DM components where the heavier one interacts with the Standard Model sector only through the lighter one.
The expected signal is energetic recoil of target, possibly with displaced multi-track events if an inelastic scattering occurs.
This is also based on a first proposal of new physics search at ProtoDUNE.
I will show that meter-scale underground experiments such as LUX, PandaX-II, XENON, and PICO could discover dark matter up to the Planck mass and beyond, via new dedicated searches for dark matter scattering multiple times as it transits these detectors. These searches would effectively double the reach of current experiments, and open up significant discovery potential through re-analysis of existing and future data. Amusingly, the mass, cross-section and local density of such dark matter may be pinpointed with a single experiment, using the angle of entry into the detector. I will also identify a hitherto-neglected effect in studies of strongly interacting dark matter, ``saturated overburden scattering", which extends the reach of published limits and future analyses by many orders of magnitude.
Dark matter that is capable of sufficiently heating a local region in a white dwarf will trigger runaway fusion and ignite a type 1a supernova.
We consider dark matter (DM) candidates that heat through the production of high-energy standard model (SM) particles, and show that such particles will efficiently thermalize the white dwarf medium and ignite supernovae.
Based on the existence of long-lived white dwarfs and the observed supernovae rate, we put new constraints on ultra-heavy DM candidates $m_\chi > 10^{16}~\text{GeV}$ which produce SM particles through annihilation, decay, and DM-SM scattering in the stellar medium.
As a concrete example, we rule out supersymmetric Q-ball DM in parameter space complementary to terrestrial bounds.
We put further constraints on DM that is captured by white dwarfs, considering the formation and self-gravitational collapse of a DM core.
For asymmetric DM, such a core may form a black hole that ignites a supernovae via Hawking radiation, and for ``almost asymmetric'' DM with non-zero but sufficiently small annihilation cross section may ignite the star via a burst of annihilation during gravitational collapse.
This constrains much lighter candidates, $m_\chi > 10^{7}~\text{GeV}$.
It is also intriguing that the DM-induced ignition discussed in this work provide an alternative mechanism of triggering supernovae from sub-Chandrasekhar mass progenitors.
We propose a novel method utilizing stellar kinematic data to detect low-mass substructure in the Milky Way’s dark matter halo. By probing characteristic wakes that a passing dark matter subhalo leaves in the phase space distribution of ambient halo stars, we estimate sensitivities down to subhalo masses ∼ 10e7 M_{Sun} or below. The detection of such subhalos would have implications for dark-matter and cosmological models that predict modifications to the halo-mass function at low halo masses. We develop an analytic formalism for describing the perturbed stellar phase-space distributions, and we demonstrate through simulations the ability to detect subhalos using the phase-space model and a likelihood framework. Our method complements existing methods for low-mass subhalo searches, such as searches for gaps in stellar streams, in that we can localize the positions and velocities of the subhalos today.
Macroscopic objects made of baryonic matter with sizable strangeness (i.e. many of the valence
quarks are strange quarks, rather than the usual up and down quarks found in protons and neutrons)
may be stable, and may have formed prior to nucleosynthesis thus evading the principal
constraint on baryonic dark matter. We have analyzed the expected signals that would be produced
from the passage of macroscopic dark matter (macros) through the atmosphere and sedimentary
rock. Fluorescence detectors (FD) such as those of Pierre Auger Observatory and JEM-EUSO
could detect the light produced from the recombination of the resulting plasma in the atmosphere.
This could involve hardware or software changes to the trigger. The tracks of metamorphic rock
(fulgurites) that macros would leave in passing through sedimentary rock could be distinguished
from the surrounding sedimentary rock. We present the regions of parameter space that could be
probed from the expected atmospheric
uorescence and fulgurite tracks.
Dark matter particles traveling through the solar system may scatter off of nuclei in bodies like the Sun and the Earth and become gravitationally trapped. If the dark matter interacts with the Standard Model through a light mediator, the captured dark matter population will annihilate to produce these mediators, and their decays furnish a "smoking gun" signature of dark matter. We examine in detail the case of dark matter interacting through the dark photon portal and find regions of parameter space untouched by current analyses where dark matter may still be discovered by existing experiments.
We investigate the parameter space in which the dark photon may still explain the muon g-2 anomaly. We consider a model of an inelastic dark sector which couples directly to the dark photon. This scenario may lead to semi-visible decays of the dark photon leading to a parameter space in which the dark photon interpretation of the muon g-2 anomaly may still be viable as opposed to both exclusively visible and invisible decays, which have been excluded by experiments. Furthermore, we show that one of the dark sector states may contribute to the required dark matter relic abundance. It is possible that the semi-visible events we discuss, may have been vetoed by experiments searching for the invisible dark photon decays, such as BABAR.
The search for associated production of Higgs bosons and top quark-antiquark pairs is reported, based on a dataset of 35.9 fb$^-1$ collected by the CMS experiment in 2016 in proton-proton collisions at a center-of-mass energy of $\sqrt(s)$ = 13 TeV at the CERN LHC. The search expoits statistically independent analysis targeting different Higgs boson and top quark-anitquark pair decay modes, employing final states with leptons, photons, jets and hadronically decaying $\tau$ leptons. The results from this search are combined with the dataset collected in 2011 and 2012 in proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 and 8~TeV. An excess of events is observed, with a significance of 5.2 standard deviations over the background-only hypotesis, where the corresponding expected significace for a standard model Higgs boson of 125.09 GeV of mass is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26$^{+0.31}_{-0.26}$.
The Higgs couplings to heavy quarks, top and bottom quarks, are difficult to directly access experimentally, nevertheless their measurement is crucial for a full characterization of the Higgs sector and to probe a large variety of physics scenarios beyond the Standard Model. In this talk I will discuss the results recently obtained by the ATLAS Collaboration based on Run-2 2015 and 2016 data, which led to evidence for Higgs boson decays to b-quarks and for the ttH production mode.
This talk reviews recent CMS results on the searches for HH pair production at the LHC, in several Higgs decay channels, both resolved and boosted. Several BSM models predict resonances decaying to HH pairs. Non-resonant HH production is not only sensitive to BSM physics but will also eventually inform our understanding of the shape of the Higgs potential of the standard model.
Measuring the Higgs self-coupling at the LHC has proven to be extremely challenging in the Standard Model, making such a measurement a primary target for future 100 TeV colliders. We explore an alternative scenario, where the LHC is upgraded to 27 TeV — the so-called “High-Energy” (HE)-LHC. We demonstrate the capabilities of such a 27 TeV proton collider at measuring the Higgs self-coupling via di-Higgs production in the $b\bar{b}\gamma\gamma$ channel. Our projections are based on a full simulation of the detector performance using Delphes, based on the current projected performance for the ATLAS detector at HL-LHC, with simulations of all signal and relevant backgrounds. We find that a $5 \sigma$ discovery of di-Higgs production is possible at a 27 TeV collider, which corresponds to a $\sim 40\%$ measurement of the trilinear coupling in the $b\bar{b}\gamma\gamma$ channel alone.
With the discovery of Standard Model (SM) Higgs boson at the LHC, exploring the thermal history associated with electroweak symmetry-breaking (EWSB) has taken on heightened interest. In particular, the process of the electroweak phase transition (EWPT) in early Universe provides conditions able to explain the observed cosmic matter-antimatter asymmetry, if the transition were of first order and sufficiently strong.
The prospects for resonant di-Higgs production searches at LHC in the context of probing the EWPT in Higgs portal extension of the SM will be illustrated. Particular attention will be given to the bbWW channel (with W leptonic decays), where the presence of neutrinos in the final state does not allow the reconstruction of the invariant mass of the heavy scalar. I will present a novel technique [1], called Heavy Mass Estimator (HME), that allows to fully reconstruct the kinematic of the process, and therefore to reconstruct the heavy Higgs invariant mass. We proved that, using the HME technique, this channel can be sensitive as much as bbbb, bbγγ, and bbττ channels, leading to a potential discovery of resonant di-Higgs production with the datasets accumulated in High Luminosity phase of LHC, foreseen in 2035.
[1] https://journals.aps.org/prd/abstract/10.1103/PhysRevD.96.035007
The Twin Higgs mechanism can address the naturalness problem without introducing top partners that are produced at hadron colliders with a large cross section. Only the scalar modes and optionally the twin hypercharge gauge boson, but not the remaining partner particles, have direct couplings to the Standard Model states and are therefore the first modes that can be accessed at colliders. We comment on measurements that can be performed at the LHC and at future colliders in order to test generic predictions arising from the Twin Higgs mechanism.
The critical point for a Higgs sector is here connected to a minimum in the potential for a modulus field. Dynamics of the modulus set the Higgs mass to zero, making Higgs criticality an attractor. An explicit 5-dimensional model for this type of Higgs sector is constructed, where the modulus field is the radion, and Higgs criticality at the minimum of the radion potential is robust under renormalization of the 5D theory due to a sizable critical region in parameter space. In this example, the radion spectrum is gapped, and there are no light particles besides the Higgs, in conflict with expectations from the 4D effective theory, in which the Higgs mass simply looks fine-tuned to zero. The model has an approximately conformal dual where the running of a near-marginal operator drives a scaling dimension towards the complex plane, initiating discrete scale invariance and an instability in the IR, the dual to the AdS tachyon of Breitenlohner and Freedman. The would-be tachyon is stabilized by condensates, terminating the discrete scale invariance precisely at the scale where there is a massless Higgs excitation. There are many parallels to statistical and condensed matter physics models exhibiting so-called "self-organized criticality".
The cancellation of the quadratic divergence and the log divergence lead to general sum rules for the couplings of the top partners. I present these sum rules and explore how to test them at colliders. We can probe this sum rule via the $pp\rightarrow qht{'}$ channel in both Little Higgs Model and Maximally Symmetric Higgs Model. Besides the detection of the $m_{t^{'}}$ and the absolute value of the Yukawa coupling $ht^{'}t^{'}$, the interference gives a chance to detect the sign of the $ht^{'}t^{'}$ coupling.
The observation of neutrino oscillations requires an extension of the Standard Model that generates neutrino masses and mixing. The seesaw mechanism and its various realisations are among the most studied possibilities and one of their most striking phenomenological signature is lepton number violation. We will present a new theorem stating that the requiring the light neutrinos to remain massless to all orders in the perturbative expansion is equivalent to enforcing lepton number conservation. This provides a firm basis in requiring lepton number to be nearly conserved in low-scale seesaw models and proves that any symmetry used to lower the seesaw scale contains lepton number as a subgroup or as an accidental symmetry.
The clockwork framework can generate exponentially small couplings in theories with no input small parameters, and is especially suited to explain the hierarchically small neutrino masses. We consider the phenomenology of a discrete clockwork theory with a Dirac Standard Model neutrino (unlike in seesaw models) and N additional Dirac neutrinos. Exact diagonalisation of the mass matrix with Yukawa couplings to the SM is challenging, and we find analytic solutions for the spectrum and couplings using a large-N expansion. We consider lepton-flavour violation and precision electroweak constraints on this model, and we also discuss the potential of present or future colliders to discover the TeV-scale excited neutrino states predicted by the model.
The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. We propose a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. We show that this structure achieves the goal of filling both the above gaps with couplings of order unity. In this talk, I will briefly describe the model, while the companion talk will discuss leptogenesis from this model in detail.
We propose a hybrid seesaw model that explains the smallness of Majorana mass splitting in inverse seesaw with couplings of order unity and can furthermore achieve successful leptogenesis. Our hybrid seesaw model has distinguishing features compared to the standard high scale type-I seesaw and inverse seesaw. Firstly, it has much richer phenomenology. Indeed, it predicts new TeV scale physics (including scalars) potentially accessible at present and future colliders and may also have astrophysical and cosmological signatures due to the presence of a light Nambu-Goldstone boson coupled to neutrinos. Secondly, our scenario features an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses beyond the usual $∼10^9−10^{15}$ , without large hierarchies in the Yukawa couplings nor small mass splitting among the singlets.
We present simple left-right symmetric theory to calculate heavy Majorana neutrino masses. This model analyzes to generate neutrino masses through two-loop radiative corrections. The model propose the minimal Higgs sector composed of scalar charged singlet and two Higgs doublet instead of scalar triplet.
We propose a new mechanism for neutrino mass generation. In our model, neutrino mass is due to neutrinos coupling to a long range scalar potential, and this potential is sourced by dark matter. This leads to a neutrino mass that depends on local dark matter densities and a repulsive scalar force between neutrinos and dark matter. One prediction of this model is that relic neutrinos are mostly absent from our galactic neighborhood. Our model could thus be falsified by the detection of relic neutrinos at future proposed experiments, such as PTOLEMY.
Important questions in solar neutrinos need to be answered. How? We propose the solar neutrino program for the next-generation neutrino experiment--DUNE. We first show the advantages of DUNE itself. Then we show that the detection backgrounds can be made low to make this program realistic. From our analysis, DUNE solar program could give the best measurement of mixing parameters and $^{8}B$ flux, and make the first detection of $hep$. The spectacular results DUNE would achieve may open substantial discovery space in particle physics and astrophysics.
Detection of the diffuse supernova neutrino background (DSNB) is of great importance, which will greatly help the understanding of both core-collapse (including supernova) physics and neutrino physics. However, after tens of years' effort of Super-Kamiokande (SK), DSNB is still hidden in the remaining backgrounds, dominated by atmospheric neutrinos.
In this work we study the underlying physics of the atmospheric neutrino interactions in SK and propose new detection methods for DSNB detection, for both current SK and future SK-Gd, which has the neutron-tagging ability. These methods, if adopted by SK, will greatly improve the detectability of DSNB.
I give a lightning tour of recent developments in CTEQ-TEA parton distribution functions (PDFs) and of a new program PDFSense for visualization of experimental constraints on the PDFs. The PDFSense tool allows a user to identify and plot individual measurements in the CTEQ-TEA analysis constraining the PDF dependence of a QCD observable of interest, such as a precision electroweak or new-physics cross section at the LHC. With the help of PDFSense, many physics insights about the PDFs can be gained or reinforced. As one of many examples, it is employed to rank the projected impact of new LHC measurements in jet, vector boson, and ttbar cross sections on the PDFs, and to evaluate the potential of future deep-inelastic scattering experiments for constraining the nucleon structure.
We calculate the soft function for the global event variable 1-jettiness at next-to-next-to-leading order (NNLO) in QCD. We focus specifically on the non-Abelian contribution, which, unlike the Abelian part, is not determined by the next-to leading order result. The calculation uses the known general forms for the emission of one and two soft partons and is performed using a sector-decomposition method that is spelled out in detail. Results are presented in the form of numerical fits to the 1-jettiness soft function for LHC kinematics (as a function of the angle between the incoming beams and the final-state jet) and for generic kinematics (as a function of three independent angles). These fits represent one of the needed ingredients for NNLO calculations that use the N-jettiness event variable to handle infrared singularities.
The LHC's high-luminosity upgrade will create intense pileup, which motivates a more global, correlation-based approach to collider event reconstruction. The QCD power spectrum encodes the total event shape at large and small angles. Jets and their substructure can then be extracted from this power spectrum. A useful feature of this approach is the absence of a jet radius parameter, so that narrow and fat jets can be fit simultaneously. And instead of a local pileup subtraction, the global fit allows pileup to be treated as a cohesive entity. This produces a reconstruction which is robust to extremely high pileup.
Processes where at least one photon or one jet produced in a proton-proton collision are measured with the ATLAS detector. The results of the measurements are used to test QCD predictions in several phase-space regions.
We study Heavy quark jet fragmenting processes. When heavy quarks are involved in a jet, the quark mass can give a large impact on the jet cross section and its substructures. With this motivation, at next-to-leading order in $\alpha_s$ we calculated the heavy quark mass effects on the fragmentation functions to a jet (FFJs) and the jet fragmentation functions (JFFs), where the former describes fragmentation of parton into a jet and the latter describes fragmenting processes inside a jet. The finite size of the heavy quark mass does not change the ultraviolet behaviors, but it can give significant corrections to the finite contributions. Also when we take the zero mass limit, we find that the FFJs and the JFFs reproduce established results for massless partons. When we define the heavy quark jet as one to include at least one hone (anti-)heavy quark, the tagged heavy quark jet production is sensitive to the heavy quark mass and produces large logarithms related to the quark mass as known. Taking advantage of the FFJs and JFFs we formulate the factorization theorem on the heavy quark jet production in order to resum the large logarithms systematically. As an application, we study the inclusive $b$-jet production and show useful phenomenological results.
We update our eikonal fit and comprehensive fits to high energy data on proton--proton and antiproton--proton forward scattering for $\sigma$, $\rho$, and $B$ including the Telescope Array value of total proton-proton cross section at $W=\sqrt{s}$ = 95 TeV and the latest measurements of the inelastic cross sections at $W$= 8 TeV (by TOTEM and ATLAS) and 13 TeV (by CMS and ATLAS). The stability of the fits is excellent and the obtained results agree well with the predictions of earlier fits. This work again confirms the evidence for the proton asymptotically becoming a black disk of gluons.
Higgs exclusive decay to a J/Psi plus a photon is a clean channel to probe the Higgs-charm coupling. In this process, large logarithms log(m_c/m_H) are resummed using the evolution of the lightcone distribution amplitude (LCDA), which in turn is matched to the long-distance matrix elements in NRQCD at the scale m_c. We will demonstrate the matching to O(v^4) and its phenomenological implications.
We estimate the rate of the Cabibbo-favored weak decay, $\Lambda_c^+ \rightarrow \Lambda_s^0~ \pi^+$, using QCD Sum Rules. A three-point correlation function of field operators corresponding to charmed lambda ($\Lambda_c^+$), strange lambda ($\Lambda_s^0$), and weak Hamiltonian ($H_W$) is considered in the presence of an external pion field. We evaluate the lowest-order perturbative diagram in which the charm quark decays into the strange quark via a weak-charged current. A dispersion relation is used for the correlator obtained from the OPE, and a Borel transform is carried out to ensure rapid convergence. After comparing the decay rate for this process to the strong decay mode, $\Lambda_c^+ \rightarrow p K^- \pi^+$, we find this weak decay to be small and consistent with experimental observations.
We consider a feeble long range scalar force that mainly couples to dark matter and unstable Standard Model states, like the $\mu$. The induced background scalar field depends on dark matter number density, causing the mass of the unstable particles to have spatial and temporal variations. These variations would leave an imprint on the value of the fine structure constant $\alpha$. This mechanism can accommodate the mild preference of the Planck data for such a deviation, $(\alpha_{\rm CMB} − \alpha_{\rm present} )/\alpha_{\rm present} = (−3.6 \pm 3.7) \times 10^{−3}$. In this case, the requisite parameters typically imply that violations of the Equivalence Principle are not far beyond current limits.
Future measurements of primordial non-Gaussianity (NG) can reveal cosmologically produced particles with masses of order the inflationary Hubble scale, which can be as high as $\sim 10^{14}$ GeV. I will describe how (partially) Higgsed gauge theories, naturally having particles with Hubble scale masses, can leave observable signatures in future NG measurements giving us a chance to do spectroscopy of masses and spins of such particles. In particular, a “heavy-lifting” mechanism will be analyzed in which couplings to curvature can result in Higgs scales of order the Hubble scale during inflation while reducing to far lower scales in the current era, where they may now be accessible to collider and other laboratory experiments. Such a mechanism is testable in the sense that renormalization-group running of terrestrial measurements can yield predictions for cosmological NG.
The Standard Model Higgs boson, which has previously been shown to develop an effective vacuum expectation value during inflation, can give rise to large particle masses during inflation and reheating, leading to temporary blocking of the reheating process and a lower reheat temperature after inflation. We study the effects on the multiple stages of reheating: resonant particle production (preheating) as well as perturbative decays from coherent oscillations of the inflaton field. Specifically, we study both the cases of the inflaton coupling to Standard Model fermions through Yukawa interactions as well as to Abelian gauge fields through a Chern-Simons term. We find that, in the case of perturbative inflaton decay to SM fermions, reheating can be delayed due to Higgs blocking and the reheat temperature can decrease by up to an order of magnitude. In the case of gauge-reheating, Higgs-generated masses of the gauge fields can suppress preheating even for large inflaton-gauge couplings. In extreme cases, preheating can be shut down completely and must be substituted by perturbative decay as the dominant reheating channel. Finally, we discuss the distribution of reheat temperatures in different Hubble patches, arising from the stochastic nature of the Higgs VEV during inflation and its implications for the generation of both adiabatic and isocurvature fluctuations.
In this talk I will present some original work in which we suggest that the relic density of dark matter may be produced thermally in a hidden sector whose interaction with the standard model is exclusively passing through the inflationary sector. I will show that the parameter space required for such an inflaton portal is extremely natural as compared to previous proposals on highly decoupled dark matter production and can be probed by high energy cosmic ray searches.
Recently the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) reported the detection of a 21cm absorption signal stronger than astrophysical expectations. The radiation from dark matter (DM) decay and primordial black holes (PBH) injects energy into the intergalactic medium, which can heat up neutral hydrogen gas and weaken the 21cm absorption signal imposing constraints. Injection models considered are decay channels DM$\rightarrow \gamma\gamma$, e^+e^-, $\mu^+\mu^-$, $\tau^+\tau^-$, $b\bar{b}$ and the $10^{15-17}$g mass range for primordial black holes, and it is also required that the heating of the neutral hydrogen does not negate the 21cm absorption signal. For $e^+e^-$, $\gamma\gamma$ final states and PBH cases, strong 21cm bounds are found that can be more stringent than the current extragalactic diffuse photon bounds. For $b\bar{b}$ and $\mu^+\mu^-$ cases, the 21cm constraint is better than all the existing constraints for $m_{\rm DM}<30$ GeV. For both DM decay and primordial black hole cases, the 21cm bounds significantly improve over the CMB damping limits from Planck data.
Future neutron-antineutron ($n$-$\bar n$) oscillation experiments, such as at the European Spallation Source (ESS), aim to find first evidence of baryon number violation. We investigate implications of an improved $n$-$\bar n$ oscillation search for baryogenesis via interactions of $n$-$\bar n$ mediators, parameterized by an effective field theory (EFT). We find first and foremost that even in a minimal EFT setup, there is substantial overlap between the parameter space probed by the ESS and the region that can realize the observed baryon asymmetry of the universe. We further find that the mass scales of exotic new particles can be significantly higher than what could be detected at the LHC or its envisioned upgrades. Given the innumerable high energy theories that can match to, or resemble, the lower energy minimal EFT that we discuss, future $n$-$\bar n$ oscillation experiments could have substantial impact on many viable theories of baryogenesis beyond what other experiments can probe.
Sub-MeV dark matter remains unconstrained by direct detection, and there are several well-motivated candidates in this mass range. Electron recoil experiments have been proposed as a technique to detect such a light particle, but little is known about the extent of cosmological restrictions on a generic light species coupled to electrons. We study cosmological constraints on a light dark matter particle coupled to electrons in the framework of an effective field theory, which subsumes a broad class of models with a heavy mediator. We study constraints from primordial nucleosynthesis, the dark matter relic abundance, and the effective number of neutrino species ($N_{\mathrm{eff}}$) at CMB formation. We demonstrate the implications of our results for detection prospects in electron recoil experiments, and highlight the regions of parameter space which may be amenable to direct detection by such techniques.
We have studied the statistical properties and the associated realizability condition for helical primordial magnetic fields. These have been related to the smoothed magnetic fields generally used to constrain the fields from observational data. In particular, we have looked at fields generated during inflation which have a scale-invariant spectrum. We have determined the relation between the correlation length of these fields and the low-$k$ cutoff of the perturbations during inflation. It is shown that the observational signatures on the CMB due to these inflationary fields depend on this scale. We have also numerically studied how the $k^{-1}$ spectral shape changes over time with turbulent evolution.
Based On:
Axel Brandenburg, Ruth Durrer, Tina Kahniashvili, Sayan Mandal, Weichen Winston Yin, "Statistical Properties of Scale-Invariant Helical Magnetic Fields and Applications to Cosmology", arXiv:1804.01177.
Axel Brandenburg, Tina Kahniashvili, Sayan Mandal, Alberto Roper Pol, Alexander G. Tevzadze, Tanmay Vachaspati, "Evolution of hydromagnetic turbulence from the electroweak phase transition", Phys.Rev. D96 (2017) no.12, 123528.
Axel Brandenburg, Tina Kahniashvili, Sayan Mandal, Alberto Roper Pol, Alexander G. Tevzadze, Tanmay Vachaspati, "The dynamo effect in decaying helical turbulence", arXiv:1710.01628.
In the Dynamical Dark Matter (DDM) framework, the dark sector comprises a large number of constituent particles whose individual masses, lifetimes, and cosmological abundances scale with respect to each other in specific ways. Thus far, DDM model-building has primarily relied on non-thermal mechanisms for abundance generation such as misalignment production, since these mechanisms give rise to appropriate scaling relations between these quantities. In this talk, I will show that an appropriate set of scaling relations for DDM can also arise from thermal freeze-out. Moreover, I shall show that a far broader range of viable scaling relations between dark-matter lifetimes, abundances, and masses can be achieved in thermal DDM scenarios than in the non-thermal scenarios for DDM that have previously been considered. Thus, the extension of the DDM framework into the thermal domain opens up a rich array of new phenomenological possibilities for DDM — possibilities that can be readily probed by canonical detection methods for MeV- to TeV-scale dark-matter candidates.
I will discuss the possibility of bremsstrahlung of a photon or dark sector particle being the leading order process for the direct detection of dark matter within the effective field theory framework. It will be shown under what circumstances a bremsstrahlung process could possibly alleviate momentum suppression or spin-dependence of the interactions.
We present Self-Destructing Dark Matter (SDDM), a new class of dark matter models which are detectable in large neutrino detectors. In this class of models, a component of dark matter can transition from a long-lived state to a short-lived one by scattering off of a nucleus or an electron in the Earth. The short-lived state then decays to Standard Model particles, generating a dark matter signal with a visible energy of order the dark matter mass rather than just its recoil. This leads to striking signals in large detectors with high energy thresholds. We present a few examples of models which exhibit self destruction, all inspired by bound state dynamics in the Standard Model. The models under consideration exhibit a rich phenomenology, possibly featuring events with one, two, or even three lepton pairs, each with a fixed invariant mass and a fixed energy, as well as non-trivial directional distributions. This motivates dedicated searches for dark matter in large underground detectors such as Super-K, Borexino, SNO+, and DUNE.
Cannibals are dark matter particles with a scattering process that allows three particles to annihilate to two. This exothermic process keeps the gas of the remaining particles warm long after they become non-relativistic. A cannibalizing dark sector which is decoupled from the Standard Model naturally arises from a pure-glue confining hidden sector. It has an effective field theory description with a single massive interacting real scalar field, the lightest glueball. Since warm dark matter strongly suppresses growth of structure cannibals cannot be all of the dark matter.
In this talk I propose a scenario where most dark matter is non-interacting and cold but about 1 percent is cannibalistic. I review the cannibals' unusual scaling of the temperature and energy and number densities with redshift and generalize the equations for the growth of matter density perturbations to the case of cannibals. I solve the equations numerically to predict the scaling of the Hubble parameter and the characteristic shape of the linear matter power spectrum as a function of model parameters. The results may have implications for the $\sigma_8$ and $H_0$ problems.
This talk is based on the paper arXiv:1803.08062.
We perform a combined likelihood analysis for IceCube 6-year High-Energy Starting Events (HESE) and 8-year throughgoing muon events using a two-component neutrino flux model. This can be motivated either from purely astrophysical sources or due to a beyond Standard Model contribution, such as decaying heavy dark matter. We find that the astrophysical plus dark matter interpretation is mildly preferred by the current data over the purely astrophysical explanation. As for the astrophysical neutrinos, we consider two different source flavor compositions, corresponding to the standard pion decay and muon-damped pion decay sources. We find that the latter is slightly preferred over the former as the high-energy component, while the low-energy component does not show any preference. We also take into account the multi-messenger gamma-ray constraints and find that our two-component fit is compatible with these constraints, whereas the single-component power-law bestfit to the HESE data is clearly ruled out.
The clockwork mechanism is a powerful technique to "naturally" generate
exponentially small couplings. One of the physical instances where we require exponentially small couplings are in a freeze-in scenarios of dark matter. I will
discuss the phenomenology of freeze-in dark matter and how the clockwork mechanism
can be used to generate viable freeze-in models.
The mechanism of “spontaneous leptogenesis” — in which the matter-antimatter asymmetry is generated via motion of a scalar field coupled to the electroweak gauge bosons — provides an interesting alternative to more traditional thermal leptogenesis models. While an axion-like field is a natural candidate for these models, the observed asymmetry requires an axion mass so large it decays shortly after leptogenesis. In this talk, we demonstrate how effective axion potentials that arise from continuum clockwork models can yield simultaneously sufficient production of baryon asymmetry, and a stable dark matter candidate with the appropriate abundance. Moreover, we find non-trivial dynamics early in the axion field evolution which exhibit a “tracking” behavior — similar to that found in quintessence models — where the axion follows a radiation-like equation of state before undergoing coherent oscillations. As a result of these dynamics, axion-photon isocurvature perturbations are generically suppressed, thereby enlarging the viable parameter space for our model.
The properties of the dark matters, massive graviton and galaxy clusters are discussed in terms of the new three-dimensional quantized space model. Three new particles (bastons) with the electric charges (EC) are proposed as the dark matters [1]. And the rest mass of 1.4 TeV/c2 is assigned to the Le particle with the EC charge of -2e based on the data of DAMP (Dark Matter Particle Explorer) [1]. The 3.5 and 74.9 keV X-ray peaks observed from the cosmic X-ray background spectra support the presence of the Q1 quark with the EC of -4e/3. The rest mass and force range of the massive g(0,0,0) graviton with the Planck size are mg=3.1872 10-31 eV/c2 and xr = 3.0955 1023 m = 10.0 Mpc, respectively, based on the experimental rest mass and rms charge radius of the proton [1]. The possible diameter (10 Mpc) of the largest galaxy cluster is remarkably consistent with the gravitational force range (10 Mpc). Then, the diameter of the largest dark matter distribution related to the largest galaxy cluster is 9.2865 1023 m = 30 Mpc equal to the force range of the massive g(0) graviton with the rest mass of 1.0624 10-31 eV/c2. The reason why the gravitational force between matters is very weak when compared with other forces is explained by the graviton evaporation and photon confinement. Because of the huge number (N) of the evaporated gravitons into the x1x2x3 space, it is concluded that the gravitational force between dark matters should be much stronger than the gravitational force between the matters and the repulsive electromagnetic force between dark matters [1]. The proposed weak gravitational force between the dark matters and normal matters explains the observed dark matter distributions of the bullet cluster, Abell 1689 cluster and Abell 520 cluster. The transition from the galaxy without the dark matters to the galaxy with the dark matters are explained. Also, the accelerated space expansion is caused by the new space quanta created by the evaporated gravitons into the x1x2x3 space and repulsive electromagnetic force between dark matters corresponding to the dark energy. And the space evolution can be described by using these graviton evaporation and repulsive electromagnetic force, too. And three dark matters, three heavy leptons and three heavy quarks which are proposed in the present work [1] need to be confirmed from the high energy cosmic ray and cosmic gamma ray measurements of the high energy astrophysics.
[1] J.K. Hwang, http://meetings.aps.org/Meeting/APR18/Session/G09.6 (talk at 2018 APS April meeting).
I shall discuss the decays of the Higgs boson into lepton pairs in the left-right symmetric model. $h \rightarrow ee, e\mu, e\tau, \mu\tau$ decays will be shown to be in the observable range. There is an intricate connection of these decays with the structure of the neutrino mass, which will be outlined.
Recent years have seen a plethora of indications of deviations from the SM. Most notables among these are LUV in charge as well as in neutral current processes, in the muon (g – 2) and last but not least in the direct CP violation parameter (eps’). In this talk three issues regarding these anomalies will be discussed. First a careful critique and reservation of the status of each anomaly will be discussed. Second, model independent implications wherever possible will be offered. Lastly assuming the anomalies will survive further scrutiny, a theoretically attractive set up that addresses these concerns will be discussed.
Some well-motivated neutrino mass models predict the existence of leptophilic doubly-charged scalars. Their Yukawa couplings can be constrained by low-energy lepton flavor violation and neutrinoless double beta decay searches, as well as by multi-lepton searches at colliders. However, there is still a large chunk of unexplored parameter space, which could be effectively probed by the displaced vertex searches at the LHC and future colliders, as well as the high-precision low-energy experiments like Moller. We show that there exists a novel complementarity between these high-energy and high-precision experiments in probing the origin of neutrino mass.
We examine the cosmological constraints on models in which the Standard Model Higgs Yukawa couplings depend on a new scalar field, the so-called flavon. Production of flavons and their subsequent decay in the early universe pose two threats to standard cosmology: they may spoil the successful predictions from primordial nucleosynthesis (BBN), or they may dilute the primordial baryon asymmetry to an unacceptable level. Though our explicit calculations are performed in the specific framework of Froggatt–Nielsen models, the constraints we derive apply to a much broader range of frameworks in which the Yukawa interactions are determined by the expectation value of a scalar field.
The magnetic moment of a quantum mechanical particle with an angular momentum differs from that of a classical mechanical particle by a factor called the g-factor. For Dirac particles such as electrons, muons, etc., the Dirac theory predicts the g-factor to be 2. There are slight variations from g=2 for these particles because of quantum fluctuations. The anomaly is characterized by the anomalous magnetic moment, $a = \frac{g-2}{2}$. The anomalous magnetic moments for both the electron and the muon have been calculated theoretically and measured experimentally with very high precision. The measurement of the anomalous magnetic moment of the electron agrees very well with the theory predictions. Unlike that of the electron, the anomalous magnetic moment of the muon ($a_\mu$) is more sensitive to heavier physics because of its heavier mass. This also makes $a_\mu$ more sensitive to physics beyond the Standard Model. The most precise measurement of $a_\mu$ so far is made by the E821 experiment at the Brookhaven National Laboratory and the result disagrees with the theory by 3.5 standard deviations. To better understand the deviation, both theoretical and experimental values need to be obtained with higher precision.
The Muon g-2 experiment at Fermilab aims to measure $a_\mu$ to a precision of 140 parts per billion (ppb), which is four times better precision than the E821 experiment. The E821 magnet has been relocated for this experiment and the magnetic field uniformity has been improved threefold by shimming. A completely new set of instruments have been designed, built and installed. The beamline for the experiment has been built and it is designed to give a much higher muon storage fraction. The experiment has begun its first Physics Run in the beginning of FY2018. An overview of the experiment and the current status will be presented.
We analyze prospects for probing A × V parity-odd interactions of muons with quarks, $G(\bar \mu \gamma_\alpha \gamma_5 \mu)(\bar q\gamma^\alpha q)$, using the muon beam experiments at low and medium energy. While this operator is readily induced in the SM by Z-exchange, exotic models with sub-weak scale force mediator (Z$’$) can have an enhancement of this operator by up to two orders of magnitude, G ∼ (1−100)×G$_F$ . The P-odd scattering asymmetry can be accessed experimentally if there is a way of rotating muon spin polarization. Flipping of the muon spin is possible for the two muon beam experiments measuring muon g − 2 at FNAL and JPARC, and we estimate the statistical errors on the asymmetry that can be achieved with current muon intensities. We find that the JPARC experiment will be able to probe the size of the parity violation that is $O(10)$ times larger than the SM prediction, while the FNAL setup would in principle be able to explore all the interesting range of G and eventually detect SM P-odd forces.
Many new physics scenarios beyond the Standard Model often necessitate the existence of a (light) neutral scalar $H$, which might couple to the charged leptons in a flavor violating way, while evading all existing constraints. Such scalars could be effectively produced at future lepton colliders like CEPC, ILC, FCC-ee and CLIC, either on-shell or off-shell, and induce lepton flavor violating signals. We find that a large parameter space of the scalar mass and the lepton flavor violating couplings can be probed, well beyond the current low-energy constraints. The neutral scalar explanation of the muon g-2 anomaly could also be directly tested at future lepton colliders.
In this work we propose a new renormalizable SU(5)-GUT model which explains the origin of neutrino mass via a two-loop neutrino mass mechanism. We construct a viable model where gauge coupling unification is realized that simultaneously satisfies the proton decay constraints. In addition to correctly reproducing the Standard Model charged fermion masses and mixings, in this renormalizable model neutrino mass is generated at the quantum level, hence explains the extremely small neutrino masses. Explaining the experimentally observed neutrino oscillation data requires some beyond Standard Model particles present at the TeV scale. This model has the potential to be tested experimentally by measuring the proton decay in future experiments.
The existence of high-mass neutral or charged Higgs bosons is predicted in a number of theories beyond the Standard Model. The latest results on searches for such particles with the ATLAS detector will be presented.
We present a simple twist in the well studied two Higgs doublet model in the form of an extra interchange symmetry between the two Higgs doublets ($\Phi_1$ $\leftrightarrow$ $\Phi_2$). There is a residual $Z_2$ symmetry that remains unbroken after the original symmetry $\Phi_1$ $\leftrightarrow$ $\Phi_2$ is spontaneously broken. This unbroken $Z_2$ symmetry makes the charged scalars $H^\pm$, the neutral scalar $H$ and the pseudoscalar $A$ to have $Z_2$ negative charges and all the other fields remain $Z_2$ positive. This, in turn, makes the lightest $Z_2$ negative particle, the neutral scalar $H$ to be the candidate for Dark Matter. This neutral scalar $H$ can be much lighter in mass in comparison to the Standard Model-(SM) like neutral scalar $h$ having mass $m_h \simeq 125$ GeV as seen by the LHC. Interestingly this lighter neutral scalar $H$, as well as the charged scalars $H^\pm$ and the pseudoscalar $A$, do not couple to fermions. The lighter neutral scalars also don't have the usual three-point couplings with the Gauge bosons($W^\pm$ and $Z$) present in the Standard Model, but only have four-point couplings with $W^\pm$ and $Z$. As the neutral scalars $h$ and $H$ have interactions among them, the only way to produce the lightest $Z_2$ negative DM candidate $H$ will be through the decays of the SM-like neutral scalar $h$ where this SM-like neutral scalar $h$ will have an extra invisible decay channel through $h \rightarrow H H$. Taking the Invisible decay branching ratio of the $125$ GeV SM-like Higgs can be as large as ${Br_{inv}}_h < 25 \%$, we have studied the parameter space of the effective coupling $\lambda^*$ between the neutral scalars ($hHH$) and the mass of the DM candidate lighter neutral scalar $m_H$. We also comment on the other possible phenomenology for the charged scalars $H^\pm$ and pseudoscalar $A$.
We explore 2 Higgs Doublet models with non-standard flavor structures. In analogy to the four,
well studied models with natural flavor conservation (type 1, type 2, lepton-specific, flipped), we
identify four models that preserve an approximate SU (2) 5 flavor symmetry acting on the first two
generations. In all four models, the couplings of the 125 GeV Higgs are modified in characteristic
flavor non-universal ways. Also the heavy neutral and charged Higgs bosons show an interesting
non-standard phenomenology. We discuss their production and decay modes and identify the most
sensitive search channels at the LHC. We also study the effects on low energy flavor violating
processes. We find relevant constraints from B s meson oscillations and from the rare decay
B s →μ + μ − . Lepton flavor violating B meson decays like B s → τ μ and B → K (∗) τ μ can have branching ratios at an observable level.
We study the prospective sensitivity to CP-violating Two Higgs Doublet Models from the 14 TeV
LHC and future electric dipole moment (EDM) experiments. We concentrate on the search for a
resonant heavy Higgs that decays to a Z boson and a SM-like Higgs h, leading to the Z(ll)h(bb̄)
final state. The prospective LHC reach is analyzed using the Boosted Decision Tree method. We
illustrate the complementarity between the LHC and low energy EDM measurements and study the
dependence of the physics reach on the degree of deviation from the alignment limit. In all cases,
we find that there exists a large part of parameter space that is sensitive to both EDMs and LHC
searches.
We show that within the two Higgs doublet model (T2HDM), where both Higgs doublet couple to fermions in same hierarchical pattern, there can be significant deviations in the Higgs-fermion couplings with respect to their respective standard model values, consistent with flavor constraints and known properties of the Higgs boson. The model is very predictive, implying unavoidable new physics signals like di-boson resonances ($hh$ and $Zh$) from novel decays of $\textit{CP}-$ even and $\textit{CP}-$ odd Higgs fields at the Large Hadron Collider (LHC) and that may lead to an explanation of some intriguing di-boson signatures ($Zh$ excess at 440 GeV and $hh$ resonance at 280 GeV) observed at the ATLAS experiment.
After Higgs discovery, the detail structure of Higgs sector remains to be determined. A well motivated extension of the Standard Model Higgs sector is Two Higgs Doublet Model (2HDM), which predicts a pair of charged Higgs boson $H^{\pm}$, a CP-odd Higgs $A$ and another CP-even Higgs $H$. The conventional searches focus on Higgs decays into a pair of SM fermions or gauge bosons. However, hierarchical 2HDM has exotic Higgs decays, like a heavy Higgs decays to a light Higgs plus vector boson, which reduces the reach of conventional search strategies, while offers alternative discovery channels. Sizable mass splitting, unitarity and vacuum stability require the mass of new scalar particles below 2 TeV. Thus a 100 TeV collider could probe entire hierarchical 2HDM parameter space. In this talk, we present an overview of non-SM heavy Higgs reach via exotic Higgs decays at a future 100 TeV collider.
An enhanced production of double Higgs bosons or exotic decays of the Higgs boson would be two clear signs of beyond Standard Model physics. A search is performed for resonant and non-resonant Higgs boson pair production, where the two Higgs bosons decay to four bottom quarks. Another search is conducted for a Higgs boson decay to XX to four leptons. Both analyses use up to 36 fb$^{−1}$ of p-p collision data collected by the ATLAS detector at 13 TeV. No significant excess is found. The observed 95% confidence level upper limit on the non-resonant Higgs boson pair production is 13 times the Standard Model prediction.
We adopt a general two Higgs doublet model (2HDM) to study the signature
of flavor changing neutral Higgs (FCNH) decays into leptons at the CERN
Large Hadron Collider (LHC) as well as future hadron colliders.
$pp \to \phi^0 \to \tau^\mp\mu^\pm +X$, where $\phi^0$ could be a CP-even scalar [$h^0$ (lighter), $H^0$ (heavier)] or a CP-odd pseudoscalar ($A^0$).The LHC measurements of the light Higgs boson ($h^0$) favor the alignment limit of a 2HDM, in which the couplings of $h^0$ approach Standard Model values.In this limit, FCNH couplings of the light Higgs boson $h^0$ are naturally suppressed by a small mixing parameter $\cos(\beta-\alpha)$, while the FCNH couplings of heavier neutral Higgs bosons $H^0, A^0$
are sustained by $\sin(\beta-\alpha) \sim 1$. We evaluate the production rate of physics background from dominant processes ($\tau^+\tau^-, WW, ZZ, Wq, Wg, t\bar{t}$) with realistic acceptance cuts and tagging efficiencies. Promising results are found for the LHC at 13 or 14 TeV collision energies.
In addition, we study the discovery poential of future pp colliders
with 27 TeV and 100 TeV.
We update the analysis of the pair production of electroweak gauge bosons
taking into account not only the dimension-six operators contributing
to triple gauge boson couplings, but also the modifications to the
couplings of gauge bosons to fermions. We quantify the effect on the LHC bounds on "bosonic" operator coefficients allowed within the present constraints of EWPD on the "fermionic" operator coefficients.
Measurements of the cross sections of the production of two and three electroweak gauge bosons at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a model-independent means to search for new physics at the TeV scale. The ATLAS collaboration has performed measurements of integrated and differential cross sections of the production of heavy di-boson pairs at centre-of-mass energies of 13 TeV. We present in particular measurements of WW, WZ and ZZ cross sections in leptonic decays. In addition, the ATLAS collaboration has searched for the production of three W bosons or of a W boson and a photon together with a Z or W boson at a center of mass energy of 8 TeV. Moreover, results on electroweak production in vector boson scattering of two W bosons of same-sign at center of mass energy of 8 TeV are presented. Results are compared to state-of-the art theory predictions and interpreted in the framework of anomalous gauge couplings.
Vector bosons are readily produced in the pp collisions at the LHC. Measurements of vector boson production cross sections is an important aspect of the ATLAS physics program and deviations of these measurements from the standard model predictions can be used to search for new physics. A selection of Run 2 results with $\sqrt{s} = 13\ \mathrm{TeV}$ data will be presented.
As part of its ongoing exploration into the nature of the particles produced in high energy proton-proton collisions, the ATLAS detector has been used to perform a number of new precision electroweak measurements. In this talk the recent measurements of the W-boson mass, the Drell-Yan triple-differential cross-section and the polarisation of tau leptons in Z/γ* → ττ decays will be discussed.
The study of the associated production of vector bosons and jets constitutes an excellent testbench to check numerous QCD predictions. Total and differential cross sections of vector bosons produced in association with jets has been studied at both 8 and 13 TeV center-of-mass energies. Differential distributions as function of a broad range of kinematical observables are measured and compared with theoretical predictions. Final states with a vector boson and jets can be also used to study electroweak initiated processes, such as the vector boson fusion production of a Z or W boson that are accompanied by a pair of energetic jets having large invariant mass
High precision data of lepton angular distributions for $\gamma^*/Z$ production in $p-p$ collision at LHC, covering broad ranges of dilepton's transverse momentum ($q_T$) and rapidity were reported recently. Strong $q_T$ dependencies were observed for several angular distribution coefficients, $A_i$, including $A_0 - A_4$. Significant rapidity dependencies were also found for the coefficients $A_1$, $A_3$ and $A_4$, while $A_0$ and $A_2$ exhibit very weak rapidity dependence. Using an intuitive approach we show that the $q_T$ and rapidity dependencies of the angular distributions coefficents can be well described. Implications on other hard processes will also be discussed.
Minimal Universal Extra Dimensions (mUED) is an attractive model for physics beyond the Standard Model. It can however only be used as an effective theory valid up to an a priori unknown cutoff scale at which some UV completion takes over.
It is illuminating for that framework to quantify the sensitivity of observables to variations of the cutoff scale - we therefore compare the one loop QCD Vertex functions as they appear in mUED, calculated in different approaches.
Firstly, we perform an analytical summation over all KK modes running in the loops in the 4D effective theory, then an asymptotic expansion in the cutoff scale and finally we extract the vertex functions from the exact functional renormalization group equation, formulated in 5D.
We introduce a new jet clustering algorithm (SIFT: Scale-Invariant Filter Tree), which does not impose a fixed cone size or associated scale on the event. The proposed construction maintains excellent object discrimination for very collimated partonic systems, while asymptotically recovering favorable behaviors of the standard anti-KT algorithm. It is intrinsically suitable (without secondary declustering) for the tagging of highly boosted objects, and applicable to the study of jet substructure. Additionally, it is resilient to pileup, via a concurrent filter on soft wide-angle radiation applied within the primary clustering phase.
In supersymmetric models with scalar sequestering, superconformal strong dynamics in the hidden sector suppresses the low-energy couplings of mass dimension two, compared to the squares of the dimension one parameters. Taking into account restrictions on the anomalous dimensions in superconformal theories, I point out that the interplay between the hidden and visible sector renormalizations gives rise to quasi-fixed point running for the supersymmetric Standard Model squared mass parameters, rather than driving them to 0. The extent to which this dynamics can ameliorate the little hierarchy problem in supersymmetry is studied. Models of this type in which the gaugino masses do not unify are arguably more natural, and are certainly more likely to be accessible, eventually, to the Large Hadron Collider.
We present a model wherein the Higgs mass is protected from the quadratic one-loop top quark corrections by scalar particles that are complete singlets under the Standard Model (SM) gauge group. While bearing some similarity to Folded Supersymmetry, the construction is purely four dimensional and enjoys more parametric freedom, allowing electroweak symmetry breaking to occur easily. The cancelation of the top loop quadratic divergence is ensured by a $Z_3$ symmetry that relates the SM top sector and two hidden top sectors, each charged under its own hidden color group. In addition to the singlet scalars, the hidden sectors contain electroweak-charged supermultiplets below the TeV scale, which provide the main access to this model at colliders. The phenomenology presents both differences and similarities with respect to other realizations of neutral naturalness. Generally, the glueballs of hidden color have longer decay lengths. The production of hidden sector particles results in quirk or squirk bound states, which later annihilate. We survey the possible signatures and corresponding experimental constraints.
We show that the well known Georgi-Machacek (GM) model can be realized as a limit of the recently constructed Supersymmetric Custodial Higgs Triplet Model (SCTM) which in general con- tains a significantly more complex scalar spectrum. We dub this limit of the SCTM, which gives a weakly coupled origin for the GM model at the electroweak scale, the Supersymmetric GM (SGM) model. We derive a mapping between the SGM and GM models using it to show how a supersym- metric origin implies constraints on the Higgs potential in conventional GM model constructions which would generically not be present. We then perform a simplified phenomenological study of diphoton and ZZ signals for a pair of benchmark scenarios to illustrate under what circumstances the GM model can mimic the SGM model and when they should be easily distinguishable.
The fermion mass hierarchy does not have an explanation in the Standard Model (SM). Moreover, an inverted hierarchy of the sfermion masses is suggested by the constraints from LHC data. To explain these known and expected hierarchies, we consider a supersymmetric model that uses partial-compositeness. The Higgs and third-generation matter superfields are elementary while the first two matter generations are composite with supersymmetry assumed to be broken by the strong dynamics. Linear mixing between elementary superfields and supersymmetric composite operators with large anomalous dimensions is responsible for simultaneously generating the fermion and sfermion mass hierarchies. This partial-compositeness framework can be considered to be dual by the AdS/CFT correspondence to the idea of a warped extra dimension that explains the mass hierarchies by wavefunction overlap.
We study the low scale predictions of supersymmetric standard model extended by $U(1)_{B-L}\times U(1)_{R}$ symmetry, obtained from $SO(10)$ breaking via a left-right supersymmetric model, imposing universal boundary conditions. Two singlet Higgs fields are responsible for the radiative $U(1)_{B-L}\times U(1)_{R}$ symmetry breaking, and a singlet fermion $S$ is introduced to generate neutrino masses through inverse seesaw mechanism. The lightest neutralino or sneutrino emerge as dark matter candidates, with different low scale implications. We find that the composition of the neutralino LSP changes considerably depending on the neutralino LSP mass, from roughly half $U(1)_R$ bino, half MSSM bino, to singlet higgsino, or completely dominated by MSSM higgsino. The sneutrino LSP is statistically much less likely, and when it occurs it is a 50-50 mixture of right-handed sneutrino and the scalar $\widetilde{S}$. Most of the solutions consistent with the relic density constraint survive the XENON 1T exclusion curve for both LSP cases. We compare the two scenarios and investigate parameter space points and find consistency with the muon anomalous magnetic moment only at the edge of $2\sigma$ deviation from the measured value. However, we find that the sneutrino LSP solutions could be ruled out completely by strict reinforcement of the recent $Z^\prime $ mass bounds. We finally discuss collider prospects for testing the model.
We use the IR fixed point predictions for gauge couplings and the top Yukawa coupling in the MSSM extended with vectorlike families to infer the scale of vectorlike matter and superpartners. We present results in detail for the MSSM extended with one complete vectorlike family. We find that for a unified gauge coupling αG>0.3 vectorlike matter or superpartners are expected within 1.7 TeV (2.5 TeV) based on all three gauge couplings being simultaneously within 1.5\% (5\%) from observed values. This range extends to about 4 TeV for αG>0.2. We also find that in the scenario with two additional large Yukawa couplings of vectorlike quarks the IR fixed point value of the top Yukawa coupling independently points to a multi-TeV range for vectorlike matter and superpartners. Assuming a universal value for all large Yukawa couplings at the GUT scale, the measured top quark mass can be obtained from the IR fixed point for tanβ≃4. The range expands to any tanβ>3 for significant departures from the universality assumption of the Yukawa couplings.
We use Pauli-Villars regularization to evaluate the conformal and chiral anomalies in the effective field theories from $Z_3$ and $Z_7$ compactifications of the heterotic string without Wilson lines. We show that parameters for Pauli-Villars chiral multiplets can be chosen in such a way that the anomaly is universal in the sense that its coefficient depends only on a single holomorphic function of the three diagonal moduli. It is therefore possible to cancel the anomaly by a generalization of the four-dimensional Green-Schwarz mechanism. In particular we are able to reproduce the results of a string calculation of the four-dimensional chiral anomaly for these two models.
The LHC is quickly closing the naturalness window of the MSSM, current limits in parameter space are about to outpace the discovery potential of minimal SUSY models. (For example, current gluino mass bounds are close t to overtaking the highest discoverable mass with 3 inverse atto-barns of data.) As such, I will enumerate and explore the models and phenomenology of still unconstrained SUSY scenarios at LHC in unconventional and extended SUSY scenarios. This will include including the identification of new production modes and interesting decay chains for a variety of standard and non-standard SUSY particles, considering various LSP and NLSP candidates. I will also present possible searches for the High Luminosity run of LHC that could increase the discovery potential of super-partners in more standard channels.