Choose timezone
Your profile timezone:
Powered by Indico
v3.3.2-pre
The 2016 Phenomenology Symposium will be held May 9-11, 2016 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 ended April 17, 2016
Registration closed May 1, 2016.
Talk submission ended April 24, 2016
Conference banquet May 10, 2016
Plenary program and full program are now available.
Plenary topics and speakers:
Parallel session mini-reviews:
PITT PACC Travel Awards: With support from the NSF and DOE, there are a number of awards (up to $300 each) available to domestic graduate students for travel and accommodation to Pheno 16. A student applicant should send an updated CV and a statement of financial need, and arrange for a short recommendation letter sent from their thesis advisor, by email to pittpacc+award@pitt.edu. The decision will be based on the academic qualification, the talk submission to Pheno 16, and the financial need. The deadline for the application is April 10, and the winners will be notified by April 18. (Each research group may be limited to one awardee. Winners in the previous years may have lower priority for consideration. Winner institutes and names will be announced at the Symposium banquet.)
PHENO 2016 ORGANIZERS: Brian Batell, Cindy Cercone, Ayres Freitas, Tao Han (chair), Adam Leibovich, Satyanarayan Mukhopadhyay, and Brock Tweedie
PHENO 2016 PROGRAM ADVISORS: Vernon Barger, Lisa Everett, Kaoru Hagiwara, JoAnne Hewett, Arthur Kosowsky, Tilman Plehn, Xerxes Tata, Andrew Zentner, and Dieter Zeppenfeld.
OTHER ANNOUNCEMENTS
SM@LHC 2016 will be held at the University of Pittsburgh during May 3-6, 2016
We present several interesting phenomenological implications in a model of neutrino masses which is constructed within the framework of the electroweak-scale right-handed neutrino (EW-$\nu_R$) model by applying a horizontal $A_4$ symmetry. The one-loop induced lepton flavor violating radiative decays $\mu \to e \gamma$ and $\mu$-e conversion might be related to each other under a good approximation that we have established. Implications concerning future searches for $\mu$-e conversion at Fermilab and J-PARC COMET are also discussed.
In this paper we examine the constraints dedicated LHC multi lepton searches can place on $Z'$ bosons coming from gauged muon number minus tau number, $L_{\mu}-L_{\tau}$. As the $L_{\mu}-L_{\tau}$ gauge boson does not couple to proton constituents or electrons at tree level, the current bounds are fairly loose, especially for $M_{Z'} < 1~ \rm GeV$. For $2m_{\mu} < M_{Z'} < M_Z/2$ we develop search strategies using the $pp \to Z \to 4\, \mu$ channel. The cleanliness of the final state, combined with the fact that $pp \to Z \to 4 e$, $Z \to 2e\,2\mu$ can be used as background control samples, allow us to spot $L_{\mu}-L_{\tau}$ $Z'$ with couplings $\mathcal O(10^{-4})$ times the Standard Model couplings with Matrix Element method. For lighter $Z'$, we propose the mode $pp \to 2\mu + \displaystyle{\not} E_T$. The presence of missing energy means there is a wider set of backgrounds to consider in this final state, such as Drell-Yan production of leptonically decaying $\tau$ pairs, however we find these can be controlled with careful cuts.
Leptons couple to the Higgs doublet of the standard model to acquire mass. This coupling is at tree level in the standard model, but in this talk we look at a specific model where the tree level coupling is forbidden by imposing $A_4$ symmetry. Therefore leptons couple to Higgs through a loop. As we will see in this talk, with radiative mass we can have loop contributions without the $16\pi^2$ loop suppression factor.
We analyze the important consequences of this scenario, including
Higgs decay, muon anomalous magnetic moment, µ → eγ, µ → eee, and the proposed
dark sector.
The LHC has reported a slight excess in the $h \to \tau \mu$ channel. If this lepton flavor violating decay is confirmed, an extension of the Standard Model (SM) will be required to explain it. A possibility to accommodate it is a model where the Higgs couples to new vectorlike fermions that in turn couple to the SM leptons through a flavor-violating four fermion interaction. The excess can be successfully explained while satisfying all other flavor constraints, with order one couplings, vectorlike fermion masses as low as 15 TeV, and a UV scale higher than 35 TeV.
The Standard Model contains four accidental, or potentially emergent, global $U(1)$ symmetries. It is possible that these symmetries are indicative of a hidden gauge structure that would couple to some anomaly-free combination of the associated currents. This would result in a new Abelian gauge boson known as a $Z'$, which would be massive if the gauge-symmetry were spontaneously broken.
Shuve and Yavin managed to show that the existence of a massive $Z'$ coupled to a sterile neutrino via mass-mixing provides a viable Dodelson-Widrow-esque dark matter production mechanism. In this talk we will investigate the implications of adding an order parameter charged under the new symmetry, a set of sterile neutrinos, and the new $Z'$ to the Standard Model. The sterile neutrinos will induce an active neutrino mass matrix, whose compatibility with the Shuve-Yavin mechanism will be investigated. We find a generic relationship that suggests sterile neutrino dark matter should not contribute significantly to active neutrino phenomenology.
Observation of non-zero neutrino masses at a scale $\sim 10^{-1} - 10^{-2}$ eV is a major problem in otherwise highly successful Standard Model. The most elegant mechanism to explain such tiny neutrino masses is seesaw mechanism with right handed neutrinos. However, the required seesaw scale is so high ($\sim 10^{14}$ GeV), it will not have any direct collider implications. Recently, in our explicit model the seesaw mechanism with the right handed ‘fertile’ neutrinos at the electroweak scale has been investigated. The model has a mirror symmetry having left and right lepton and quark doublets and singlets for the same $SU(2)_W $ gauge symmetry. Additional Higgs multiplets are introduced to satisfy the precision electroweak tests, and other low energy observables. Because the scale of the symmetry breaking is electroweak, both the mirror quarks and mirror leptons have masses in the electroweak scale in the range $ \sim 150 - 800 $ GeV. The mirror quarks \ leptons decay to SM quarks \leptons and almost massless neutral scalars. We calculate the final state signals arising from the pair productions of these mirror quarks and leptons and their subsequent decays. We find distinguished like-sign di-lepton signals from mirror lepton decays which are well observable over SM background for $13$ TeV LHC. Moreover, depending on the associated Yukawa couplings, these decays can also give rise to displaced vertices with long decay length (very different from the usual displaced vertices associated with b decays), which will be the distinguishing signatures to look for in $13$ TeV LHC.
In this talk, we show that the model of right-handed neutrinos at the electroweak scale satisfies two important tests: the electroweak precision measurements and the 125 GeV Higgs discovery. In the model, the right-handed neutrinos along with the newly proposed mirror-charged leptons are components of $SU(2)$ doublets: $\nu_R$s here are non-sterile or fertile. The new particle content of the model is proved to satisfy well the electroweak precision constraints. We also show the dual nature of the 125 GeV Higgs boson candidate in our model.
Realistic neutrino mass models often predict the existence of electroweak- and TeV-scale heavy neutrinos that couple to Standard Model particle via mixing with left-handed neutrinos. However, owing to the large differences between the neutrino mass scales investigated and QED/QCD radiation scales typical of hadron colliders, recent calculations have been plagued with soft and collinear divergences, leading to erroneous predictions for the LHC and beyond.
A self-consistent treatment of heavy neutrino production mechanisms free of such divergences is presented. This includes: gluon fusion (GF) matched with 1 extra jet, charged and neutral current Drell-Yan (DY), DY + n-jets, and vector boson (VBF) fusion. Associated FeynRules/NLOCT and MG5_amc@NLO model files are publicly available.
At 14 TeV, we find that the LO GF rate is small and comparable to the NLO Charged Current DY+1j rate; at a future 100 TeV collider, GF dominates for neutrino masses up to 1.5 TeV, after which VBF takes lead.
Based on Degrande, et al: http://arxiv.org/abs/1602.06957
Inflection-point inflation is a unique possibility to realize a successful slow-roll inflation
when inflation is driven by a single scalar field with an initial value below the Planck mass.
In order for a re-normalization group (RG) improved effective $\lambda(\phi) \phi^4$ potential
to develop an inflection point, the self-coupling $\lambda(\phi)$ must exhibit a minimum
with an almost vanishing value, $\lambda_{\min} \simeq 0$, in its RG evolution.
We investigate a possibility of realizing the inflection-point inflation driven by the B-L Higgs field
in the minimal gauged B-L extended Standard Model (SM) at the TeV scale. For a realistic
inflection-point inflation, the mass ratios among the Z' gauge boson, the right-handed neutrinos
and the B-L Higgs boson are fixed, which can be tested in the future collider experiments.
I will overview the main characteristics of primordial helical fields. I will discuss the (nearby) scale invariant helical magnetic fields generated during inflation. It will be shown that if magnetic helicity of such fields is measured, it can be used to determine the beginning of inflation. Upper bounds on magnetic helicity can be used to derive constraints on the minimal duration of inflation. Observational constraints on magnetic helicity will be addressed
It is usually assumed that the inflationary fluctuations start from the Bunch-Davies (BD) vacuum and the iε prescription is used when interactions are calculated. We show that those assumptions can be verified explicitly by calculating the loop corrections to the inflationary two-point and three-point correlation functions. Those loop corrections can be resumed to exponential factors, which suppress non-BD coefficients and behave as the iε factor for the case of the BD initial condition. A new technique of loop chain diagram resummation is developed for this purpose. For the non-BD initial conditions which is setup at finite time and has not fully decayed, explicit correction to the two-point and three- point correlation functions are calculated. Especially, non-Gaussianity in the folded limit is regularized due to the interactions.
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation $H_{I}$. If the scale of Peccei-Quinn (PQ) breaking $f_a$ is greater than $\frac{H_{I}}{2\pi}$, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation require late-time dilution of the axion abundance. Even then, $f_a$ must be below the grand unification scale. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow $f_a$ close to the Planck scale. Avoiding disruption of inflationary dynamics provides important limits on the parameter space.
Axion stars are condensed states of large numbers of axion particles, bound by self-gravitation and attractive self-interactions. Such states generically arise in theories of light scalars, where the critical temperature for the transition is very high. By solving the semiclassical equations of motion, we find the maximum gravitationally stable mass for weakly bound axion stars. Further, the Hermiticity of the axion field leads to number-changing processes in the axion potential, and consequently a finite lifetime for axion stars which bounds their masses from below. These bounds taken together, along with astrophysical constraints on the mass of QCD axions, constrain significantly the allowed parameter space for axion stars. The consequences for axionic dark matter will also be discussed.
If the dark matter particles are axions,
gravity can cause them to coalesce into axion stars,
which are stable gravitationally bound systems of axions.
In the previously known solutions for axion stars,
gravity and the attractive force between pairs of axions are
balanced by the kinetic pressure.
The mass of these dilute axion stars cannot exceed a critical mass,
which is about $10^{-14} M_\odot$ if the axion mass is $10^{-4}$~eV.
We study axion stars using a simple
approximation to the effective potential of the
nonrelativistic effective field theory for axions.
We find a new branch of dense axion stars
in which gravity is balanced by the mean-field pressure of the axion Bose-Einstein condensate.
The mass on this branch ranges from
about $10^{-20} M_\odot$ to about $M_\odot$.
If a dilute axion star with the critical mass accretes additional axions and collapses,
it could produce a bosenova, leaving a dense axion star as the remnant.
The discovery of the Higgs boson marks a key ingredient to establish the electroweak structure of the Standard Model. Its non-abelian gauge structure gives rise to, yet unobserved, non-perturbative baryon and lepton number violating processes. We propose to use cosmic ray air showers, as mea- sured, for example, at the Pierre Auger Observatory, to set a limit on the hadronic production cross section of sphalerons. We identify several observables to discriminate between sphaleron and QCD induced air showers.
The search for the origin(s) of ultra-high energy (UHE) cosmic rays (CR) remains one of the cornerstones of high energy astrophysics. The previously proposed sources of acceleration for these UHECRs were gamma-ray bursts (GRB) and active galactic nuclei (AGN) due to their energetic activity and powerful jets. However, a problem arises between the acceleration method and the observed CR spectrum. The CRs from GRBs or AGN jets are assumed to undergo Fermi acceleration and a source injection spectrum proportional to E^-2 is expected. However, the most recent fits to the spectrum and nuclear composition suggest an injection spectrum proportional to E^-1. It is well known that such a hard spectrum is characteristic of unipolar induction of rotating compact objects. When this method is applied to the AGN cores, they prove to be much too luminous to accelerate CR nuclei without photodisintegrating, thus creating significant energy losses. Instead, here we re-examine the possibility of these particles being accelerated around the much less luminous quasar remnants, or dead quasars. We compare the interaction times of curvature radiation and photodisintegration, the two primary energy loss considerations with the acceleration time scale. We show that the energy losses at the source are not significant enough as to prevent these CRs from reaching the maximum observed energies. Using data from observatories in the northern and southern sky, the Telescope Array and the Pierre Auger Observatory respectively, two hotspots have been discerned which have some associated quasar remnants that help to motivate our study.
The search for dark matter, which makes up to 25% of the mass of the universe, is one of today's most exciting fields of particle physics. As bigger detectors are being built to increase their sensitivity, background reduction is an ever more challenging issue. To this end, a new type of dark matter detector is being developed, a liquid xenon bubble chamber, which would combine the strength of liquid xenon TPCs, namely event by event energy resolution, with that of a bubble chamber, namely insensitivity to electronic recoils. In addition, it would be the first time ever that a dark matter detector is active on all three detection channels, ionization and scintillation characteristic of xenon detectors, and heat through bubble formation in superheated fluids. Preliminary simulations have shown that, depending on the threshold, a discrimination of 99.99% to 99.9999+% can be achieved, which is on par or better than many current experiments. Finally, such a detector, being both gaseous and liquid, could potentially punch through the neutrino floor using directionality.
I will talk about the idea of dark matter velocity spectroscopy and its application for sterile neutrino dark matter searches: how high-resolution x-ray instruments can distinguish line emission from dark matter, hot gas, and instrumental artifacts. With a sufficiently precise instrument, this general technique can provide an additional and important handle in diagnosing tentative dark matter line signals.
Hunting for neutrinos arising from captured dark matter annihilating in the Sun has long been one of the main indirect-detection search strategies. This strategy, however, has been thought to be largely insensitive to dark matter which annihilates purely to light quarks. In this talk I will discuss prospects for probing these types of models by focusing on \textit{monoenergetic} neutrinos, which arise from decays of hadronic annihilation byproducts which are stopped within the core of the Sun. I will show that we can obtain competitive and complementary sensitivities for few-GeV dark matter using this strategy.
Dark matter (DM) annihilations have been widely studied as a possible explanation of excess gamma rays from the galactic center seen by Fermi/LAT. However, most such models are in conflict with constraints from dwarf spheroidals. Motivated by this tension, I will show in this talk that p-wave annihilating dark matter can easily accommodate both sets of observations due to the lower DM velocity dispersion in dwarf galaxies. Explaining the DM relic abundance is then challenging. I will outline a scenario in which the usual thermal abundance is obtained through s-wave annihilations of a metastable particle that eventually decays into the p-wave annihilating DM of the present epoch. The couplings and lifetime of the decaying particle are constrained by big bang nucleosynthesis, the cosmic microwave background, and direct detection, but significant regions of parameter space are viable. A sufficiently large p-wave cross section can be found by annihilation into light mediators that also give rise to Sommerfeld enhancement. A prediction of the scenario is enhanced annihilations in galaxy clusters.
In this talk I will discuss the indirect detection signals for a self-consistent hidden U(1) sector, containing a fermionic dark matter candidate, dark Z' gauge boson and a dark Higgs. The presence of the scalar, the dark Higgs, provides a mass generation mechanism for the dark sector particles, and for some couplings is required in order to avoid unitarity violation at high energies. I will show that the inclusion of this scalar to the sector opens up a new s-wave annihilation channel for indirect detection searches, providing rich phenomenology.
Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. Contrary to similar studies that implement pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments like LUX-ZEPLIN will cover large regions of parameter space for TeV-scale thermal dark matter. Decays of the heavy charged $W^\prime$ boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when fixing to the observed Run 1 excesses, thus favoring the theoretically attractive scenario $g_R = g_L$. This region of parameter space may be probed by future collider searches for new Higgs bosons or electroweakinos.
We present a model of dark matter where the mediator that connects the dark sector to the Standard Model is tied to electroweak symmetry breaking through the composite Higgs scenario. A non-minimal coset space furnishes pseudo-Nambu–Goldstone bosons that include both the Higgs and the additional gauge-singlet mediator. This contrasts with typical extensions of Higgs portal models in that it does not invoke a two Higgs doublet model while also prescribing a set of couplings between the Higgs and the mediator. While this construction is general, we focus on the simplest non-minimal composite Higgs coset, SO(6)/SO(5). This scenario presents a distinct phenomenology from typical UV-complete models of pseudoscalar mediators and is a novel way to connect composite Higgs models to dark matter.
An overview of the latest studies of the recently discovered Higgs boson decaying into pairs of bosons is presented: to pairs of W's Z's and photons. These results include the latest data from CMS experiment, collected from 13 TeV LHC Run 2 in 2015.
First 13 TeV results on the searches for the production of the Higgs boson in association with a top quark pair in the CMS experiment are presented.
A search is presented for the non-resonant production of two Higgs bosons decaying into two bottom quarks, and two photons or two tau leptons. The data collected with the CMS detector are used, corresponding to a maximum integrated luminosity of 19.7 inverse femtobarns for the proton-proton collisions at sqrt(s) = 8 TeV and 2.7 inverse femtobarns for the proton-proton collisions at sqrt(s) = 13 TeV. Good agreement is observed between data and predictions of the standard model (SM). Although the sensibility to the SM non-resonant production is really small, the limits constrain the parameter space for anomalous Higgs boson couplings, and allow the exclusion of some very extreme models.
In this talk I will present the computation of the analytical NLO virtual corrections to the $gg\rightarrow HH$ cross section. The reducible contributions, given by the double-triangle diagrams, are evaluated exactly while the two-loop irreducible diagrams are evaluated by an asymptotic expansion in heavy top quark mass. I will briefly describe the techniques involved and their range of validity, and compare our computation with the known numerical results.
In this talk I will discuss the implementation of the next-to-leading order QCD corrections to electroweak Higgs boson plus three jet production at the CERN Large Hadron Collider experiment within the Matchbox framework of the Herwig 7 event generator. Numerical results for integrated cross sections and kinematics distributions will be presented.
I will talk about the effect of multiple parton radiation to Higgs boson plus jet production at the LHC, by applying the transverse momentum dependent (TMD) factorization formalism to resum large logarithmic contributions to all orders in the expansion of the strong interaction coupling. I will show that the transverse momentum distribution of the Higgs boson, particularly near the lower cut-off applied on the jet transverse momentum, can only be reliably predicted by the resummation calculation which is free of the so-called Sudakov-shoulder singularity problem, present in fixed-order calculations.
In this talk the computation of soft gluon resummation for $pp \to t\bar{t}H$ will be presented. The absolute threshold resummation is carried out at NLL accuracy. This is the first application for the Mellin space technique to $2 \to 3$ type processes. The impact of resummation on the numerical prediction for the total cross section and the theoretical uncertainties will be presented.
The 125GeV Higgs boson was discovered by the ATLAS and CMS Collaboration in 2012. With an increasing dataset, the emphasis has now shifted to determining the properties of this particle and testing the consistency of the Standard Model against the data.In this talk, the recent results from Run1 on the 125GeV Higgs boson are summarized. With the re-start of the LHC in 2015, the detailed Higgs boson property measurements will be extended to reach subsequently a higher precision compared to the 7 and 8 TeV analyses. Latest study of the Higgs boson results in Run2 via yy and ZZ*(4l) channels are presented, and search for the Higgs boson under the assumption of different theory models, such as: Randall–Sundrum (RS) model and two-Higgs-doublet model (2HDM) are also outlined.
SUSY confronts the LHC
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 searches for supersymmetric squarks and gluinos, including third generation squarks produced in the decay of gluinos. The searches have been performed on the pp collisions collected at 13 TeV center of mass energy and involve final states containing jets, missing transverse momentum with and without leptons.
Theories beyond the standard model such as Supersymmetry (SUSY) predict the existence of additional particles. Cascade decays of SUSY particles often yield final states with hadronic activity and missing transverse energy.
Signatures including leptons are of particular interest since standard model processes are suppressed by this selection and can be predicted with good accuracy.
An overview of SUSY searches in single lepton or opposite-sign dilepton final states with the CMS detector at the CERN LHC is presented with focus on the first results from proton-proton collisions at $\sqrt{s}=13$ TeV.
The latest results from supersymmetry searches performed at CMS at 13 TeV in final states characterized by the presence of either a pair of same-sign charged leptons (muons or electrons), or by the presence of at least 3 charged leptons are presented. The studies focus particularly in the search for gluino pair production, and the results are interpreted in the context of simplified models of supersymmetry.
Contrary to common expectations, a left-sneutrino can turn out to be the
lightest supersymmetric (SUSY) particle (LSP), if there is a mass-splitting
between the CP-even and-odd components of the complex sneutrino field(s).
A signal expected of the ensuing SUSY spectrum, over a large region of the
parameter space, is same-sign trileptons at the LHC. The jets + MET signal
can be suppressed in this case, thus enhancing the scope of leptonic
signals.
The new energy regime reached at the LHC with the Run1 is a unique chance to look for the production of new massive particles, predicted by many beyond-Standard-Model theories. Among these, Supersymmetry (SUSY) is particularly favourable because it provides a solution to the hierarchy problem, it ensures gauge coupling unification and provides a candidate for dark matter. The Run 2 of LHC has been successful, and the experiments have delivered excellent results on the new data. This talk presents the CMS results on the search for SUSY in all-hadronic final states, using several different approaches, with an integrated luminosity of approximately 2.3 inverse femtobarn. No significant excess is observed and exclusion is derived in the parameter space of simplified SUSY models.
In this talk, the latest results on searches for supersymmetry in final states with photons are presented using data recorded by the CMS experiment. A variety of complementary final state signatures and methods are used to probe gluino, squark and electroweak production of supersymmetric particles.
Top quark mass measurements from the CMS experiment at the LHC. The talk will present an overview of the current status of the results from the lepton+jets, dilepton and all-jets channels.
The top quark is unique among the known quarks in that it
decays before it has an opportunity to form hadronic bound
states. This makes measurements of its properties particularly
interesting as one can access directly the properties of a bare
quark. The latest measurements of these properties are
presented. Measurements of the charge asymmetry in top-quark pair,
which probe models of physics beyond the Standard Model, are
presented; these include measurements at high invariant masses of the
ttbar system using boosted top quarks. Measurements of the top
polarisation produced either through pair process or through single
top process are discussed. The helicity of the W boson from the top
decays and the production angles of the top quark are further
discussed. Limits on the rate of flavour changing neutral currents in
the production or decay of the top quark are discussed.
The latest ATLAS measurements of the top quark mass are also
presented. A measurement using lepton+jets events is presented, where
a multi-dimensional template fit is used to constrain the
uncertainties on the energy measurements of jets. The measurements
using dilepton and all-hadronic events are also discussed. In
addition, measurements aiming to measure the mass in a well-defined
scheme are presented like the measurement using ttbar production with
an additional jet to extract the top quark mass in the pole-mass
scheme.
The complex pole mass of the top quark is presented at full two-loop order in the Standard Model, augmenting the known four-loop QCD contributions. The input parameters are the MS-bar Yukawa and gauge couplings, the Higgs self-coupling, and the Higgs vacuum expectation value (VEV). Here, the VEV is defined as the minimum of the full effective potential in Landau gauge, so that tadpoles vanish. This is an alternative to earlier results that instead minimize the tree-level potential, resulting in a VEV that is gauge-fixing independent but accompanied by negative powers of the Higgs self-coupling in perturbative expansions. The effects of non-zero Goldstone boson mass are eliminated by resummation. I also study the renormalization scale dependence of the calculated pole mass.
see summary/abstract.
This talk is on behalf of the ATLAS Collaboration.
We will review the latest results from CMS at 13 TeV measuring the production cross section of top pairs and single top.
Abstract.
Measurements of single top-quark production in proton-proton collisions are presented at a centre-of-mass energy of $8\,$TeV and $13\,$TeV. A measurement of the cross-section where a W boson is exchanged in the $t$-channel is discussed and the results for the inclusive production cross-section are presented. A measurement of the production cross-section of a single top quark in association with a W boson, the second largest single-top production mode, is also presented. Evidence for single-top production in the $s$-channel with the $8\,$TeV ATLAS dataset is discussed. Finally, measurements of the properties of the Wtb vertex allows to set limits on anomalous couplings. All measurements are compared to state-of-the-art theoretical calculations.
The abundance of top-quarks at the LHC allows us to test subtle features such as the charge asymmetry in heavy-quark pair production. A promising observable of this fundamental property of QCD is the top-antitop energy asymmetry in jet-associated top-pair production. I will present new predictions of the energy asymmetry beyond the leading order and venture an outlook on the discovery prospects during run II.
I will present some recent progresses and ongoing efforts in developing the SM EFT to next-to-leading order (NLO) accuracy, with a focus on operators involving the top-quark and the Higgs boson fields. Apart from total rate, NLO results matched to the parton shower simulation are also available, allowing for event generation to be directly employed in experimental analyses. Loop-induced processes can be incorporated in the same framework. I will also discuss some results on single-top and ttZ/photon processes.
The 2 Higgs Doublet Model provides a natural extension of the Higgs sector, and predicts new high mass Higgs bosons, scalar or pseudo-scalar. This presentation reports on the searches of these particles by the ATLAS collaboration, using the first run-2 data of 3.2 fb$^{-1}$ at 13 TeV.
The observation of a Higgs-like boson with a mass near 125 GeV/c2 at the Large Hadron Collider raises a critical question of whether the new particle is in fact the SM Higgs boson. Searches for non-SM Higgs boson production and its decay modes are therefore complementary.
I will report the searches for extended Higgs sectors performed with the CMS detector. I will focus on the NMSSM model, which is an extension of the minimal supersymmetric standard model (MSSM) by an additional gauge singlet field under new U(1)PQ symmetry in the Higgs sector of the superpotential.
Compared to the MSSM, the NMSSM naturally generates the mass parameter mu in the Higgs superpotential at the electroweak scale and significantly reduces the amount of fine tuning required. The Higgs sector of the NMSSM consists of 3 CP-even Higgs bosons h1,2,3 and 2 CP-odd Higgs bosons a1,2.
The latest CMS results, and prospects for Run 2 will be discussed.
The discovery of a 125 GeV Higgs boson at the Large Hadron Collider strongly motivates direct searches for additional Higgs bosons. In a type I two Higgs doublet model there is a large region of parameter space at tanβ>5 that is currently unconstrained experimentally. We show that the process gg→H→AZ→ZZh can probe this region, and can be the discovery mode for an extended Higgs sector at the LHC. We analyze 9 promising decay modes for the ZZh state, and we find that the most sensitive final states are ℓℓℓℓbb, ℓℓjjbb, ℓℓννγγ and ℓℓℓℓ+missing energy.
In models with extended Higgs sector and vectorlike leptons, the decay of a heavy Higgs boson can be dominated by cascade decays through new leptons. In this talk I will discuss these novel decay topologies focussing on a Higgs cascade decay where the SM Higgs is involved in the process. In this case we expect three resonance signals from combining the final states, which are quite promising in the search of new physics signals at the LHC.
An effective theory of the Higgs sector allows us to analyze kinematic distributions in addition to inclusive rates. But the precision of Higgs measurements at the LHC cannot guarantee a clear hierarchy of scales, casting doubt on the validity of the effective model. We analyze how well dimension-6 operators describe LHC observables in comparison to the full theory. As benchmarks we consider a singlet extension of the Higgs sector, a two-Higgs-doublet model, new top partners, and a vector triplet, focussing on parameter ranges where the LHC will be sensitive. We discuss which Higgs observables are correctly described by the dimension-6 approximation, where it breaks down, and whether this presents a problem for LHC analyses.
The effective Lagrangian expansion provides a model independent framework to study effects of new physics at the electroweak scale. To make full use of LHC data in constraining higher-dimensional operators we need to include both the Higgs and the electroweak gauge sector in the analysis. We first present a combined analysis of the relevant diboson production LHC results to set the strongest available constraints on triple gauge boson couplings. The bounds that we derive are already stronger than the ones obtained from LEP data. Next, we show how they can be combined with Higgs measurements at the LHC to control effectively correlations in the multi-dimensional space of dimension–six Wilson coefficients, further constraining the current allowed space.
diphoton, dijet and dilepton searches
Searches for physics beyond the Standard Model are performed in high-pT lepton final states, with or without jets, using the ATLAS experiment. These searches target a large range of beyond the Standard Model phenomenology ranging from new massive W’ or Z’ bosons, lepton flavour violation, extra dimensions, contact interactions, leptoquarks, excited leptons and strong gravity effects. The full 2015 LHC proton-proton dataset is combined with the data which has been collected so far during 2016, at $\sqrt{s}$ = 13 TeV.
Collider limits on new narrow resonances often reference specific new models, making it difficult to draw general conclusions. In this talk we discuss simplified limits which allow collider results to be displayed in a way which allows constraints on different models to be easily derived from experimental data. We show examples from recent searches for diboson and diphoton resonances at the LHC.
Beyond the standard model theories like Extra-Dimensions and Composite Higgs scenarios predict the existence of very heavy resonances compatible with a spin 0 (Radion),spin 1 (W’, Z’) and spin 2 (Graviton) particle with large branching fractions in pairs of standard model bosons and negligible branching fractions to light fermions. We present an overview of searches for new physics containing W, Z or H bosons in the final state, using proton-proton collision data collected with the CMS detector at the CERN LHC. Many results use novel analysis techniques to identify and reconstruct highly boosted final states that are created in these topologies. These techniques provide increased sensitivity to new high-mass particles over traditional search methods.
Many extensions to the Standard Model predict new particles decaying into two bosons. Searches for diboson resonances (WW, WZ, ZZ, WH, ZH, and HH) have been performed in final states with different numbers of leptons and using new identification techniques to disentangle the decay products in highly boosted hadronic topologies. This talk summarizes the set of such searches carried out by the ATLAS collaboration with LHC Run 2 data.
Searches for scalar resonances are presented, using the first run-2 data of 3.2 fb^(-1) at 13 TeV. The searches use the gamma-gamma, Z-gamma, ZZ and WW decay channels, and cover a large range of masses for the hypothetical resonances.
The CMS collaboration has reported a 2.8$\sigma$ excess in the search of the $SU(2)_R$ gauge bosons decaying through right-handed neutrinos into the two electron plus two jets (eejj) final states. This can be explained if the $SU(2)_R$ charged gauge bosons $W_{R}^\pm$ have a mass of around 2 TeV and a right-handed neutrino with a mass of $\cal{O}(1)$ TeV mainly decays to electron. Indeed, recent results in several other experiments, especially that from the ATLAS diboson resonance search, also indicate signatures of such a 2 TeV gauge boson. However, a lack of the same-sign electron events in the CMS eejj search challenges the interpretation of the right-handed neutrino as a Majorana fermion. Taking this situation into account, in this paper, we consider a possibility of explaining the CMS eejj excess based on the $SU(2)_L$ ⊗ $SU(2)_R$ ⊗ $U(1)_{B−L}$ gauge theory with pseudo-Dirac neutrinos. We find that both the CMS excess events and the ATLAS diboson anomaly can actually be explained in this framework without conflicting with the current experimental bounds. This setup in general allows sizable left-right mixing in both the charged gauge boson and neutrino sectors, which enables us to probe this model through the trilepton plus missing-energy search at the LHC. It turns out that the number of events in this channel predicted in our model is in good agreement with that observed by the CMS collaboration. We also discuss prospects for testing this model at the LHC Run-II experiments.
I explore the phenomenology of various models in which scalar fields that decay to pairs of Standard Model Bosons. I consider extending the SM with scalars/pseudo-scalars in singlet and adjoint representation of SM gauge groups. I first find the most general set of dimension 5-7 effective operators which produce the scalar-boson coupling, then specify UV completions, including supersymmetric models. Using these effective operators, I explore present an exploration map for di-boson models by systematically considering scalar event signatures including; gluon-photon , gluon Z ,WZ, tri-boson, di-jet and of course di-photon. I recast several analyses from Run I of the LHC to find constraints on models, and project the discovery potential in various channels for the 14 TeV run of LHC.
This talk will discuss the physics program and detector set-up of the proposed SHiP experiment at the SPS at CERN, Geneva,
Switzerland. The SHiP experiment is a proposal for a new general-purpose fixed target facility to search for hidden particles as predicted by a very large number of recently elaborated models of Hidden Sectors which are capable of accommodating dark matter, neutrino oscillations, and the origin of the full baryon asymmetry in the Universe. Specifically, the experiment is aimed at searching for very weakly interacting long lived particles including Heavy Neutral Leptons - right-handed partners of the active neutrinos; light supersymmetric particles - sgoldstinos, etc; scalar, axion and vector portals to the hidden sector.The high intensity of the SPS and in particular the large production of charm mesons with the 400 GeV beam allow accessing a wide variety of light long-lived exotic particles of such models and of SUSY. Moreover, the facility is also suited to study the interactions of tau neutrinos. SHiP is currently a collaboration of 46 institutes from 15 countries.
Dark photons appear in many well-motivated dark matter scenarios, which leads to a worldwide effort to search for them. In this talk, I will present two novel search methods for dark photons at the LHCb experiment. One is an exclusive search in charm meson decay, and the other is a fully data-driven inclusive search based on di-muon resonances. These searches advance particle physics by showing how LHCb can have sensitivity to large regions of unexplored dark-photon parameter space.
Kinetic mixing is a common and well motivated phenomenon in BSM theories that can naturally provide a weak interaction between the standard model and new physics. Nonabelian kinetic mixing necessarily introduces a new mass scale which is related to the kinetic mixing strength. In this talk I will show that this mass scale - mixing strength relationship maps the parameter space relevant to current and near future fixed-target experiments to mass scales being probed at the LHC. I will then go on to present a model of nonabelian kinetic mixing and discuss its phenomenological implications.
LEP measurements of the Z width highly constrain new electroweak states with masses less than half the Z mass. Therefore, in this work we consider effective operators involving a fermionic dark matter which contribute to the Z invisible width only at loop level. How FCC-ee projections compare to direct detection bounds within these models will be the primary focus of the discussion. Possible UV completions for these operators will also be examined.
A light sub-GeV Higgs that can accommodate muon g-2 anomaly can be probed in various low energy experiments, such as muon decay, charged kaon decays, etc. I will first discuss it in a model-independent way and then provide a concrete UV model where the light scalar can be realized. The proposed muon electric dipole moment will also have a sensitivity to some part of parameter space. Lepton flavor violating decays due to the light scalar will also be discussed.
There has recently been a proposal to build a new detector at the Large Hadron Collider to search for so called 'milli-charged' particles. This experiment would search for particles beyond the standard model with masses up to 100GeV, and fractional electric charges as low as 0.001 that of the electron. In this talk, I will motivate the possible existence of milli-charged particles via kinetic mixing portals, discuss their current experimental state, and give an overview of this exciting new proposal.
Results of searches for both prompt and non-prompt leptonic decays of new
dark sector particles in proton-proton collisions with the ATLAS detector
are presented. Searches that encompass a wide range of new particle masses,
lifetimes and degrees of collimation of leptonic decay products are discussed.
The results are interpreted in the context of models containing new gauge
bosons (dark photons or dark Z bosons) that give rise to lepton-jets or to
more general displaced leptonic signatures that could be a viable dark matter
candidate.
The idea that dark matter forms part of a larger dark sector is very intriguing, given the high degree of complexity of the visible sector. In this talk, we discuss lepton jets as a promising signature of an extended dark sector. As a simple toy model, we consider an O(GeV) DM fermion coupled to a new U(1)′ gauge boson (dark photon) with a mass of order GeV and kinetically mixed with the Standard Model photon. Dark matter production at the LHC in this model is typically accompanied by collinear radiation of dark photons whose decay products can form lepton jets. We analyze the dynamics of collinear dark photon emission both analytically and numerically. In particular, we derive the dark photon energy spectrum using recursive analytic expressions, using Monte Carlo simulations in Pythia, and using an inverse Mellin transform to obtain the spectrum from its moments. In the second part of the talk, we simulate the expected lepton jet signatures from radiating dark matter at the LHC, carefully taking into account the various dark photon decay modes and allowing for both prompt and displaced decays. Using these simulations, we recast two existing ATLAS lepton jet searches to significantly restrict the parameter space of extended dark sector models, and we compute the expected sensitivity of future LHC searches.
The renormalizable coloron model, which has previously been shown in the literature to be
consistent with a wide array of theoretical and precision electroweak constraints, includes a pair of spinless bosons (one scalar, one pseudoscalar). We show that either of them, or both together if they are degenerate, could be responsible for the diphoton resonance signal for which both CMS and ATLAS have seen evidence. Because either of these bosons would be produced and decay through loops of spectator fermions, the absence of signals in dijet, t?t, and electroweak boson pair channels is not a surprise.
I will discuss the phenomenology of models in which the 750 GeV diphoton excess seen by ATLAS and CMS originates in a spin-0 resonance mostly coupled to electroweak gauge fields.
The grand unified group $E_6$ is a predictive scheme for physics beyond the
standard model (SM). It offers the possibility of extra Z bosons, new vector-like
fermions, sterile neutrinos, and neutral scalars in addition to the SM
Higgs boson. We discuss the Relevance of previous discussions of these features to a 750 GeV di-photon enhancement, recently observed by the ATLAS and CMS Collaborations at the CERN Large Hadron Collider.
In both scotogenic neutrino and flavor dark matter models, the dark sector communicates with the standard model fermions via Yukawa portal couplings. We propose an economic scenario that scotogenic neutrino and flavored mediator share the same inert Higgs doublet and all are charged under a hidden gauged U(1) symmetry. The dark Z2 symmetry in dark sector is regarded as the remnant of this hidden U(1) symmetry breaking. In particular, we investigate a dark U(1)D (and also U(1)B−L) model which unifies scotogenic neutrino and top-flavored mediator. Thus dark tops and dark neutrinos are the standard model fermion partners, and the dark matter could be inert Higgs or the lightest dark neutrino. We note that this model has rich collider signatures on dark tops, inert Higgs and Z′ gauge boson. Moreover, the scalar associated to the U(1)D (and also U(1)B−L) symmetry breaking could explain the 750 GeV diphoton excess reported by ATLAS and CMS recently.
I discuss an explanation for the diphoton excess which was recently reported by the experimental collaborations. Unlike conventional interpretations in which a new, heavy resonance of 750 GeV directly decays into a pair of photons, the explanation is based on a heavier resonance involving more complicated decays. I also emphasize that this way of interpretation is not restricted to the 750 GeV excess, but applicable to resonance-like signatures which would arise in the future.
I will discuss the question how a new Higgs boson related to the breaking of a new local symmetry in nature can lead to the observed excess in the di-photon channel. The numerical value of the di-photon rate implies an upper bound for the breaking scale of this new symmetry. The model predicts the existence of a new scalar field, which is stabilized by the remnant $Z_2$ after the gauge symmetry breaking and turns out to be an excellent dark matter candidate.
The model in question has three concrete realizations which can be distinguished experimentally as all provide different branching ratios of the new 750 GeV Higgs. A key feature of the models is the existence of a new force carrier, which is within the reach of the LHC experiment. The talk is based on 1604.05319.
In light of the recent 750 GeV diphoton excesses reported by the ATLAS and CMS collaborations, we investigate the possibility of explaining this excess using the
Minimal Dilaton Model. We find that this model is able to explain the observed excess with the presence of additional top partner(s), with same charge as the top quark, but with mass in the TeV region. We constrain model parameters using precision electroweak tests, single top production measurements, as well as Higgs signal strength data collected in the earlier runs of the LHC.
A novel model embedding the two Higgs doublets in the popular two Higgs doublet models
into a doublet of a non-abelian gauge group $SU(2)_H$ is presented.
The Standard Model $SU(2)_L$ right-handed fermion singlets are paired up with new heavy fermions to form $SU(2)_H$ doublets,
while $SU(2)_L$ left-handed fermion doublets are singlets under $SU(2)_H$.
Two of distinctive features of this anomaly-free model are:
(1) Electroweak symmetry breaking is induced from spontaneous symmetry breaking of $SU(2)_H$ via its triplet vacuum expectation value;
(2) One of the Higgs doublet can be inert, with its neutral component being
a dark matter candidate as protected by the $SU(2)_H$ gauge symmetry and Lorentz invariance instead of an ad hoc $Z_2$ symmetry.
I will discuss the model implications on collider constraints, Higgs physics, bounds from the electroweak precision data and dark matter relic density.
In addition, this model can account for the LHC 750 GeV diphoton anomaly as well as the muon g-2 with the help of the heavy fermions and an $SU(2)_H$ scalar doublet.
Neutrino oscillations are described by the Hamiltonian, $H=\frac1{2E}M$ where $M\equiv$diag$(0,\Delta m^2_{21},\Delta m^2_{31})$ and $\Delta m^2_{ij}\equiv m^2_i-m^2_j$.
Based on solar, atmospheric, and now reactor neutrino data, we know that the mass basis is very different from the flavor basis.
The two can be related by the unitary PMNS matrix, $U$, which is a function of three mixing angles conventionally known as $(\theta_{12},\theta_{13},\theta_{23})$ and one $CP$ violating phase $\delta$.
In matter, neutrinos experience an additional contribution to the Hamiltonian that acts on the electron eigenstate differently from the other two.
Combining this gives the full Hamiltonian in matter, $H=\frac1{2E}(UMU^\dagger+A)$ where $A=$diag$(a,0,0)$ and $a\equiv2\sqrt2G_FN_eE$ is the matter potential.
While it is possible to write down the eigenvalues, angles, and transition probabilities in matter exactly, the solutions are extremely complicated and offer no compelling insights.
Instead, we consider a perturbative approach to write analytic solutions to the full three flavor problem in a useful way, while still maintaining a high degree of accuracy.
To do this, we start with an expansion parameter $\epsilon\approx\Delta m^2_{21}/\Delta m^2_{31}\approx3\%$ that is replaced by an even smaller expansion parameter that is zero in vacuum and at most $\approx1.5\%$.
To address the two level crossings in the eigenvalues, we perform two rotations to a new basis.
These rotations are described by angles that correspond to $\theta_{12}$ and $\theta_{13}$ in matter.
$\theta_{23}$ and $\delta$ remain unchanged.
In this new basis, we show that the eigenvalues and the oscillation probabilities to first order are extremely accurate.
Moreover, they are also exact for $a=0$, the vacuum case.
Evaluating the eigenvalues and probabilities in various limits, $\{a,\sin\theta_{13},\Delta m^2_{21}\}\to0$ or $|a|\to\infty$ with the exact solution to the Hamiltonian is highly nontrivial, while it is straightforward to take limits of our perturbative expansion, and the limits are exact.
We also elect to maintain the simplest $L/E$ structure in the transition probabilities by using the minimal number of $L/E$ functions allowed.
Finally, while the expressions to second order are no longer compact, we numerically show how their precision far surpasses that obtainable by even the most optimistic of future experiments.
Coherent elastic neutrino-nucleus scattering (CE𝜈NS) is a long-standing prediction of the Standard Model. The possibility exists that new ultra-low energy threshold Si and Ge detectors will soon be able to observe the CE𝜈NS process with large statistics, potentially opening a new mode for probing neutrino physics and astrophysics beyond the Standard Model. This presentation will adopt the context of a specific and contemporary reactor-based experimental proposal (MI𝜈ER Collaboration), developed in cooperation with the Nuclear Science Center at Texas A&M University, referencing available technology based upon economical and scalable detector arrays. For expected exposures, sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC search with low mass detectors in the near term. This technology is also able to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. Leveraging a short meter-order experimental baseline and mobile reactor core, sensitivity is also available to first/fourth neutrino oscillation with a mass gap $\Delta m^2 \sim 1~{\rm eV}^2$ at an amplitude $\sin^2 2\theta \sim 10^{-2}$, or $\Delta m^2 \sim~0.1~{\rm eV}^2$ at unit amplitude. The combination of Si and Ge detectors facilitates discrimination between classes of models of new physics, and works together with variation of the propagation length to suppress leading correlated systematic uncertainties.
Understanding the charged current quasielestic (CCQE) neutrino-nucleus interaction is important for precision studies of neutrino oscillations. The theoretical description of the interaction depends on the combination of a nuclear model with the knowledge of form factors. While the former has received considerable attention, the latter, in particular the axial form factor, is implemented using the historical dipole model. Instead, we use a model-independent approach, presented in a previous study, to analyze the muon antineutrino CCQE mineral oil data published by the MiniBooNE collaboration. We combine the cross section for scattering of antineutrinos off protons in carbon and hydrogen, using the same axial form factor for both. The extracted value of the axial mass parameter $m_A = 0.84^{+0.12}_{-0.04} \pm {0.11} \, {\rm GeV}$ is in very good agreement with the model-independent value extracted from MiniBooNE's neutrino data. Going beyond a one-parameter description of the axial form factor, we extract values of the axial form factor in the range of $Q^2=0.1...1.0$ GeV$^2$, finding a very good agreement with the analogous extraction from the neutrino data. We discuss the implications of these results.
We are entering a new era of neutrino astronomy with the recent IceCube discovery of high-energy astrophysical neutrinos. Important questions, such as what their sources are, arise with these events. The flavor composition of these neutrinos has been identified as a rich observable, containing information about the production processes and neutrino properties. So far, only νμ charged current interactions can be uniquely identified in IceCube. We propose new methods that can help identify ντ events. Our method could significantly enhance the IceCube flavor measurement sensitivity, making it possible to tell if new physics is required to explain the flavor composition.
There are two important missing pieces in the standard three neutrino oscillation framework: The neutrino mass ordering and to establish whether there is CP violation in the leptonic sector. Future neutrino oscillation facilities are being planned to finally determine both unknowns. At the same time, new physics in the form of Non-Standard neutrino Interactions (NSI) can be probed in long-baseline neutrino experiments. In fact, current neutrino oscillation data allows NSI couplings to be 'large' (of the order one compare to the Fermi constant). In this talk I will focus on the determination of the leptonic CP phase by running long-baseline neutrino oscillation experiments (T2K and NOvA) in presence of NSI. I will also discuss the implications of our results for the future neutrino program.
We perform a model-independent analysis of the possible residual Klein and generalized CP symmetries associated with arbitrary lepton mixing angles in the case that there are three light Majorana neutrino species. This approach emphasizes the unique role of the Majorana phases and provides a useful framework in which to discuss the origin of the Dirac CP phase in scenarios with spontaneously broken flavor and generalized CP symmetries. The method is shown to reproduce known examples in the literature based on tribimaximal and bitrimaximal mixing patterns, and is used to investigate these issues for the case of a particular (GR1) golden ratio mixing pattern.
We construct a model with three twin neutrinos in light of the neutrino appearance excesses at LSND and MiniBooNE. The model, which includes a twin parity, naturally predicts identical lepton Yukawa structures in the Standard Model and the twin sectors. As a result, a universal mixing angle controls all three twin neutrino couplings to the Standard Model charged leptons. This mixing angle is predicted to be the ratio of the electroweak scale over the composite scale of the Higgs boson and has the right order of magnitude to fit the data. The heavy twin neutrinos decay within the experimental lengths into active neutrinos plus a long-lived Majoron and can provide a good fit, at around 4σ confidence level, to the LSND and MiniBooNE appearance data while simultaneously satisfying the disappearance constraints. For the Majorana neutrino case, the fact that neutrinos have a larger scattering cross section than anti-neutrinos provides a natural explanation to MiniBooNE's observation of a larger anti-neutrino appearance excess.
We revisited the theoretical implications of the study of the
so-called $D$-coefficient which is a P-conserving and T-violating
correlation in the polarized neutron beta decay. While existing
literature argued that any operator that generates this coefficient
will inevitably generate various electric dipole moments in loop
level and the latter set a much stringent bound than the direct
detection, we pointed out that there exists a class of dimension-6
operators involving right-handed neutrinos that contribute to this
correlation in second order and receive no stringent bound from
current upper bounds of electric dipole moments. Assuming a natural
size of the dimensionless Wilson coefficients, the current upper
bound on the neutron $D$-coefficient implies a new physics scale of
$\Lambda>1$TeV.
A search for supersymmetry with gauge mediated breaking is presented. This search was carried out in pp-collisions with two photons collected by the CMS Experiment at the LHC, CERN at $\sqrt{s}=13$ TeV with integrated luminosity of 2.3 fb^{-1}. The missing transverse energy of the selected events was then compared with the Standard Model background predictions which were determined using a data-driven technique. The results were then interpreted using the simplified models.
We discuss resonant squark production at the LHC via baryonic R-parity violating interactions. The cross section easily exceeds pair-production and a new set of signatures can be used to probe squarks, particularly stops. These include dijet resonances, same-sign top quarks and four-jet resonances with large b-jet multiplicities, as well as the possibility of displaced neutralino decays. We use publicly available searches at $\sqrt s=$8 TeV and first results from collisions at $\sqrt s=$13 TeV to set upper limits on R-parity violating couplings, with particular focus on simplified models with light stops and neutralinos. The exclusion reach of these signatures is comparable to R-parity-conserving searches, $m_{\tilde t}\simeq$500–700 GeV. In addition, we find that O(1) couplings involving the stop can be excluded well into the multi-TeV range, and stress that searches for single- and pair-produced four-jet resonances will be necessary to exclude sub-TeV stops for a natural SUSY spectrum with light higgsinos.
A review of the latest results on SUSY searches for stops/sbottoms with the CMS detector with 13 TeV data.
Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the third generation quarks with masses not too far from those of their Standard Model counterparts, which would give rise to large production rates at the LHC. Several supersymmetric models also predict massive long-lived supersymmetric particles. If charged,
these might be directly detected through abnormal specific energy loss
and time-of-flight techniques. This talks presents recent ATLAS searches for direct production of top and bottom squarks and for long lived supersymmetric R-hadrons. Results from the analysis of 13 TeV proton-proton collisions will be presented.
In supersymmetric extensions of the Standard Model, the superpartners of the top quark (stops) play the crucial role in addressing the naturalness problem. For direct pair-production of stops with each stop decaying into a top quark plus the lightest neutralino, the standard stop searches have difficulty finding the stop for a compressed spectrum where the mass difference between the stop and the lightest neutralino is close to the top quark mass, because the events look too similar to the large $t\bar{t}$ background. With an additional hard ISR jet, the two neutralinos from the stop decays are boosted in the opposite direction and they can give rise to some missing transverse energy. This may be used to distinguish the stop decays from the backgrounds. In this paper we study the semileptonic decay of such signal events for the compressed mass spectrum. Although the neutrino from the $W$ decay also produces some missing transverse energy, its momentum can be reconstructed from the kinematic assumptions and mass-shell conditions. It can then be subtracted from the total missing transverse momentum to obtain the neutralino contribution. Because it suffers from less backgrounds, we show that the semileptonic decay channel has a better discovery reach than the fully hadronic decay channel along the compressed line $m_{\tilde{t}} - m_{\tilde{\chi}}\approx m_t$. With 300 $\text{fb}^{-1}$, the 13 TeV LHC can discover the stop up to 500 GeV, covering the most natural parameter space region.
Introduction
A minimal U(1)x extension of the MSSM
Bounds on Z'
Impact on stops masses
Conclusions
We study a supersymmetric extension of the MSSM that gives both a dark matter (DM) candidate and contributes to account for the 125 GeV Higgs mass. We show how to achieve excellent $\sim$ 10 % fine-tuning and a thermal relic WIMP DM consistent with all existing constraints, by just adding a pair of SU(2) doublets and a singlet to the MSSM. The main annihilation channels in our model are to $t\bar t$ and Higgsinos (the Higgsinos should be light in natural SUSY). We will see how the relic abundance and spin-dependent (SD) direct detection (DD) cross section are related. Therefore imposing the relic density constraint implies a particular value for the SD DD cross section. Fortunately, this value is not ruled out yet, but the next generation of DM experiments should completely rule out or discover this model.
Current data (LHC direct searches, Higgs mass, dark matter-related bounds) severely affect the constrained minimal SUSY standard model (CMSSM) with neutralinos as dark matter candidates. But the evidence for neutrino masses coming from oscillations requires extending the SM with at least right-handed neutrinos with a Dirac mass term. In turn, this implies extending the CMSSM with right-handed sneutrino superpartners, a scenario we dub $\tilde\nu$CMSSM. These additional states constitute alternative dark matter candidates of the superWIMP type, produced via the decay of the long-lived next-to-lightest SUSY particle (NLSP). Here we consider the interesting and likely case where the NLSP is a $\tilde\tau$: despite the modest extension with respect to the CMSSM this scenario has peculiar phenomenological signatures such as charged tracks. After taking into account the role played by neutrino mass bounds and the specific cosmological bounds from the big bang nucleosynthesis in selecting the viable parameter space, we discuss the excellent discovery prospects for this model at the future runs of the LHC.
The simplest extension of the Standard Model is to add a scalar singlet. The only renormalizable interactions with the SM are then through the Higgs boson. One interesting consequence of adding the scalar singlet is that there can be resonant double Higgs production. I will give an overview of these types of models with a specific emphasis on the enhancement of the double Higgs production rate. This will include a discussion of interference effects that can be substantial for heavy scalars and the stability of the enhanced production with respect to NLO QCD corrections.
Higgs pair production is not only interesting as a probe of the trilinear Higgs self-coupling but it can also help to constrain SM extensions. In this talk I will discuss the question whether New Physics might show up for the first time in Higgs pair production focusing on the gluon fusion production process. There is a plethora of New Physics phenomenology like new couplings, new loop particles or new resonances, that can show up in this process. Finally, I will comment on next-to leading order QCD corrections to Higgs pair production in the MSSM and in composite Higgs models with and without new vector-like fermions.
The study of the resonant production of Higgs boson (h) pairs represents an important way to test a broad range of models of physics beyond the standard model (BSM) and offers an unique way to explore the properties of the scalar sector.
The searches for resonances decaying into a pair of Higgs bosons with the CMS experiment will be presented in this talk. Both the results established with the data from pp collisions at a centre-of-mass energy of 7 and 8 TeV (Run I) and the latest results from 13 TeV collisions (Run II) will be presented. The talk will cover the analyses of different decay modes of the hh pair, that will be compared and interpreted in some of the main BSM models that motivate the search for hh resonant production.
I will review recently published results from the ATLAS Collaboration, focusing on di-Higgs final states and rare or exotic decays of the Higgs boson. Results will be based on either LHC Run 1 data or Run 2 data collected in 2015. Specific topics may include searches for resonant and non-resonant di-Higgs production in $b\bar{b}\gamma\gamma$ final states, di-Higgs production in $b\bar{b}b\bar{b}$ final states and lepton-flavor-violating decays of the Higgs boson.
The Twin Higgs model seeks to address the little hierarchy problem by making the Higgs a pseudo-Goldstone of a global $SU(4)$ symmetry that is spontaneously broken to $SU(3)$. Gauge and Yukawa couplings, which explicitly break $SU(4)$, enjoy a discrete $Z_2$ symmetry that accidentally maintains $SU(4)$ at the quadratic level and therefore keeps the Higgs light. However, making the Twin Higgs phenomenologically viable requires introducing a soft $Z_2$ breaking and tuning it against the $SU(4)$ breaking. We propose a model to alleviate this tuning, without the need for an explicit $Z_2$ breaking sector. The model consists of two $SU(4)$ fundamental Higgses, one whose vacuum preserves $Z_2$ and one whose vacuum breaks it. As the interactions between the two Higgses are turned on, the $Z_2$ breaking is transmitted from the broken to the unbroken sector and a small hierarchy of vevs is naturally produced. The presence of an effective tadpole and feedback between the two Higgses lead to a sizable improvement of the tuning. The resulting Higgs boson is naturally very Standard Model like.
Many models that explain naturalness introduce colored top partners to cancel the top quadratic divergence. These colored top partners modify SM rates of gluon fusion and Higgs decays to gg and \gamma\gamma. We present a model agnostic analysis of scalar,fermionic and vector top partners and discuss the potency of other BSM scenarios like invisible Higgs decays to hide these colored top partner signatures. We also present caveats that throw up model building challenges.
Many models of physics beyond the Standard Model (SM) contain enhanced couplings to third generation quarks. We present an overview of searches for new physics containing 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. These 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. This results in a top-pair-like final state, as the T decays to a W boson and bottom quark. We explore the use of jet substructure techniques to reconstruct the highly boosted objects in events, enhancing the sensitivity of these searches.
In the present talk the search for new resonances decaying to tt resonances, as well as the search for new vector-like quarks will be presented. The search is performed with the ATLAS experiment at the LHC using proton-proton collision data. The current status of the ATLAS searches in different topolo- gies will be reviewed, addressing the used analysis techniques, in particular the selection criteria, the background modelling and the related experimen- tal uncertainties. The phenomenological implications of the obtained results will also be discussed.
The heavy scalar resonance search channel of gg → S → tt is very challenging, caused by a large destructive interference with the SM background. We analyze the line shapes of heavy scalars in several well-motivated beyond the standard model physics models. Commonly existing additional contributions to the glu-glu-scalar coupling change the relative phases of the signal and background amplitudes, inducing new opportunities in this channel. In many cases, we also make connections with the corresponding indirect constraints from the observed light Higgs boson properties. We further outline various methods to improve the LHC search in this channel.
We present results of searches for massive 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 8 and 13 TeV. These fourth-generation vector-like quarks are postulated to solve the Hierarchy problem and stabilize the Higgs mass, while escaping constraints on the Higgs cross section measurement. The vector-like quark can be produced singly or in pair and their decays result in a variety of final states, containing top and bottom quarks, 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.
Fermionic and vector resonances are a generic prediction of theories where electroweak symmetry breaking is triggered by new strongly interacting dynamics at the TeV scale.
We work in a "discrete" two site prescription of the Composite Higgs model where the spontaneous breaking of the SO(5)/SO(4) coset gives the Standard Model gauge bosons and six heavy vector resonances. We implement a partially composite scenario for the top sector which gives us the 1/3, 2/3 and 5/3 charged top partners. The direct and indirect (electroweak and flavor precision) constraints and requirement of naturalness impose stronger bounds on the heavy vectors than the top partners. This mild hierarchy between the top partners and the heavy vector resonances modifies the search strategy for vector resonances at the LHC. We find that when kinematically allowed, decays of heavy vector resonances to top partners dominate over pure Standard Model final states. We focus on the decay modes where top partner is singly produced. As a part of the "no loose" strategy for heavy vector resonances, these signatures with strongly boosted tops need to be considered. These searches for top partners from vector resonances can aid in hunting top partners and also discover (exclude) vector resonances at the 13 TeV run of the LHC.
We assess current experimental constraints on the bi-doublet + singlet model of top compositeness previously proposed in the literature. This model extends the standard model's spectrum by adding a custodially-embedded vector-like electroweak bi-doublet of quarks and a vector-like electroweak singlet quark. While either of those states alone would make the model vulnerable to constraints from precision electroweak data, in combination they can produce a viable model. We show that current precision electroweak data, in the wake of the Higgs discovery, accommodate the model and we explore the impact of direct collider searches for the partners of the top quark.
We present the discovery potential for a TeV-scale $H^{\pm}$
though its decays to boosted heavy quarks ($pp\to t H^{\pm} + X\to t (tb) + X$).
In the alignment limit of a type-II two Higgs doublet model,
searches for $H^{\pm}$ effectively constrain its neutral siblings ($H/A$).
We tag massive $H^{\pm}\to t b$ by pairing a high-efficiency
boosted-top tag with our low fake-rate $\mu_x$ boosted bottom-jet
tag (which rejects high-$p_T^{}$ light jets ${\sim}10$ times better than prior
$b$~tags). The success of the $\mu_x$ tag to suppress QCD
background for $H^{\pm}$ events further validates its usefulness in the
high-$p_T^{}$ regime (as was already demonstrated in generic
$W^\prime$ and leptophobic $Z^\prime$ searches).
There are searches for a $W'$ through many different decay channels at the LHC. Here we study the search for the $W'$ in the decay channel $W' \to tb$, including the decay of the top, at NLO+NLL in QCD. When applying cuts to the events, it is important to have the most precise predictions for the kinematics of the final state particles. Resummation allows us to include the soft gluon effects on top and bottom quarks, which has large effects on some distributions, such as the transverse momentum of the top and bottom.
We present a novel dark matter candidate, an Elastically Decoupling Relic (ELDER), which is a cold thermal relic whose present abundance is determined by the cross-section of its elastic scattering on Standard Model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross-section with electrons, photons and/or neutrinos in the $10^{-3} − 1$ fb range.
In this talk I will go over a new mechanism for setting the relic abundance of a thermal dark matter candidate. Unlike the usual WIMP paradigm, the abundance is set without chemical equilibrium between the Standard Model and the dark sector at freeze-out. The premise is to consider multiple degenerate particles in the dark sector, with a subset of those particles decaying to the visible sector. These “co-decays” set the relic density of the stable particles, which is determined by the usual thermally-averaged cross section but with an additional ingredient: the decay rate. Interestingly, the density of the dark matter candidate is no longer Boltzmann suppressed but has a novel scaling. Such scenarios can be realized in realistic models with broken symmetries. To demonstrate this I will present a plausible model for the dark sector.
In this talk, I will present a dark matter model in which both the dark sector and the visible sector share a common asymmetry. This asymmetry is mediated by an unstable dark particle of baryon number one through a semi-annihilation process. We realize a viable parameter space in which we find (1) the correct dark matter abundance, (2) the correct baryon asymmetry, and (3) a plausible dark matter interpretation for the Fermi GeV excess. This model provides a proof-of-concept that fully asymmetric dark matter can still lead to interesting indirect detection signals.
Of the three notable exceptions to the standard calculation of dark matter freezeout, namely co-annihilation, resonant annihilation and forbidden annihilation, the third is the least explored in the literature. Here DM annihilates to states heavier than itself, therefore the thermal annihilation cross-section is set by averaging over the tail of its velocity distribution. (At zero temperature, this process is kinematically forbidden.) We construct simplified DM models to verify and demonstrate the feasibility of "forbidden WIMPs": weak scale DM annihilating to SM final states. Relevant limits and prospects will be presented.
Besides solving the hierarchy problem by introducing an SM-neutral twin sector (hidden naturalness), Twin Higgs models naturally furnish a WIMP-like dark matter (DM) scenario with an attractive DM candidate ${}-{}$ the lightest twin charged lepton. The twin particle spectrum contains light twin particles, including the twin-photon and neutrinos, that are customarily assumed to be either heavy or altogether absent in order to bypass cosmological constraints on the dark radiation (DR). As we will demonstrate in this talk, however, the existence of light twin particles can in fact resolve various large- and small-scale structure puzzles while still fulfilling current cosmological constraints.
We will discuss an example of a minimal Twin Higgs scenario in the Fraternal Twin Higgs model with the twin tau playing the role of the DM. We take twin-neutrinos to be self-interacting DR coupled through a gauged U$(1)_{B-L}$ symmetry in the twin sector. We find that the twin-tau self-interaction through twin-photon exchange can address anomalies related to halo structures. Further, the twin-tau/twin-neutrino interaction provides a mechanism for damping the large scale structure power spectrum and an explanation for the $\sigma_8$ discrepancy between the CMB and weak lensing measurements.
Dynamical Dark Matter (DDM) is a new frame work for dark-matter physics that relies on a balancing between decay widths and abundances across a vast ensemble of particle species which collectively constitute the dark-matter candidate. Such a balancing can be achieved in broad variety of ways; however, only a small number of these possibilities have thus far been explored in the literature. Indeed, previous studies have focused on a particular class of DDM ensembles--motivated primarily by Kaluza-Klein towers in theories with extra dimensions--for which the density of states behaves roughly as a polynomial of the mass of the state. By contrast, in this paper, we study the properties of a different class of DDM ensembles for which the density of states grows exponentially with the mass of the state. The canonical example of such an ensemble is a collection of “hadronic” resonances associated with the confining phase of a strongly-coupled dark sector. We demonstrate how an appropriate balancing between decay widths and abundances can naturally arise for such ensembles, despite this exponential rise in the density of states, and investigate how their properties are constrained by observational data.
In non-minimal dark-matter models such as Dynamical Dark Matter (DDM), the mass spectrum of the dark-sector states plays a crucial role in dark-matter phenomenology. In this talk, I examine one natural method in which a particularly auspicious mass spectrum can be generated for an ensemble of such states via early-universe processes which are essentially random. Despite this inherent randomness, a characteristic mass spectrum statistically emerges in which the density of states for the ensemble decreases in a predictable way as a function of mass. I discuss the phenomenological implications of such "emergent" mass spectra within the DDM framework and explore some of the possibilities for model-building to which they give rise.
We demonstrate that multi-component scalar ensembles in the early universe can experience a variety of surprising phenomena when subject to a cosmological mass-generating phase transition. These include severe suppressions to their late-time cosmological (relic) abundance, parametrically resonant enhancements, re-distribution of energy density across the ensemble, and a ``re-overdamping'' effect which causes the total energy density to behave in ways that differ from those exhibited by pure dark matter or vacuum energy. Furthermore, in the case of scalar KK models, we find that the tower of KK states becomes self-limiting, i.e. the abundance of higher-mass components is hugely suppressed so that the tower becomes effectively finite. Additionally, we find that modifications in both the total abundance and its distribution varies substantially throughout the model parameter space. These results could have significant implications for cosmological moduli, axion-like particles, or any models with scalar KK towers that undergo mass-generating phase transitions.
We present a summary of searches for new physics with non-resonant high mass signatures.
The talk focuses on W' and extra dimension models in mono lepton, dijet and multi particle final states using 2015 CMS data at $\sqrt{s}=13\,\mathrm{TeV}$.
A search for quark contact interactions and extra spatial dimensions in dijet angular distributions in proton proton collisions at 13 TeV is presented. The data was collected by CMS detector at the CERN LHC and corresponds to an integrated luminosity of 2.6 fb-1. The measured distributions are found to be in good agreement with predictions from perturbative QCD that include electroweak corrections. Limits for different contact interaction models are obtained. In a benchmark scenario, where only left-handed quark participate and which is evaluated to leading-order in QCD, quark contact interactions are excluded up to 12.1 (16.3) TeV for destructive (constructive) interference at 95% confidential level. Lower limits between 7.7 and 10.8 TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed–Dimopoulos–Dvali model of extra spatial dimensions.
We present holographic Randall-Sundrum like models of spontaneously broken conformal symmetry that realize a light dilaton and suppressed cosmological constant from condensates. A ''soft-wall'' realization of the RS geometry is generic in such cases, where the IR brane plays a lesser role as a cutoff for large curvature effects, and low energy observables such as the spectrum of states are largely insensitive to its position. Large hierarchies are easier to realize as the stabilizing term in the dilaton potential is automatically suppressed by a small Goldberger-Wise scalar mass. We also present analysis of the model at finite temperature.
In the context of a simple gauge-Higgs unification (GHU) scenario based on the gauge group SU(3)×U(1)′ in a 5-dimensional flat space-time, we investigate a possibility to reproduce the observed Higgs boson mass of around 125 GeV. We introduce bulk fermion multiplets with a bulk mass and a (half) periodic boundary condition. In our analysis, we adopt a low energy effective theoretical approach of the GHU scenario, where the running Higgs quartic coupling is required to vanish at the compactification scale. Under this "gauge-Higgs condition," we investigate the renormalization group evolution of the Higgs quartic coupling and find a relation between the bulk mass and the compactification scale so as to reproduce the 125 GeV Higgs boson mass. Through quantum corrections at the one-loop level, the bulk fermions contribute to the Higgs boson production and decay processes and deviate the Higgs boson signal strengths at the Large Hadron Collider (LHC) experiments from the Standard Model (SM) predictions. Employing the current experimental data which show the the Higgs boson signal strengths for a variety of Higgs decay modes are consistent with the SM predictions, we obtain lower mass bounds on the lightest mode of the bulk fermions.
Warped extra dimensions can address both the Planck-weak and flavor hierarchies of the Standard
Model (SM). In this paper we discuss the SM neutrino mass generation in a scenario in which a SM
singlet bulk fermion — coupled to the Higgs and the lepton doublet near the IR brane — is given
a Majorana mass of order the Planck scale on the UV brane. Despite the resemblance to a type I
seesaw mechanism, a careful investigation based on the mass basis for the singlet 4D modes reveals
a very different picture. Namely, the SM neutrino masses are generated dominantly by the exchange
of the TeV-scale mass eigenstates of the singlet, that are pseudo-Dirac and have a sizable Higgs-
induced mixing with the SM doublet neutrino: remarkably, in warped 5D models the anticipated
type I seesaw morphs into a natural realization of the so-called “inverse” seesaw. This understanding
uncovers an intriguing and direct link between neutrino mass generation (and possibly leptogenesis)
and TeV-scale physics. We also perform estimates using the dual CFT picture of our framework,
which back-up our 5D calculation.
Recently, it was shown that a canonical implementation of the type I seesaw mechanism in a warped extra dimensional framework is in reality a natural realization of ``inverse" seesaw, i.e., the SM neutrino mass is dominantly generated by exchange of pseudo-Dirac weak-scale SM singlet neutrinos. We study signals from production of these heavy singlet neutrinos at the LHC, using the elementary-composite site parametrization of this model.
The composite gauge symmetry is assumed to be $SU(2)_L \times SU(2)_R \times U(1)_X$, with singlet neutrino being part of a doublet of $SU(2)_R$, thus charged under $W_R$ and produced in its decays (similarly to 4D left-right (LR) symmetric models).
Naively, the direct coupling of light quarks to $W_R$ is negligible, because former is elementary, while latter is composite. However, due to almost degeneracy of mass of composite $W_L$ and $W_R$, we could obtain maximal mixing between these two after electro-weak symmetry breaking (EWSB), and thus on-shell production of $W_R$ at hadron colliders becomes feasible. Also, because of compositeness of the relevant particles, the dominant decay channel for $W_R$ involves the singlet neutrino and its $SU(2)_R$ doublet partner, i.e., a composite electron (instead of SM electron in 4D LR models). In turn, singlet neutrino can decay (as usual) into SM electron and W, while
the composite electron gives SM Higgs/Z and SM electron.
We show that a signal of large enough significance is possible at the 14 TeV LHC with 300 $\textrm{fb}^{-1}$ in the final states $l^{\pm} l^{\mp} j j H$ and $l^{\pm} l^{\mp} l^{\pm} H + \textrm{MET}$.
Furthermore, the singlet neutrino can also be pair produced via $Z^{ \prime }$ (the gauge boson of composite U(1) which is orthogonal to composite U(1)Y), following a similar mixing with composite Z from EWSB. Besides, it is possible that singlet neutrinos can come from decays of composite partners of $SU(2)_L$ doublet leptons, which are absent in the 4D LR case. These possibilities might become relevant for the even higher luminosity run of the LHC.
Physics at future colliders
The physics prospects at the LHC luminosity upgrade of LHC, HL-LHC,
with 300 and 3000 fb-1 of data simulated in the ATLAS detector are
presented and discussed.
The ultimate precision attainable on measurements of the couplings of
the 125 GeV boson to elementary fermions and bosons is discussed, as
well as perspectives on the searches for partners associated with it.
The electroweak sector is further studied with the analysis of the
vector boson scattering, testing the SM predictions.
Supersymmetry is one of the best motivated extensions of the Standard
Model. The current searches at the LHC have yielded sensitivity to TeV
scale gluinos and 1st and 2nd generation squarks, as well as to 3rd
generation squarks and electro-weakinos in the hundreds of GeV mass
range. Benchmark studies are presented to show how the sensitivity
improves at the future LHC runs. The prospects of searches for new
heavy bosons and dark matter candidates at 14 TeV are explored as well
as the sensitivity of searches for anomalous top decays.
For all these studies, a parameterised simulation of the upgraded
ATLAS detector is used, taking into account the expected pileup
conditions.
We study the correlation between the value of the hZZ coupling and the nature of the electroweak phase transition. We consider a singlet extension of the SM to study the correlation of the hZZ coupling and the first order phase transition. Furthermore, we study how the further colliders, for example CEPC and ILC, can probe the precision hZZ coupling.
The productions of double SM-like Higgs bosons at the future colliders, such as CEPC/ILC and SppC, will play a crucial role in determining the SM-like Higgs self couplings. In this talk, I will present our recent project in searching for the SM-like Higgs boson pairs at the CEPC/ILC. We will compare the search potentials for this process at different C.O.M. energies, namely, at CEPC 400 GeV/500 GeV, and also ILC 500 GeV. Besides, we will briefly comment on the SppC searches for the heavy resonance via the double SM-like Higgs boson final states.
We propose a measurement of the top Yukawa coupling at a 100 TeV hadron collider, based on boosted Higgs and top decays. We find that the top Yukawa coupling can be measured to 1%, with excellent handles for reducing systematic and theoretical uncertainties, both from side bands and from $t\bar{t}H / t\bar{t}Z$ ratios.
The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Among recent results are the measurement of Z event shape observables sensitive to the modelling of the underlying event, and the measurement of diffractive dijet production with a large rapidity gap, which tests the interplay of soft and hard phenomena. The total pp cross section, a fundamental property of the strong interaction, is explored via measurements of the elastic pp cross section and the total inelastic cross section at cms energies of 7,8 and 13TeV. Precision measurements of the isolated high pT inclusive photon cross section at cms energies of 8TeV and 13TeV test the theoretical predictions and constrain parton density functions. An overview of these results is given.
I will talk about the importance of boosted jets and jet substructure at the LHC. Then, I will make a comparison between techniques that discriminate two-pronged signals from QCD background using constraints on energy flow within boosted jets. To that aim, I focus on three commonly-used jet shapes: N-subjettiness, the mass-drop parameter and energy-correlation functions. I will show that we can understand their performance from first-principle QCD calculations and also compare the results with Monte-Carlo simulations.
Our group studied the low-lying hadron spectrum of lattice QCD on a large $32^3 \times 256$
anisotropic space-time lattice at a near-physical pion mass of $240$ MeV.
Quark fields were smeared using a
Laplacian Heaviside kernel which is later exploited to estimate quark
propagation with a novel method: the Dirac matrix-inverse is stochastically
estimated by introducing noise vectors in the Laplacian Heaviside subspace.
Interpolating operators expected to overlap
with single- and two-particle meson and baryon states were used,
staying below the three-particle energy threshold.
Preliminary results for the $I = 1, S = 0, T_{1 u}^+$ channel
will be shown, along with other channels.
The Luescher method has been applied to the two-particle finite-volume
spectrum to obtain results for the phase shift and width
of the $\rho$. Future work will briefly be discussed, which includes
an alternative to the Luescher method involving an effective finite-volume
Hamiltonian to fit the spectrum, and the implementation of tetraquark operators
with fundamental (and higher) gauge-links.
The proton radius puzzle challenges our understanding of the structure of the proton. It can be an indication of a new force that couples to muons, but not to electrons. An effective field theory analysis using Non-Relativistic Quantum Electrodynamics (NRQED) indicates that the muonic hydrogen result can in interpreted as a large, muon-proton spin-independent contact interaction. The muonic hydrogen result can be tested by a muon-proton scattering experiment, MUSE, that is planned at the Paul Scherrer Institute. The typical momenta of the muons in this experiment are of the order of the muon mass. In this energy regime the muons are relativistic but the protons are still non-relativistic. The interaction between the muons and protons can be described by a hybrid QED-NRQED effective field theory. We present some elements of this effective field theory, and compare them previously known results.
TeV-scale new physics addressing the hierarchy problem can leave imprints on precision observables. In the absence of new light states, effective field theories (EFT) provide a consistent framework to characterize deviations from the Standard Model that is completely general. On the other hand, the historically influential oblique parameters (most notably S, T parameters) formalism is generally speaking only applicable to a restricted class of new physics scenarios known as universal theories. I will discuss the reconciliation of the two approaches by presenting an EFT description of universal theories, and clarify some issues regarding consistent use of oblique parameters in precision electroweak analyses.
The talk will summarize recent measurements of multi-boson production by the
ATLAS Collaboration.
Vector boson production in pp collisions at 7, 8 and 13 TeV has been extensively studied by ATLAS. Recent results include the precision measurements of the transverse momentum of the Z/gamma* boson production, sensitive to soft resummation effects, hard jet emissions and electroweak corrections. A precise measurement of the angular coefficients of the Zboson production tests the underlying QCD dynamics of the DrellYan process. A first measurement of the inclusive W and Z cross section at a cms energy of 13TeV has been derived.
The Production of jets in association with a vector boson is an important process to study QCD in a multiscale environment. Cross sections, differential in several kinematics variables, have been measured with the ATLAS detector and compared to stateoftheart QCD calculations and Monte Carlo simulations. First measurements of vector boson + jets production have been performed at cms energies of 13TeV. An overview of these results is given.
I shall present scalar extensions of the Standard Model motivated by neutrino mass and dark matter, where radiative electroweak symmetry breaking occurs naturally.
Expanding the Standard Model(SM) through the incorporation of L-R symmetric gauge extension that exhibits conformal invariance at the classical level, it is possible to remedy the Higgs vacuum instability problem. The model includes a $SU(3)_C$×$SU(2)_L$×$SU(2)_R$×U(1)$_B$$_-$$_L$ gauge group, Higgs bi-doublet which includes the SM Higgs, and a $SU(2)_R$ scalar doublet field. The Coleman-Weinberg mechanism radiatively breaks $SU(2)_R$×U(1)$_B$$_-$$_L$ down to $U(1)_Y$. This $SU(2)_R$ VEV in turn produces a negative mass$^2$ coupling to the Higgs bi-doublet field which results in Electro-Weak Symmetry Breaking. On the pretext of solving the Higgs vacuum instability problem, a viable parameter region is found such that the vacuum remains stable. Within this parameter region the naturalness of the theory is investigated. As the heavy gauge bosons from the $SU(2)_R$×U(1)$_B$$_-$$_L$ breaking contribute to the Higgs mass corrections, there must be a bound on these contributions so as to avoid a fine tuning scenario at the Electro-Weak scale. These heavy gauge bosons are within the reach of LHC run 2 in the coming future.
Several radiative neutrino mass models will be considered. In the first model, a variation of the well known 2006 Scotogenic radiative seesaw model of neutrino mass will be discussed in which Standard Model (SM) is extended with Majorana Fermions, real singlet scalars, and a set of doublet fermions to realize the notion of the inverse seesaw neutrino mass naturally. The lightest of the real scalars through which neutrino masses are generated is protected by discrete $Z_2$ symmetry and is a possible Dark Matter (DM) candidate.
In the other model, scalar triplet extension of the SM is considered. Lepton number symmetry is implemented to generated neutrino masses radiatively through the interaction of scalar triplet, neutrinos, and DM with a soft breaking of the Lepton number symmetry to $(-1)^L$. Interesting phenomenological implications of this model will be discussed.
In my talk I will discuss the relation between lepton number violation at high and low energies, particularly, the constraints on baryogenesis models obtained from an observation of neutrinoless double beta decay. Effective lepton number violating operators, which can underlie neutrinoless double beta decay, would together with sphaleron processes wash out a primordial (baryon) asymmetry (of the universe). Typically, if a mechanism of neutrinoless double beta decay other than the standard light neutrino exchange is observed, the usual scenarios of high-scale baryogenesis will be excluded. This can be experimentally achieved by different methods, e.g. through the observation of neutrinoless double beta decay in multiple isotopes or the measurement of the decay distribution. Apart from the effective field approach, I will also outline the possible extension of our arguments to a general UV-completed model.
We discuss the aspects of CP-violating effects on electroweak baryogensis in models where an extra Higgs doublet, a singlet and electroweak-interacting fermions are added. It is found that one CP-phase that directly relates the baryon asymmetry of the Universe (BAU) to the electric dipole moment (EDM) exists. Moreover, it is obtained that the parameter region for the successful BAU can be verified by the electron EDM in near future.
We prove that for a given operator in the SM with baryon number B and lepton number L, that the operator's dimension is even (odd) if (B-L)/2 is even (odd). Consequently, this establishes the veracity of statements that were long observed or expected to be true, but not proven, e.g., operators with B-L=0 are of even dimension, B-L must be an even number, etc. These results remain true even if the SM is augmented by any number of right-handed neutrinos with L=1.
Any new particle charged under $SU(3)_C$ and carrying electric charge will leave an imprint in the di-photon invariant mass spectrum as it can mediate $gg \to \gamma \gamma$ process through loops.
The combination of properties of loop functions and gluon pdfs results in a peak-like feature in the di-photon invariant mass around twice the mass of a given particle.
Using recent ATLAS analysis, we set upper limits on the combined $SU(3)_C$ and electric charge of new particles and indicate future prospects.
We briefly discuss the possibility that the excess of events in the di-photon invariant mass spectrum around 750 GeV originates from loops of a particle with mass around 375 GeV.
The Dark Matter (DM) nature remains one of the great puzzles of particle
physics; while we know that about 27% of the universe is in the form of
DM, little is known about its properties. If produced at the LHC, it should couple to the standard model though some mediator. The mediator can decay into dark
matter particles that escape the detector, leaving a large missing transverse
momentum (MET) as their signature. Also the mediator can decay into two quarks, which would appear as a bump in the invariant dijet mass spectrum. Recent results from ATLAS based on the presence of significant MET along with a variety of objects, and a dijet mass-spectrum analysis will be discussed.
CMS Mono-X (X=jet, V, photon, heavy flavors, etc.) searches will be discussed mainly.
The general strategy for dark matter (DM) searches at colliders currently relies on simplified models, which typically have a limited number of free parameters. In the case of $t$-channel colored mediators, these simplified models often have assumptions on the chirality of the DM-SM interactions with quarks, though generically a UV-complete model with such colored mediators would lead to the existence of more free parameters. In this study we look at the effect this broader set of free parameters has on direct detection and the mono-X + MET (X=jet,W,Z) signatures at 13 TeV LHC while maintaining gauge invariance of the simplified model under the
full SM gauge group. We find that the direct detection constraints require DM masses less than 10 GeV in order to produce phenomenologically interesting collider signatures. Additionally, for a fixed mono-W cross section it is possible to see very large differences in the mono-jet cross section when the usual simplified model assumptions are loosened and isospin violation between RH and LH DM-SM quark couplings are allowed.
See above
We present a complete phenomenological prospectus for thermal relic neutralinos. Including Sommerfeld enhancements to relic abundance and halo annihilation calculations, we obtain direct, indirect, and collider discovery prospects for all neutralinos with mass parameters M1, M2, |μ|<4 TeV, which freeze out to the observed dark matter abundance, with scalar superpartners decoupled. Much of the relic neutralino sector will be uncovered by the direct detection experiments Xenon1T and LZ, as well as indirect detection with Cerenkov Telescope Array. We emphasize that thermal relic Higgsinos will be found by next-generation direct detection experiments, so long as M1,2<4 TeV. Charged tracks at a 100 TeV hadron collider complement indirect searches for relic winos. Thermal relic bino-winos still evade all planned experiments, including disappearing charged-track searches. However, they can be discovered by compressed electroweakino searches at a 100 TeV collider, completing the full coverage of the relic neutralino surface.
We supplement the minimal supersymmetric standard model (MSSM) with vector-like copies of standard model particles. Such 4th generation fields can simultaneously increase the Bino mass without overclosing the universe, achieve the right Higgs mass with more natural superpartner masses and preserve gauge coupling unification. We verify that the model is safe from current bounds and discuss future sensitivity through collider searches and dark matter direct and indirect detection experiments.
We consider a concise dark matter scenario in the minimal gauged $B-L$ extension of the Standard Model (SM), where the global $B-L$ (baryon number minus lepton number) symmetry in the SM is gauged,
and three generations of right-handed neutrinos and a $B-L$ Higgs field are introduced.
Associated with the $B-L$ gauge symmetry breaking by a VEV of the $B-L$ Higgs field,
the seesaw mechanism for generating the neutrino mass is automatically implemented
after the electroweak symmetry breaking in the SM.
In this model context, we introduce a $Z_2$-parity and assign an odd parity
for one right-handed neutrino while even parities for the other fields.
Therefore, the dark matter candidate is identified as the right-handed Majorana neutrino with odd $Z_2$ parity,
keeping the minimality of the particle content intact.
When the dark matter particle communicates with the SM particles
mainly through the $B-L$ gauge boson ($Z^\prime_{BL}$ boson),
its relic abundance is determined by only three free parameters, the $B-L$ gauge coupling ($\alpha_{BL}$),
the $Z^\prime_{BL}$ boson mass ($m_{Z^\prime}$) and the dark matter mass ($m_{DM}$).
With the cosmological upper bound on the dark matter relic abundance
we find a lower bound on $\alpha_{BL}$ as a function of $m_{Z^\prime}$.
On the other hand, we interpret the recent LHC Run-2 results on search for $Z^\prime$ boson resonance
to an upper bound on $\alpha_{BL}$ as a function of $m_{Z^\prime}$.
Combining the two results we identify an allowed parameter region for this ``$Z^\prime_{BL}$ portal'' dark matter scenario,
which turns out to be a narrow window with the lower mass bound of $m_{Z^\prime} > 2.5$ TeV.
We investigate constraints on the interactions of light dark matter with Standard Model quarks in a framework with effective contact operators mediating the decay of heavy flavor bound state quarkonium to dark matter and a photon. When considered in combination with decays to purely invisible final states, constraints from heavy quarkonium decays at high intensity electron-positron colliders can complement missing energy searches at high energy colliders and provide sensitivity to dark matter masses difficult to probe at direct and indirect detection experiments. We calculate the approximate limits on the branching fraction for Y(1S) decays to dark matter and a photon. Given the approximate limits on the branching fractions for all dimension 6 or lower contact operators, we present the corresponding limits on the interaction strength for each operator and the inferred limits on dark matter-nucleon scattering. Complementary constraints on dark matter annihilation from gamma-ray searches from dwarf spheroidal galaxies are also considered.
I will describe a simple, well-motivated model based on a custodial symmetry which describes the tree-level production of a 750 GeV diphoton resonance from a decay of a singly produced vector-like quark. The model has several novel features. The identification of the resonance as an SU(2)$ _R $ triplet provides a symmetry explanation for suppression of its decays to hh, WW, and gg. Moreover, the ratio of the 13 TeV to 8 TeV cross sections can be larger than single production of a 750 GeV resonance, reaching ratios of up to 7 for TeV scale vector-like quark masses. This eliminates any tension between the results from Run I and Run II diphoton searches. The kinematic distributions from this new production mechanism are consistent with available experimental distributions in large regions of parameter space but, depending on the mass of the new vector-like quarks, can be differentiated from the background with more statistics.
I discuss the constraints implied by partial wave unitarity on new physics models explaining the LHC di-photon excess at 750 GeV. I argue that the effective description in terms of the SM supplemented by a single scalar resonance S breaks down at scales of few tens of TeV, where perturbative unitarity is violated due to the large cross-section required in order to fit the γγ signal. Likewise, I show that unitarity arguments can be used to set perturbativity bounds on renormalizable UV completions of the S-effective operators and discuss under which conditions the data can be accommodated within weakly-coupled models.
The 750 GeV diphoton resonance could be a heavy pion of a new strong dynamics sector with a confinement scale $\mathcal{O}(1 \text{ TeV})$. New fermions, vector-like under the strong dynamics group, are chiral under a new $U(1)^\prime$ gauge symmetry such that their masses are related to the $U(1)^\prime$-breaking scale or the confinement scale. Our model predicts a phenomenologically rich spectrum near the TeV scale, including a testable decay channel of the 750 GeV resonance into a photon plus $Z^\prime$ boson, which naturally has a large leptonic branching ratio.
1601.00006 Sunghoon Jung, Jeonghyeon Song, Yeo Woong Yoon
If the 750GeV diphoton excess is due to a scalar resonance produced via gg-fusion, the signal necessarily interferes with the continuum Standard Model background $gg\to \gamma \gamma$. The interference can not only change the resonance shape, but also enhance or suppress the excess rate. We take two representative examples exhibiting each effect and study how fit to the excess data changes. With 3-6 fb excess rate, the signal can be enhanced by 2-1.6, or the peak can be shifted by O(1) GeV (while overall shape is close to the Breit-Wigner). If the excess decreases in the future, the interference effects become relatively more significant and can provide non-trivial evidence/test of a scalar resonance hypothesis.
we revisit the model of a CP-even singlet scalar resonance, where the resonance appears as the lightest composite state made of scalar quarks participating in hidden strong dynamics. We show that the model can consistently explain the excess of diphoton events with an invariant mass around 750 GeV reported by both the ATLAS and CMS experiments. Due to inseparability of the dynamical scale and the mass of the resonance, the model also predicts signatures associated with the hidden dynamics such as leptons, jets along with multiple photons at future collider experiments. We also associate the TeV-scale dynamics behind the resonance with an explanation of dark matter.
We study dark matter physics of an axion-like bosonic portal model motivated by the recent report on the diphoton resonance at 750 GeV.
Identifying the resonance as the pseudo-scalar mediator between the standard model sector and dark matter sector, we could obtain profound implications to dark matter phenomenology from collider physics.
In this work, we fist find the preferred parameter region of the proposed model using the results of the LHC run at 13 TeV.
Next, we investigate the indirect signature of dark matter taking into account the data from various cosmic-ray searches including Fermi-LAT, HESS, and CTA.
We discuss a possible interpretation of the 750 GeV diphoton resonance, recently reported at the LHC, within a class of left-right symmetric models with gauge coupling unification. The unification is imposed by the underlying non-commutative geometry (NCG), which in these models is extended to a left-right symmetric completion of the Standard Model (SM). Within such unified left-right symmetric models the Higgs content is restrictively determined from the underlying NCG, instead of being arbitrarily selected as in canonical, non-unified, left-right symmetric models. We show that the observed cross sections involving the 750 GeV diphoton resonance could be realized through a SM singlet scalar field accompanied by colored scalars, present in these unified models. In view of this result we discuss the underlying rigidity of these models in the NCG framework and the wider implications of the NCG approach for physics beyond the SM.
In this talk, I will introduce the minimal toy model that explains recently observed 750GeV diphoton excess and its implication for the electric dipole moments of the neutron and electron. The model assumes that excess is due to a spin zero particle which couples to photons and gluons through the loops of massive vector-like fermions. In the plausible parameter space of the model, we can find electric dipole moments of the neutron and electron that are comparable to current experimental bounds. I will also provide the realistic model that contains composite pseudo-Nambu-Goldstone boson as the 750GeV resonance and its correspondence to previous toy model.
Lepton Flavour Universality is enforced in the Standard Model by construction. Any Violation
of LFU would be a clear sign of new physics. Existing hints of non universality are
already present in the leptonic and semileptonic decays of B mesons. The semitauonic decays in particular,
are sensitive to contributions from non-standard-model-particles that preferentially couple to
the third generation of fermions,the Higgs-like charged scalars. Also, electroweak penguin decays can be used to test lepton flavour universality between the first and the second leptonic families. This talk reports recent
studies of $B^0 \to D^* \tau \nu$ and $B^0 \to K^{(*)}ll$ decays at the LHCb experiment.
Probes of CP-violation in decays of Beauty-strange meson and a high sensitivity measurements of the rare Bs decays with the ATLAS detector, using Run1 data are presented. Highlights on the expected performance for Run2 will be shown.
ATLAS has a wide program to study the production properties of
conventional and exotic quarkonium, beauty, and charm bound states.
This presentation will cover the latest results on J/$\psi$, $\psi$(2s) and
$\Upsilon$ production at 7, 8, and 13 TeV, D meson and $\chi$(3872) production
with Run-1 data, B+ production at 13 TeV, and studies of associated
production of quarkonium with other heavy flavour states or vector
bosons. Latest results in the ATLAS program of heavy hadron
production and spectroscopy are also presented, including the latest
searches for the bottomonium counterpart to the $\chi$(3872), studies of
B$_c$ and $\Lambda_b$ decays, measurement of b-quark fragmentation
functions, and searches for new exotic bound states.
The discovery of the first pentaquark states and the first unambiguous
determination of the Zc(4430) as a tetraquark state achieved at LHCb in
the last years have incredibly increased the interest for exotic
hadrons containing heavy quarks. An overview of the
recent LHCb results on quarkonium-like hadrons is presented, including a study of the Bs 𝜋± system
We use e^+ e^- to 2 Jets and 3 Jets processes to study the fragmentation of B mesons and J/psi in identified jets with specific shapes (Angularities).
I will introduce the eletromagnetic decays of the $B_c(2S)$ meson, which is recently observed by the ATLAS. In the calculation, the instantaneous Bethe-Salpeter method is used, and our results show that the branching ratio of eletromagnetic decays of this particle is about $10\%$ of the whole decay width.
We will talk about the production of D-wave charmonia ($2^{-+}$, $2^{--}$, $3^{--}$) in the weak decays of $B_c$ meson. The wave functions of the heavy mesons are achieved by solving the instantaneous Bethe-Salpeter equation. The three-gluon decay processes of these charmonia are also investigated.
New electroweak states appear in generic extensions of the Standard Model but are challenging to discover at hadron colliders. When the lightest state in a new electroweak multiplet is neutral and all multiplet components are approximately degenerate, production of the charged components is followed by decay into nearly invisible states. If this decay occurs promptly, the only way to infer the presence of the reaction is through its missing energy signature. We propose using emission of photon radiation from these charged states as a means of discriminating the signal from SM backgrounds. We demonstrate the broad applicability of our technique by studying the cases of Higgsinos in natural supersymmetry and quintuplet fields.
Interesting features in high energy physics data can be determined from properties of Voronoi tessellations of the relevant phase space. We focus on the detection of kinematic "edges" in two dimensions, which may signal physics beyond the standard model. After deriving some useful geometric results for Voronoi tessellations on perfect grids, we propose several algorithms for tagging the Voronoi cells in the vicinity of kinematic edges in real data. In addition, we show that how Voronoi based methods help to find the available phase space boundary which can be utilized for mass measurement of new physics particles.
The lack of conclusive evidence for new physics in Run I of the LHC suggests that future discoveries may manifest themselves with small numbers of signal events. In this case, it will be crucial to use analysis techniques that extract as much information as possible from a limited number of events. Previously, a technique exploiting correlations in the full multi-particle phase space to efficiently reconstruct intermediate and invisible masses in decay chains has been demonstrated for the case of four final state particles. I will discuss the extension of this technique to decay chains with five or more final state particles and the structure of likelihood functions for arbitrary decay topologies.
If Supersymmetry (SUSY) is discovered at the LHC, it will be important to measure the masses and couplings as accurately as possible. Determining the precision with which the LHC can perform these measurements is important for understanding the road ahead, particularly in terms of complementarity between proposed colliders. We investigate the precision with which the gluino mass can be measured, in the context of radiative natural SUSY, using techniques of varying sophistication and robustness. As we are examining the gluino, our results have import implications for testing unification in the event of a SUSY discovery.
It is a possibility that the superworld (supersymmetric partners of our world) does exist without supersymmetry. The two worlds are being distinguished by an unbroken discrete Z_2 symmetry (similar to R-parity in supersymmetry). We lose the solution to the hierarchy problem. However, such a scenario has several motivations. For example, the lightest neutral superworld particle will be a candidate for dark matter. The other being, as in supersymmetry, it is possible to achieve gauge coupling unification. One major difference with the supersymmetric theory is that such a theory is much more general since it is not constrained by supersymmetry. For example, some of the gauge couplings connecting the Standard Model particles with the superpartners now become free Yukawa couplings. As a result, the final state signals as well as the limits on the superworld particles can be modified both qualitatively and quantitatively. The reach for these superworld particles at the Large Hadron Collider (LHC) can be much higher than the superpartners, leading to the increased possibility of discovering new physics at the LHC
Realizing that couplings related by supersymmetry (SUSY) can be disentangled when SUSY is broken, it is suggested that unwanted flavor and CP violating SUSY couplings may be suppressed via quenched gaugino-flavor interactions, which may be accomplished by power-law running of sfermion anomalous dimensions. A simple theoretical framework to accomplish this is exemplified and the defeated constraints are tallied. One key implication of the scenario is the expectation of enhanced top, bottom and tau production at the LHC, accompanied by large missing energy. Also, direct detection signals of dark matter may be more challenging to find than in conventional SUSY scenarios.
In the simplest SUSY extensions of the standard model, a 125 GeV Higgs motivates scalar masses in the tens of TeV range. However, scalar masses of this order are not large enough to immediately solve the SUSY flavor problem. At the same time, a WIMP solution to the dark matter problem motivates neutralino masses at or below a TeV. This suggests a micro-split spectrum with gaugino masses an order of magnitude below the scalar masses. We construct a simple framework that realizes the flavor safe micro-split spectrum favored by the Higgs mass and WIMP dark matter. We comment on the possibilities for discovery of this scenario at current dark matter experiments, the LHC, and future colliders.
We present a supersymmetric (SUSY) version of a two-field relaxion model that naturalizes supersymmetric models with high SUSY-breaking. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to ~ 10^9 GeV. This can explain the tuning in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem.
In this talk we give an overview about the status and recent developments in the field of automated NLO calculations and their combination with Monte Carlo tools.
We will discuss the underlying ideas that have led to the NLO revolution and describe how these methods have been applied to actual calculations.
Finally we also give an outlook about possible future developments and challenges in this field.
Package-X is a Mathematica package designed to analytically compute dimensionally regularized one-loop Feynman Integrals. In this talk I will showcase many new features in the upcoming update, Package-X 2.0. Among them are (1) the ability to handle four propagator factors, (2) test for power infrared divergences, (3) construct Taylor series expansions, and many many more.
For more information, see http://packagex.hepforge.org/version2public/version2public.html .
NLO Higgs (EW production) matched to parton shower
NLO Higgs gluon-fusion merged at NLO
first steps of uncertainty estimation
We study Higgs pair production with a subsequent decay to a pair of photons and a pair of bottom quarks at the LHC using the analysis tool MadMax. Based on the Neyman-Pearson Lemma, MadMax computes both the maximum significance for a signal extraction as well as its differential distribution. This allows us to better understand which phase space regions contribute to the extraction of the Higgs pair signal from backgrounds. We then use MadMax to estimate the sensitivity for the measurement of the Higgs self-coupling.
The use of NLO and multileg Monte Carlo generators by the ATLAS experiment in
the analysis of 13 TeV data is discussed. Procedures to validate these
generators by comparing results obtained using data collected at 7 TeV,
8 TeV and 13 TeV to the generator predictions are described. Techniques
used to evaluate systematic uncertainties on Monte Carlo modelling are
also discussed.
We present a classification of 4d rank 1 $\mathcal{N}=2$ Superconformal Field Theories (SCFTs), based on a geometrical analysis of the Coulomb Branches of these theories, i.e., their moduli space of vacua.
Supersymmetry and the residual $U(1)$ gauge symmetry on the Coulomb Branch allow us to constrain the geometries that can be consistently interpreted as low energy moduli space of a SCFT.
The same scale invariant geometry can correspond to multiple SCFTs, differing by the structure of their flavor symmetry, realized in the low energy description as different matter content.
Our analysis consists in starting with scale invariant Coulomb Branch geometries and classify the possible deformations of such geometries, thus determining the allowed set of rank-1 $\mathcal{N}=2$ SCFTs with their corresponding flavor algebras.