Conveners
WG3: Electroweak Physics and Beyond the Standard Model: Session 1
- Heidi Angelika Rzehak
- Heather Gray (UC Berkeley/LBNL)
- Adam Orion Martin (University of Notre Dame (US))
WG3: Electroweak Physics and Beyond the Standard Model: Session 2
- Heather Gray (UC Berkeley/LBNL)
- Adam Orion Martin (University of Notre Dame (US))
- Heidi Angelika Rzehak
WG3: Electroweak Physics and Beyond the Standard Model: Session 3
- Heidi Angelika Rzehak
- Heather Gray (UC Berkeley/LBNL)
- Adam Orion Martin (University of Notre Dame (US))
With the full Run 2 pp collision dataset collected at 13 TeV, very detailed measurements of Higgs boson properties and its interactions can be performed using its decays into bosons and fermions, shining light over the electroweak symmetry breaking mechanism. This talk presents the latest measurements of the Higgs boson couplings by the ATLAS experiment in various decay channels, including...
With the pp collision dataset collected at 13 TeV, detailed measurements of Higgs boson properties can be performed. The Higgs kinematics and CP properties can be measured with various production and decay modes and interpreted to constrain beyond-the-Standard-Model phenomena. This talk presents the measurements of Higgs boson differential and fiducial cross-sections as well as their...
One of the simplest extensions of the Standard Model (SM) Higgs sector is the Higgs singlet extension in which one adds a singlet to the particle content of the SM. Such models are being studied at the LHC. In the simplest realization of this model, in which the singlet is real, there are two Higgs bosons and only three new parameters, two mixing angles and the mass of the additional Higgs...
In the Standard Model, the ground state of the Higgs field is not found at zero but instead corresponds to one of the degenerate solutions minimising the Higgs potential. In turn, this spontaneous electroweak symmetry breaking provides a mechanism for the mass generation of nearly all fundamental particles. The Standard Model makes a definite prediction for the Higgs boson self-coupling and...
The discovery of the Higgs boson with the mass of 125 GeV completed the particle content predicted by the Standard Model. Even though this model is well established and consistent with many measurements, it is not capable to solely explain some observations. Many extensions of the Standard Model addressing such shortcomings introduce additional Higgs-like bosons which can be either neutral or...
The LHCb detector at the LHC offers unique coverage of forward rapidities. The detector also has a flexible trigger that enables low-mass states to be recorded with high efficiency, and a precision vertex detector that enables excellent separation of primary interactions from secondary decays. This allows LHCb to make significant (and world-leading) contributions in these regions of phase...
The presence of a non-baryonic Dark Matter (DM) component in the Universe is inferred from the observation of its gravitational interaction. If Dark Matter interacts weakly with the Standard Model (SM) it could be produced at the LHC. The ATLAS experiment has developed a broad search program for DM candidates, including resonance searches for the mediator which would couple DM to the SM,...
Various theories beyond the Standard Model predict new, long-lived particles with unique signatures which are difficult to reconstruct and for which estimating the background rates is also a challenge. Signatures from displaced and/or delayed decays anywhere from the inner detector to the muon spectrometer, as well as those of new particles with fractional or multiple values of the charge of...
We study the impact of the inclusion of a light baryonic boson B (which we henceforth refer to as a dark photon), primarily coupled to quarks, as a constituent of the proton; this is achieved by including a dark photon parton distribution function (PDF) in the standard PDF evolution equations. Depending on the proposed mass and coupling of the dark photon, the evolution of light quark and...
FASER$\nu$ is designed to directly detect collider neutrinos of all three flavors for the first time and provide new measurements of their cross-sections at energies higher than those detected from any previous artificial sources. In the pilot run data during LHC Run 2 in 2018, we observed the first neutrino interaction candidates at the LHC, opening a new avenue for studying neutrinos from...
The NA62 experiment at CERN took data in 2016-2018 with the main goal of measuring the K+ -> pi+ nu nubar decay.
A large sample of charged kaon decays into final states with multiple charged particles has been collected in 2016-2018 by the NA62 experiment at CERN. This sample provides sensitivities to lepton flavour/number violating decays of the charged kaon and of the neutral pion with...
The NA62 experiment at CERN took data in 2016--2018 with the main goal of measuring the K+ -> pi+ nu nubar decay. The high-intensity fixed-target setup and the detector performance make the NA62 experiment particularly suited to investigate the Standard Model structure and its possible extensions with precision measurements of charged kaon decays.
Results from studies of the radiative kaon...
The decay K+→π+ νν ̅, with a very precisely predicted branching ratio of less than 10-10, is among the best processes to reveal indirect effects of new physics.
The NA62 experiment reports the branching ratio measurement BR(K+→π+νν¯) = (10.6+4.0−3.4|stat ± 0.9syst) × 10−11 at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data...
Preliminary results of the K± → µ ± π0π0ν (Kmu400) decay first observation and analysis based on the NA48/2 data collected in 2003-2004 are presented. The branching ratio measurement is done on the basis of 2437 selected candidates with about 20% background. In the restricted region of squared dilepton mass above 0.03 GeV^2/c^4, the branching ratio is Br(Kmu400, M2(2l)>0.03 GeV2/c4) = (0.65 ±...
Vector boson scattering is a key production process to probe the electroweak symmetry breaking of the standard model, since it involves both self-couplings of vector bosons and coupling with the Higgs boson. If the Higgs mechanism is not the sole source of electroweak symmetry breaking, the scattering amplitude deviates from the standard model prediction at high scattering energy. Moreover,...
This talk reviews recent measurements of multiboson production using CMS data. Inclusive and differential cross sections are measured using several kinematic observables.
Measurements of multiboson production at the LHC probe the electroweak gauge structure of the Standard Model for contributions from anomalous couplings. In this talk we present recent ATLAS results on the first observation of three W boson production at the LHC (WWW). If available, we also present the differential cross-section measurement of the Z boson produced in association with two...
The scattering of electroweak bosons tests the gauge structure of the Standard Model and is sensitive to anomalous weak boson self interactions. In this talk, we present recent results on weak-boson scattering from the ATLAS experiment using proton-proton collisions at sqrt(s)=13 TeV. We present the first observation of Z+jets production, in two final states where the Z boson decays...
We present a Monte Carlo generator for off-shell top-quark pair production and decay in the semileptonic channel. The generator takes form of an extension to a generator which implements $t\bar{t}$ production in the dileptonic channel in terms of the exact matrix elements for $pp\to \ell^+\nu_{\ell}\, l^-\bar{\nu}_{l}b\bar{b}$ at order $\alpha^4 \alpha_s^2$ plus full NLO QCD corrections. The...
Ultraperipheral lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$ TeV produce very large photon fluxes that provide the conditions to study photon-photon fusion processes in phase space regions inaccessible with proton-proton data. Measurements of light-by-light ( LbL) scattering and e+e- (Breit-Wheeler) production in ultraperipheral PbPb collisions with data collected during the 2015...
Ultraperipheral lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$ TeV produce very large photon fluxes that fundamental quantum-mechanical processes can be observed. In this presentation, the first observation of the $\tau$ lepton production in ultraperipheral PbPb collision data collected by CMS at LHC is reported. This measurement paves the way for the determination of the anomalous...
Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons, leading to multiple photon-induced processes. This talk presents a series of measurements of such processes performed by the ATLAS Collaboration. New measurements of exclusive dilepton production (electron, muon, and tau pairs) are discussed. These processes provide strong constraints on the nuclear...
Building upon the most recent CT18 global fit, we present a new set of parton distribution functions including the photon content of the proton based on an application of the LUX formalism. In this work, we explore two principal variations of the LUX ansatz. In one approach, which we designate "CT18lux," the photon PDF is calculated directly using the LUX formula for all scales, $\mu$. In an...
We present the MSHT20qed set of parton distribution functions (PDFs). These are obtained from the MSHT20 global analysis via a refit including QED corrections to the DGLAP evolution at ${\cal O}(\alpha),{\cal O}(\alpha\alpha_S)$ and ${\cal O}(\alpha^2)$, and containing the photon PDF of the proton. As in the previous MMHT15qed study we use an input distribution for the photon that is derived...
In this talk we will present a new calculation of $W^+ W^-$ production in the semi--exclusive channel, that is either with intact outgoing protons or rapidity gaps present in the final state, and with no colour flow between the colliding protons. This study provides the first complete prediction of the $W^+ W^-$ semi--exclusive cross section, as well as the breakdown between elastic and...
This talk reviews the most recent results in the study of standard model physics data analysis with the data collected by the CMS Collaboration.
The LHCb experiment covers the forward region of proton-proton collisions, and it can improve the current electroweak landscape by studying the production of electroweak bosons in this phase space complementary to ATLAS and CMS. In this talk, an overview of the wide LHCb electroweak measurement program will be presented. This includes the recent measurement of the W boson mass.
Incompleteness in current knowledge of neutrino interactions with nuclear matter imposes a primary limitation in searches for leptonic CP violation carried out at long-baseline neutrino experiments like DUNE. In this talk, we summarize a recent computation that elevates the theoretical accuracy to next-to-next-to-leading order in QCD for charged-current DIS processes relevant for ongoing and...
We provide state-of-the art SCETlib predictions for the $W$ and $Z/\gamma^*$ transverse-momentum ($q_T$) distributions at the LHC at complete three-loop order in resummed perturbation theory (N$^3$LL$'$) and matched to available fixed order. We compare our predictions to high-precision measurements by the ATLAS and CMS experiments. We pay particular attention to the estimation of theory...
The Precision Proton Spectrometer (PPS) is a new subdetector of CMS introduced for the LHC Run 2, which provides a powerful tool for advancement of BSM searches. The talk will present the new results on exclusive diphoton, ttbar, Z+X, and diboson production explored with with PPS, illustrating the unique sensitivity which can be achieved using proton tagging.
Many theories beyond the Standard Model (BSM) have been proposed to address several of the Standard Model shortcomings, such as the origin of dark matter and neutrino masses, the fine-tuning of the Higgs Boson mass, or the observed pattern of masses and mixing angles in the quark and lepton sectors. Many of these BSM extensions predict new particles or interactions directly accessible at the...
Thermal dark matter candidates are usually associated with the Weakly-interacting massive particles (WIMPS). However, vanilla WIMP scenarios suffer from severe experimental constraints. I would therefore like to discuss two alternatives to the standard picture: Inelastic Dark Matter and Dark Sectors with Bound States. In both cases, a dark matter candidate is in thermal contact with the...
Decays of B mesons that proceed through electroweak and radiative penguin amplitudes currently attract significant attention due to a number of observed discrepancies between the standard model predictions and the experimental results.
Belle II is expected to perform measurements on channels closely related to those exhibiting anomalies and that are uniquely available to Belle II. These...
The search for lepton flavour violation is regarded as one of the main roads in the quest for new physics beyond the Standard Model. At PSI, Switzerland, the MEG II experiment will search for the $\mu \rightarrow e \gamma$ decay with the capability of setting an upper limit down to $6 \times 10^{-14}$, one order of magnitude below the result of the first-phase MEG experiment. The MEG II...
We introduce an effort to catalog the gauge-invariant interactions of Standard Model (SM) particles and new fields in a variety of representations of the SM color gauge group SU(3)c. In this first installment, we direct this effort toward fields in the six-dimensional (sextet, 6) representation. We consider effective operators of mass dimension up to seven (comprehensively up to dimension...
Significant deviations from SM predictions have been observed in $ b \to s \mu^+ \mu^-$ decays and in the muon (g-2). Scalar leptoquark extensions of the SM are known to be able to address these anomalies, but generically give rise to lepton flavor violation or even proton decay. As a possible resolution, we introduce a lepton-flavored U(1) gauge symmetry to preserve the accidental symmetries...
One of the most interesting yet-to-be answered questions in Particle Physics is the nature of the Higgs Yukawa couplings and their universality. Key information in our understanding of this question arises from studying the coupling of the Higgs boson to second generation quarks. Some puzzles in the flavor sector and potential additional sources of CP violation could also have their origins in...
We present a parton-level study of electro-weak production of vector-boson pairs at the Large Hadron Collider, establishing the sensitivity to a set of dimension-six operators in the Standard Model Effective Field Theory (SMEFT). Different final states are statistically combined, and we discuss how the orthogonality and interdependence of different analyses must be considered to obtain the...
Global interpretations of particle physics data in the context of the Standard Model Effective Field Theory (SMEFT) rely on the combination of a wide range of physical observables from many different processes. We present ongoing work towards the integration of unbinned measurements into such global SMEFT interpretations by means of machine learning tools. We use a deep-learning...
The talk will be about applications of on-shell techniques to the Standard Model Effective Field Theory (SMEFT). I will present a systematic classification of marginal operators in generic effective field theories and the computation of their anomalous dimensions using only on-shell data. Finally, I will show explicit results in the context of the SMEFT.
In the Standard Model, CP violation in the Electroweak sector is parametrized by the Jarlskog Invariant. This is the order parameter of CP-violation, in the sense that it vanishes iff CP is conserved. When higher dimensional operators are allowed, and the Standard Model Effective Field Theory is constructed, numerous new sources for CP violation can appear. However, the description of CP...
Electroweak interactions assign a central role to the gauge group $SU(2)_L \times U(1)_Y$ , which is either realized linearly (SMEFT) or nonlinearly (e.g., HEFT) in the effective theory obtained when new physics above the electroweak scale is integrated out. Although the discovery of the Higgs boson has made SMEFT the default assumption, nonlinear realization remains possible.
I will...
We explore the interplay between the HEFT and SMEFT theories. Whereas the SMEFT has become the standard in the field of LHC phenomenology, the HEFT provides a more flexible description of the electroweak sector. In particular, we discuss various aspects of (multi-) Higgs production from longitudinal electroweak gauge bosons $W_LW_L\to n\times h$ in the TeV region, and compare predictions from...
Recent results from the proton-proton collision data taken by the ATLAS experiment on exotic resonances will be presented. A study of J/psi p resonances in the Lambda_b -> J/psi p K decays with large m(pK) invariant masses will be reported. Studies of Z_c states in B-meson decays with the Run 2 data at 13 TeV will also be discussed. Searches for exotic resonances in 4 muon final states will be...
High $p_T$ direct photons produced in initial hard scattering are not affected by the colored medium formed in heavy ion collisions. This has been observed in large-on-large ion collisions, where, in contrast, jets and final state hadrons show energy loss, measured via the nuclear modification factor that compares the observed yields to the expected yield from p+p scaled by the number of...
We present a phenomenological study of the single top (anti-)quark production with leptonic decays at the Large Hadron electron Collider (LHeC) at the next-to-leading-order (NLO) in QCD. We focus on various differential distributions in a fiducial region. The NLO corrections can reduce the fiducial cross section by 14%. We find the NLO predictions exhibit strong stability under scale...
The search for physics beyond the Standard Model (BSM) is one of the main goals of the LHC. Compared to standard proton-proton collision studies, heavy-ion collisions provide unique and complementary means to search for new phenomena. In particular, ultra-peripheral collisions (UPCs) of heavy ions offer a natural environment for the studies of photon-mediated processes, such as light-by-light...
Tests of Lorentz invariance continue to expand and challenge our understanding of spacetime symmetries in and beyond the Standard Model and General Relativity. Using a model-independent framework based on effective field theory, generic deviations from exact Lorentz invariance, CPT invariance, and other fundamental symmetries can be studied in a wide class of physical systems covering a broad...
Background modelling is one of the main challenges of particle physics analyses at hadron colliders. Commonly employed strategies are the use of simulations based on Monte Carlo event generators or the use of parametric methods. However, sufficiently accurate simulations are not always available or may be computationally costly to produce in high statistics, leading to uncertainties that can...
The feasibility of observing true tauonium, the ground bound-state of two tau leptons $\mathcal{T}_0\equiv(\tau^+\tau^-)$, via photon-photon collisions at current and future colliders is studied. The production cross sections of the process $\gamma\gamma\to\mathcal{T}_0\to\gamma\gamma$ ---as well as those of all relevant backgrounds: spin-0 and 2 charmonium resonances decaying to diphotons,...
To resolve the long-standing discrepancy between the precision measurement of bottom quark forward-backward asymmetry at LEP/SLC and the Standard Model prediction, we propose a novel method to probe the $Zb\bar{b}$ coupling by measuring the (average jet charge weighted) single-spin asymmetry of the polarized lepton cross section in neutral current DIS processes with a b-tagged jet at HERA and...
To address the incompleteness of the Standard Model (SM), many models, e.g compositeness, extra dimensions, have predicted the existence of new resonances at the LHC in the final state of a photon and a jet. If such a resonance exists, the signal would appear as a bump on top of the smooth invariant mass distribution of the SM background processes. A search is presented for new resonances...
Many new physics models predict the existence of Higgs-like particles decaying into two bosons (W, Z, photon, or Higgs bosons) making these important signatures in the search for new physics. Searches for V??, VV, and VH resonances have been performed in various final states. In some of these searches, jet substructure techniques are used to disentangle the hadronic decay products in highly...
Ultra-peripheral collisions of heavy ions (UPCs) serve as a valuable source of experimental data for studies of photon-photon interactions. One of the latest examples is the evidence of light-by-light scattering process (LbyL) first established by the CMS and ATLAS collablorations at the LHC. UPCs were also proposed as a tool for searches of effects of physics beyond the Standard Model (BSM),...
