Observation of γγ → ττ in proton-proton collisions and limits on the anomalous electromagnetic moments of the τ lepton

The production of a pair of τ leptons via photon–photon fusion, γγ → ττ, is observed for the f irst time in proton–proton collisions, with a significance of 5.3 standard deviations. This observation is based on a data set recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb−1. Events with a pair of τ leptons produced via photon–photon fusion are selected by requiring them to be back-to-back in the azimuthal direction and to have a minimum number of charged hadrons associated with their production vertex. The τ leptons are reconstructed in their leptonic and hadronic decay modes. The measured fiducial cross section of γγ → ττ is σfid obs = 12.4+3.8 −3.1 fb. Constraints are set on the contributions to the anomalous magnetic moment (aτ) and electric dipole moments (dτ) of the τ lepton originating from potential effects of new physics on the γττ vertex: aτ = 0.0009+0.0032 −0.0031 and |dτ| < 2.9×10−17ecm (95% confidence level), consistent with the standard model

Probing EFT models using top quark production in multilepton final states

Using data consisting of top quarks produced with additional final leptons collected by the CMS detector at a center-of-mass energy of $\sqrt{s}=$13 TeV from 2016 to 2018 (138 fb$^{-1}$), a search for beyond standard model (BSM) physics is presented. The BSM physics is probed in the context of Effective Field Theory (EFT) by parameterizing potential new physics effects in terms of 26 dimension-six EFT operators. The data are categorized based on lepton multiplicity, total lepton charge, jet multiplicities, and b-tagged jet multiplicities. To gain further sensitivity to potential new physics (NP) effects, events in each jet category are binned using kinematic differential distributions. A simultaneous fit to data is performed to put constraints on the 26 operators. The results are consistent with the standard model prediction

[YSF] Probing EFT models using top quark production in multilepton final states

Using data consisting of top quarks produced with additional final leptons collected by the CMS detector at a center-of-mass energy of $\sqrt{s}$ =13 TeV from 2016 to 2018 (138 fb$^{-1}$), a search for beyond standard model (BSM) physics is presented. The BSM physics is probed in the context of Effective Field Theory (EFT) by parameterizing potential new physics effects in terms of 26 dimension-six EFT operators. The data are categorized based on lepton multiplicity, total lepton charge, jet multiplicities, and b tagged jet multiplicities. To gain further sensitivity to potential new physics (NP) effects, events in each jet category are binned using17 kinematic differential distributions. A simultaneous fit to data is performed to put constraints on the 26 operators. The results are consistent with the standard model prediction

EFT Workshop at Notre Dame

International audienceThe LPC EFT workshop was held April 25-26, 2024 at the University of Notre Dame. The workshop was organized into five thematic sessions: "how far beyond linear" discusses issues of truncation and validity in interpretation of results with an eye towards practicality; "reconstruction-level results" visits the question of how best to design analyses directly targeting inference of EFT parameters; "logistics of combining likelihoods" addresses the challenges of bringing a diverse array of measurements into a cohesive whole; "unfolded results" tackles the question of designing fiducial measurements for later use in EFT interpretations, and the benefits and limitations of unfolding; and "building a sample library" addresses how best to generate simulation samples for use in data analysis. This document serves as a summary of presentations, subsequent discussions, and actionable items identified over the course of the workshop

EFT Workshop at Notre Dame

International audienceThe LPC EFT workshop was held April 25-26, 2024 at the University of Notre Dame. The workshop was organized into five thematic sessions: "how far beyond linear" discusses issues of truncation and validity in interpretation of results with an eye towards practicality; "reconstruction-level results" visits the question of how best to design analyses directly targeting inference of EFT parameters; "logistics of combining likelihoods" addresses the challenges of bringing a diverse array of measurements into a cohesive whole; "unfolded results" tackles the question of designing fiducial measurements for later use in EFT interpretations, and the benefits and limitations of unfolding; and "building a sample library" addresses how best to generate simulation samples for use in data analysis. This document serves as a summary of presentations, subsequent discussions, and actionable items identified over the course of the workshop

EFT Workshop at Notre Dame

The LPC EFT workshop was held April 25-26, 2024 at the University of Notre Dame. The workshop was organized into five thematic sessions: "how far beyond linear" discusses issues of truncation and validity in interpretation of results with an eye towards practicality; "reconstruction-level results" visits the question of how best to design analyses directly targeting inference of EFT parameters; "logistics of combining likelihoods" addresses the challenges of bringing a diverse array of measurements into a cohesive whole; "unfolded results" tackles the question of designing fiducial measurements for later use in EFT interpretations, and the benefits and limitations of unfolding; and "building a sample library" addresses how best to generate simulation samples for use in data analysis. This document serves as a summary of presentations, subsequent discussions, and actionable items identified over the course of the workshop

New Structures in the <math display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> Mass Spectrum in Proton-Proton Collisions at <math display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>

A search is reported for near-threshold structures in the J/ψJ/ψ invariant mass spectrum produced in proton-proton collisions at s=13  TeV from data collected by the CMS experiment, corresponding to an integrated luminosity of 135  fb-1. Three structures are found, and a model with quantum interference among these structures provides a good description of the data. A new structure is observed with a local significance above 5 standard deviations at a mass of 6638-38+43(stat)-31+16(syst)  MeV. Another structure with even higher significance is found at a mass of 6847-28+44(stat)-20+48(syst)  MeV, which is consistent with the X(6900) resonance reported by the LHCb experiment and confirmed by the ATLAS experiment. Evidence for another new structure, with a local significance of 4.7 standard deviations, is found at a mass of 7134-25+48(stat)-15+41(syst)  MeV. Results are also reported for a model without interference, which does not fit the data as well and shows mass shifts up to 150 MeV relative to the model with interference

Search for direct production of GeV-scale resonances decaying to a pair of muons in proton-proton collisions at s \sqrt{s} = 13 TeV

A search for direct production of low-mass dimuon resonances is performed using $\sqrt{s}$ = 13 TeV proton-proton collision data collected by the CMS experiment during the 2017–2018 operation of the CERN LHC with an integrated luminosity of 96.6 fb$^{−1}$. The search exploits a dedicated high-rate trigger stream that records events with two muons with transverse momenta as low as 3 GeV but does not include the full event information. The search is performed by looking for narrow peaks in the dimuon mass spectrum in the ranges of 1.1–2.6 GeV and 4.2–7.9 GeV. No significant excess of events above the expectation from the standard model background is observed. Model-independent limits on production rates of dimuon resonances within the experimental fiducial acceptance are set. Competitive or world's best limits are set at 90% confidence level for a minimal dark photon model and for a scenario with two Higgs doublets and an extra complex scalar singlet (2HDM+S). Values of the squared kinetic mixing coefficient ε$^{2}$ in the dark photon model above 10$^{−6}$ are excluded over most of the mass range of the search. In the 2HDM+S, values of the mixing angle sin(θ$_{H}$) above 0.08 are excluded over most of the mass range of the search with a fixed ratio of the Higgs doublets vacuum expectation tan β = 0.5.[graphic not available: see fulltext

Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at <math display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>

The results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (pTmiss), are reported. The study is based on a sample of proton-proton collisions at s=13  TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138  fb-1. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low pTmiss regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level