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  1. Search for Baryon Number Violation in Top Quark Production and Decay Using Proton-Proton Collisions at s = 13 TeV

    A semore » arch is presented for baryon number violating interactions in top quark production and decay. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC with an integrated luminosity of 138 fb 1 . Candidate events are selected by requiring two oppositely charged leptons (electrons or muons) and exactly one jet identified as originating from a bottom quark. Multivariate discriminants are used to separate the signal from the background. No significant deviation from the standard model prediction is observed. Upper limits are placed on the strength of baryon number violating couplings. For the first time the production of single top quarks via baryon number violating interactions is studied. This allows the search to set the most stringent constraints to date on the branching fraction of the top quark decay to a lepton, an up-type quark ( u or c ), and a down-type quark ( d , s , or b ). The results improve the previous bounds by 3 to 6 orders of magnitude based on the fermion flavor combination of the baryon number violating interactions. © 2024 CERN, for the CMS Collaboration 2024 CERN« less
  2. Observation of the J / ψ μ + μ μ + μ decay in proton-proton collisions at s = 13 TeV

    Tmore » he J / ψ μ + μ μ + μ decay has been observed with a statistical significance in excess of five standard deviations. he analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 eV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6 fb 1 . Normalizing to the J / ψ μ + μ decay mode leads to a branching fraction of [ 10.1 2.7 + 3.3 ( stat ) ± 0.4 ( syst ) ] × 10 7 , a value that is consistent with the standard model prediction. © 2024 CERN, for the CMS Collaboration 2024 CERN« less
  3. Combined search for electroweak production of winos, binos, higgsinos, and sleptons in proton-proton collisions at s = 13 TeV

    A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision data atmore » $$\sqrt{s}$$ =13 TeV recorded with the CMS detector at the LHC in 2016–2018. The analyzed data correspond to an integrated luminosity of up to 137 fb-1. The results are interpreted in terms of simplified models of supersymmetry. Two new interpretations are added with this combination: a model spectrum with the bino as the lightest supersymmetric particle together with mass-degenerate Higgsinos decaying to the bino and a standard model boson, and the compressed-spectrum region of a previously studied model of slepton pair production. Improved analysis techniques are employed to optimize sensitivity for the compressed spectra in the wino and slepton pair production models. The results are consistent with expectations from the standard model. The combination provides a more comprehensive coverage of the model parameter space than the individual searches, extending the exclusion by up to 125 GeV, and also targets some of the intermediate gaps in the mass coverage.« less
  4. Search for long-lived particles using displaced vertices and missing transverse momentum in proton-proton collisions at s = 13 TeV

    A search for the production of long-lived particles in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC is presented. The search is based on data collected by the CMS experiment in 2016–2018, corresponding to a total integrated luminosity of 137 fb-1. This search is designed to be sensitive to long-lived particles with mean proper decay lengths between 0.1 and 1000 mm, whose decay products produce a final state with at least one displaced vertex and missing transverse momentum. A machine learning algorithm, which improves the background rejection power by more than an order of magnitude,more » is applied to improve the sensitivity. The observation is consistent with the standard model background prediction, and the results are used to constrain split supersymmetry (SUSY) and gauge mediated SUSY breaking models with different gluino mean proper decay lengths and masses. This search is the first CMS search that shows sensitivity to hadronically decaying long-lived particles from signals with mass differences between the gluino and neutralino below 100 GeV. It sets the most stringent limits to date for split-SUSY models and gauge-mediated SUSY breaking models with gluino proper decay length less than 6 mm.« less
  5. Search for pair production of scalar and vector leptoquarks decaying to muons and bottom quarks in proton-proton collisions at s = 13 TeV

    A search for pair production of scalar and vector leptoquarks (LQs) each decaying to a muon and a bottom quark is performed using proton-proton collision data collected atmore » $$\sqrt{s}$$ = 13 TeV with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 138 fb-1. No excess above standard model expectation is observed. Scalar (vector) LQs with masses less than 1810 (2120) GeV are excluded at 95% confidence level, assuming a 100% branching fraction of the LQ decaying to a muon and a bottom quark. These limits represent the most stringent to date.« less
  6. Search for a new resonance decaying into two spin-0 bosons in a final state with two photons and two bottom quarks in proton-proton collisions at $$\sqrt{s}$$ = 13 TeV

    A search for a new boson X is presented using CERN LHC proton-proton collision data collected by the CMS experiment atmore » $$\sqrt{s}$$ = 13 TeV in 2016–2018, and corresponding to an integrated luminosity of 138 fb-1. The resonance X decays into either a pair of Higgs bosons HH of mass 125 GeV or an H and a new spin-0 boson Y. One H subsequently decays to a pair of photons, and the second H or Y, to a pair of bottom quarks. The explored mass ranges of X are 260–1000 GeV and 300–1000 GeV, for decays to HH and to HY, respectively, with the Y mass range being 90–800 GeV. For a spin-0 X hypothesis, the 95% confidence level upper limit on the product of its production cross section and decay branching fraction is observed to be within 0.90–0.04 fb, depending on the masses of X and Y. The largest deviation from the background-only hypothesis with a local (global) significance of 3.8 (below 2.8) standard deviations is observed for X and Y masses of 650 and 90 GeV, respectively. The limits are interpreted using several models of new physics.« less
  7. Search for a third-generation leptoquark coupled to a τ lepton and a b quark through single, pair, and nonresonant production in proton-proton collisions at $$\sqrt{s}$$ = 13 TeV

    A search is presented for a third-generation leptoquark (LQ) coupled exclusively to a τ lepton and a b quark. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 138 fb-1. Events with τ leptons and a varying number of jets originating from b quarks are considered, targeting the single and pair production of LQs, as well as nonresonant t-channel LQ exchange. An excess is observed in the data with respect to the background expectation in the combined analysis of all search regions. Formore » a benchmark LQ mass of 2 TeV and an LQ-b-τ coupling strength of 2.5, the excess reaches a local significance of up to 2.8 standard deviations. Upper limits at the 95% confidence level are placed on the LQ production cross section in the LQ mass range 0.5–2.3 TeV, and up to 3 TeV for t-channel LQ exchange. Leptoquarks are excluded below masses of 1.22–1.88 TeV for different LQ models and varying coupling strengths up to 2.5. The study of nonresonant ττ production through t-channel LQ exchange allows lower limits on the LQ mass of up to 2.3 TeV to be obtained.« less
  8. Measurement of simplified template cross sections of the Higgs boson produced in association with W or Z bosons in the H b b ¯ decay channel in proton-proton collisions at s = 13 TeV

    Differenmore » tial cross sections are measured for the standard model Higgs boson produced in association with vector bosons ( W , Z ) and decaying to a pair of b quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the W and Z bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved b -tagged jets, or from single large-radius jets containing the particles arising from two b quarks. Proton-proton collision data at s =13 TeV , collected by the CMS experiment in 2016–2018 and corresponding to a total integrated luminosity of 138 fb - 1 , are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be μ=1.1 5 - 0.20 + 0.22 . This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.« less
  9. Development of the CMS detector for the CERN LHC Run 3

    Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and themore » beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger.« less
  10. Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the μμ $$\text{b}$$ $$\text{b}$$ and $$\tau\tau$$ $$\text{b}$$ $$\text{b}$$ final states

    A search for exotic decays of the Higgs boson (H) with a mass of 125 GeV to a pair of light pseudoscalars a1 is performed in final states where one pseudoscalar decays to two b quarks and the other to a pair of muons or τ leptons. A data sample of proton–proton collisions atmore » $$\sqrt{s} = 13 TeV corresponding to an integrated luminosity of 138 fb-1 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level (CL) on the Higgs boson branching fraction to μμ b b and to ττ b b via a pair of a1s. The limits depend on the pseudoscalar mass ma1 and are observed to be in the range (0.17–3.3) x 10-4 and (1.7–7.7) x 10-2 in the μμ b b and ττ b b final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction $$\mathcal{B}$(H→a1a1→ ℓℓ b b) at 95% CL, with ℓ being a muon or a τ lepton. For different types of 2HDM+S, upper bounds on the branching fraction are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, $$\mathcal{B}$$(H→a1a1) values above 0.23 are excluded at 95% CL for ma1 values between 15 and 60 GeV.« less
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