180 research outputs found

    Search for new physics in high-mass diphoton events from proton-proton collisions at √s = 13 TeV

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    Results are presented from a search for new physics in high-mass diphoton events from proton-proton collisions at sqrt(s) = 13 TeV. The data set was collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb−1 . Events with a diphoton invariant mass greater than 500 GeV are considered. Two diferent techniques are used to predict the standard model backgrounds: parametric fts to the smoothly-falling background and a frst-principles calculation of the standard model diphoton spectrum at next-to-next-to-leading order in perturbative quantum chromodynamics calculations. The frst technique is sensitive to resonant excesses while the second technique can identify broad diferences in the invariant mass shape. The data are used to constrain the production of heavy Higgs bosons, Randall-Sundrum gravitons, the large extra dimensions model of Arkani-Hamed, Dimopoulos, and Dvali (ADD), and the continuum clockwork mechanism. No statistically signifcant excess is observed. The present results are the strongest limits to date on ADD extra dimensions and RS gravitons with a coupling parameter greater than 0.1

    Search for high-mass resonances in final states with a lepton and missing transverse momentum at root s=13 TeV

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    A search for new high-mass resonances in proton-proton collisions having final states with an electron or muon and missing transverse momentum is presented. The analysis uses proton-proton collision data collected in 2016 with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 35.9 fb(-1). The transverse mass distribution of the charged lepton-neutrino system is used as the discriminating variable. No significant deviation from the standard model prediction is found. The best limit, from the combination of electron and muon channels, is 5.2TeV at 95% confidence level for the mass of a W' boson with the same couplings as those of the standard model Wboson. Exclusion limits of 2.9TeV are set on the inverse radius of the extra dimension in the framework of split universal extra dimensions. In addition, model-independent limits are set on the production cross section and coupling strength of W' bosons decaying into this final state. An interpretation is also made in the context of an R parity violating supersymmetric model with a slepton as a mediator and flavor violating decay.Peer reviewe

    Search for chargino-neutralino production in events with Higgs and W bosons using 137 fb−1 of proton-proton collisions at √s = 13 TeV

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    A search for electroweak production of supersymmetric (SUSY) particles in final states with one lepton, a Higgs boson decaying to a pair of bottom quarks, and large missing transverse momentum is presented. The search uses data from proton-proton collisions at a center-of-mass energy of 13 TeV collected using the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. The observed yields are consistent with backgrounds expected from the standard model. The results are interpreted in the context of a simplified SUSY model of chargino-neutralino production, with the chargino decaying to a W boson and the lightest SUSY particle (LSP) and the neutralino decaying to a Higgs boson and the LSP. Charginos and neutralinos with masses up to 820 GeV are excluded at 95% confidence level when the LSP mass is small, and LSPs with mass up to 350 GeV are excluded when the masses of the chargino and neutralino are approximately 700 GeV. [Figure not available: see fulltext.]. © 2021, The Author(s)

    Search for W´ bosons decaying to a top and a bottom quark at root s=13 TeV in the hadronic final state

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    A search is performed for W ' bosons decaying to a top and a bottom quark in the all-hadronic final state, in proton-proton collisions at a center-of-mass energy of 13TeV. The analyzed data were collected by the CMS experiment between 2016 and 2018 and correspond to an integrated luminosity of 137fb(-1). Deep neural network algorithms are used to identify the jet initiated by the bottom quark and the jet containing the decay products of the top quark when the W ' boson from the top quark decays hadronically. No excess above the estimated standard model background is observed. Upper limits on the production cross sections of W ' bosons decaying to a top and a bottom quark are set. Both left- and right-handed W ' bosons with masses below 3.4TeV are excluded at 95% confidence level, and the most stringent limits to date on W ' bosons decaying to a top and a bottom quark in the all-hadronic final state are obtained. (C) 2021 The Author(s). Published by Elsevier B.V.Peer reviewe

    Search for top squarks in final states with two top quarks and several light-flavor jets in proton-proton collisions at √s =13 TeV

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    Many new physics models, including versions of supersymmetry characterized by R-parity violation (RPV), compressed mass spectra, long decay chains, or additional hidden sectors, predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for new physics in events with two top quarks and additional jets are reported. The search is performed using events with at least seven jets and exactly one electron or muon. No requirement on missing transverse momentum is imposed. The study is based on a sample of proton-proton collisions at s=13TeV corresponding to 137 fb-1 of integrated luminosity collected with the CMS detector at the LHC in 2016-2018. The data are used to determine best fit values and upper limits on the cross section for pair production of top squarks in scenarios of RPV and stealth supersymmetry. Top squark masses up to 670 (870) GeV are excluded at 95% confidence level for the RPV (stealth) scenario, and the maximum observed local signal significance is 2.8 standard deviations for the RPV scenario with top squark mass of 400 GeV. © 2021 CERN

    Search for the lepton flavor violating decay tau -> 3 mu in proton-proton collisions at root s=13 TeV

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    Results are reported from a search for the lepton flavor violating decay tau -> 3 mu in proton-proton collisions at root s = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb(-1) recorded by the CMS experiment at the LHC in 2016. The search exploits tau leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction B(tau -> 3 mu) of 8.0 x 10(-8) at 90% confidence level is obtained, with an expected upper limit of 6.9 x 10(-8).Peer reviewe

    Search for Wγ resonances in proton-proton collisions at s=13 TeV using hadronic decays of Lorentz-boosted W bosons

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    A search for Wγ resonances in the mass range between 0.7 and 6.0 TeV is presented. The W boson is reconstructed via its hadronic decays, with the final-state products forming a single large-radius jet, owing to a high Lorentz boost of the W boson. The search is based on proton-proton collision data at s=13 TeV, corresponding to an integrated luminosity of 137 fb−1, collected with the CMS detector at the LHC in 2016–2018. The Wγ mass spectrum is parameterized with a smoothly falling background function and examined for the presence of resonance-like signals. No significant excess above the predicted background is observed. Model-specific upper limits at 95% confidence level on the product of the cross section and branching fraction to the Wγ channel are set. Limits for narrow resonances and for resonances with an intrinsic width equal to 5% of their mass, for spin-0 and spin-1 hypotheses, range between 0.17 fb at 6.0 TeV and 55 fb at 0.7 TeV. These are the most restrictive limits to date on the existence of such resonances over a large range of probed masses. In specific heavy scalar (vector) triplet benchmark models, narrow resonances with masses between 0.75 (1.15) and 1.40 (1.36) TeV are excluded for a range of model parameters. Model-independent limits on the product of the cross section, signal acceptance, and branching fraction to the Wγ channel are set for minimum Wγ mass thresholds between 1.5 and 8.0 TeV

    Measurement of the inclusive and differential t(t)over-bar gamma cross sections in the single-lepton channel and EFT interpretation at root s=13 TeV

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    Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at √s = 13 TeV

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    Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at s = 13 TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb−1. Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12±0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations. [Figure not available: see fulltext.] © 2021, The Author(s)
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