75 Search Results

We present a search for the pair production of Higgsinos in final states with large missing transverse momentum and either two reconstructed muons or a reconstructed lepton (muon or electron) and an isolated track. The analyzed data correspond to proton-proton collisions with an integrated luminosity of $137{\mathrm{fb}}^{-1}$ , collected by the CMS experiment at $\sqrt{s}=13\mathrm{TeV}$ in 2016, 2017, and 2018. The signal scenario assumes four nearly mass degenerate Higgsino mass eigenstates: two neutralino states ${\tilde{\chi }}_2^{more »}$ 0 and ${\tilde{\chi }}_1^0$ with a small mass difference in the range 1–10 GeV and two chargino states ${\tilde{\chi }}_1^{\pm }$ with an intermediate mass. The analysis focuses on the decay of the heavier neutralino into the lighter one and a virtual $Z$ boson, which decays into two same-flavor leptons. The leptons have small transverse momentum and/or a small opening angle between the identified muons. An isolated track is used to recover events in which only one of the two leptons is identified. Multivariate discriminants are used to enhance the sensitivity by efficiently rejecting backgrounds from SM processes or misreconstructed tracks and/or leptons. The search explores a unique phase space and probes a previously unexplored region of the signal model parameter space. Mass differences between the two neutralinos are probed down to 1.5 GeV, assuming a Higgsino mass of 100 GeV. The maximum excluded Higgsino mass is 115 GeV.« less

This Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb^-1. Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit ismore » 3.7 (6.1) times the standard model prediction« less

The first search for a heavy neutral spin-1 gauge boson (𝑍′) with nonuniversal fermion couplings produced via vector boson fusion processes and decaying to tau leptons or 𝑊 bosons is presented. The analysis is performed using LHC data at $$\sqrt{𝑠}$$ = 13 TeV, collected from 2016 to 2018 with the CMS experiment and corresponding to an integrated luminosity of 138 fb⁻¹. The data are consistent with the standard model predictions. Upper limits are set on the product of the cross section for production of the 𝑍′ boson and its branching fraction to 𝜏⁢𝜏 or 𝑊⁢𝑊. The presence of a 𝑍′more » boson decaying to 𝜏⁺⁢𝜏⁻ (𝑊⁺⁢𝑊⁻) is excluded for masses up to 2.45(1.60) TeV, depending on the 𝑍′ boson coupling to standard model weak bosons, and assuming a 𝑍′→𝜏⁺⁢𝜏⁻ (𝑊⁺⁢𝑊⁻) branching fraction of 50%.« less

A measurement of the Higgs boson mass and width via its decay to two 𝑍 bosons is presented. Proton-proton collision data collected by the CMS experiment, corresponding to an integrated luminosity of 138  fb⁻¹ at a center-of-mass energy of 13 TeV, is used. The invariant mass distribution of four leptons in the on-shell Higgs boson decay is used to measure its mass and constrain its width. This yields the most precise single measurement of the Higgs boson mass to date, 125.04 ± 0.12  GeV, and an upper limit on the width Γ_𝐻 < 330 MeV at 95% confidence level. A combination ofmore » the on- and off-shell Higgs boson production decaying to four leptons is used to determine the Higgs boson width, assuming that no new virtual particles affect the production, a premise that is tested by adding new heavy particles in the gluon fusion loop model. This result is combined with a previous CMS analysis of the off-shell Higgs boson production with decay to two leptons and two neutrinos, giving a measured Higgs boson width of 3.0$$^{+2.0}_{−1.5}$$ MeV, in agreement with the standard model prediction of 4.1 MeV. The strength of the off-shell Higgs boson production is also reported. The scenario of no off-shell Higgs boson production is excluded at a confidence level corresponding to 3.8 standard deviations.« less

The forward-backward asymmetry in Drell-Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at $$\sqrt{s}$$ = 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$$^{-1}$$. The measurement uses both dimuon and dielectron events, and is performed as a function of the dilepton mass and rapidity. The unfolded angular coefficient $$A_4$$ is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain $$\sin^{2}\theta^\ell_\text{eff}$$ = 0.23152 $$\pm$$ 0.00031, where the uncertainty includes the experimental and theoretical contributions. The measuredmore » value agrees with the standard model fit result to global experimental data. This is the most precise $$\sin^{2}\theta^\ell_\text{eff}$$ measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD.« less

Measurements of fiducial and total inclusive cross sections for W and Z boson production are presented in proton-proton collisions at $$ \sqrt{s} $$ = 5.02 and 13 TeV. Electron and muon decay modes (ℓ = e or μ) are studied in the data collected with the CMS detector in 2017, in dedicated runs with reduced instantaneous luminosity. The data sets correspond to integrated luminosities of 298 ± 6 pb$$^{−1}$$ at 5.02 TeV and 206 ± 5 pb$$^{−1}$$ at 13 TeV. Measured values of the products of the total inclusive cross sections and the branching fractions at 5.02 TeV are σ(ppmore » → W + X)$$ \mathcal{B} $$(W → ℓν) = 7300 ± 10 (stat) ± 60 (syst) ± 140 (lumi) pb, and σ(pp → Z+X)$$ \mathcal{B} $$(Z → ℓ$$^{+}$$ℓ$$^{−}$$) = 669 ± 2 (stat) ± 6 (syst) ± 13 (lumi) pb for the dilepton invariant mass in the range of 60–120 GeV. The corresponding results at 13 TeV are 20480 ± 10 (stat) ± 170 (syst) ± 470 (lumi) pb and 1952 ± 4 (stat) ± 18 (syst) ± 45 (lumi) pb. The measured values agree with cross section calculations at next-to-next-to-leading-order in perturbative quantum chromodynamics. Fiducial and total inclusive cross sections, ratios of cross sections of W$$^{+}$$ and W$$^{−}$$ production as well as inclusive W and Z boson production, and ratios of these measurements at 5.02 and 13 TeV are reported.« less

A measurement of the top quark pair ($$ \textrm{t}\overline{\textrm{t}} $$) production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default configuration, and correspond to an integrated luminosity of 302 pb$$^{−1}$$. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identified as originating from a b quark (b tagged). Events are classified based on the number of all reconstructed jets and ofmore » b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is $$ 62.5\pm 1.6{\left(\textrm{stat}\right)}_{-2.5}^{+2.6}\left(\textrm{syst}\right)\pm 1.2\left(\textrm{lumi}\right) $$ pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3 ± 1.5 (stat) ± 2.4 (syst) ± 1.2 (lumi) pb, to be compared with the standard model prediction of $$ {69.5}_{-3.7}^{+3.5} $$ pb at next-to-next-to-leading order in perturbative quantum chromodynamics.« less

A search for heavy, long-lived, charged particles with large ionization energy loss within the silicon tracker of the CMS experiment is presented. A data set of proton-proton collisions at a center of mass energy at $$\sqrt{s}$$ = 13 TeV, collected in 2017 and 2018 at the CERN LHC, corresponding to an integrated luminosity of 101 fb⁻¹, is used in this analysis. Two different approaches for the search are taken. A new method exploits the independence of the silicon pixel and strips measurements, while the second method improves on previous techniques using ionization to determine a mass selection. No significant excessmore » of events above the background expectation is observed. The results are interpreted in the context of the pair production of supersymmetric particles, namely gluinos, top squarks, and tau sleptons, and of the Drell-Yan pair production of fourth generation (τ′) leptons with an electric charge equal to or twice the absolute value of the electron charge (e). An interpretation of a Z’ boson decaying to two τ′ leptons with an electric charge equal to 2e is presented for the first time. The 95% confidence upper limits on the production cross section are extracted for each of these hypothetical particles.« less

Abstract A search for heavy, long-lived, charged particles with large ionization energy loss within the silicon tracker of the CMS experiment is presented. A data set of proton-proton collisions at a center of mass energy at $$$$ \sqrt{s} $$$$ s = 13 TeV, collected in 2017 and 2018 at the CERN LHC, corresponding to an integrated luminosity of 101 fb −1, is used in this analysis. Two different approaches for the search are taken. A new method exploits the independence of the silicon pixel and strips measurements, while the second method improves on previousmore » techniques using ionization to determine a mass selection. No significant excess of events above the background expectation is observed. The results are interpreted in the context of the pair production of supersymmetric particles, namely gluinos, top squarks, and tau sleptons, and of the Drell-Yan pair production of fourth generation (τ′) leptons with an electric charge equal to or twice the absolute value of the electron charge (e). An interpretation of a Z’ boson decaying to two τ′ leptons with an electric charge equal to 2e is presented for the first time. The 95% confidence upper limits on the production cross section are extracted for each of these hypothetical particles.« less

A search is presented for fractionally charged particles with charges below 1⁢𝑒, using their small energy loss in the tracking detector as a key variable to observe a signal. The analyzed dataset corresponds to an integrated luminosity of 138 fb⁻¹ of proton-proton collisions collected at $$\sqrt{𝑠}$$ = 13 TeV in 2016–2018 at the CERN LHC. This is the first search at the LHC for new particles with a charge between 𝑒/3 and 0.9⁢𝑒, including an extension of previous results at a charge of 2⁢𝑒/3. Masses up to 640 GeV and charges as low as 𝑒/3 are excluded at 95% confidencemore » level. These are the most stringent limits to date for the considered Drell-Yan-like production mode.« less