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A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016-2018 and corresponding to an integrated luminosity of 138 fb$^{-1}$. No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W' bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W' boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak $W$ parameter, are presented using LHC data for the first time. These results together with those from the direct W' resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements.

Events with no charged particles produced between the two leading jets are studied in proton-proton collisions at

A search is presented for additional scalar (H) or pseudoscalar (A) Higgs bosons decaying to a top quark pair in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set analyzed corresponds to an integrated luminosity of 35.9 fb − 1 collected by the CMS experiment at the LHC. Final states with one or two charged leptons are considered. The invariant mass of the reconstructed top quark pair system and variables that are sensitive to the spin of the particles decaying into the top quark pair are used to search for signatures of the H or A bosons. The interference with the standard model top quark pair background is taken into account. A moderate signal-like deviation compatible with an A boson with a mass of 400 GeV is observed with a global significance of 1.9 standard deviations. New stringent constraints are reported on the strength of the coupling of the hypothetical bosons to the top quark, with the mass of the bosons ranging from 400 to 750 GeV and their total relative width from 0.5 to 25%. The results of the search are also interpreted in a minimal supersymmetric standard model scenario. Values of m A from 400 to 700 GeV are probed, and a region with values of tan β below 1.0 to 1.5, depending on m A , is excluded at 95% confidence level.

This paper reports on a search for an extension to the scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy$$ \\sqrt{s} $$s = 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb − 1 . Data and predictions from the standard model are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model.

A search is presented for$${\\uptau }_{}^{}$$τ slepton pairs produced in proton–proton collisions at a center-of-mass energy of 13$$\\,\\text {TeV}$$TeV . The search is carried out in events containing two$${\\uptau }_{}^{}$$τ leptons in the final state, on the assumption that each$${\\uptau }_{}^{}$$τ slepton decays primarily to a$${\\uptau }_{}^{}$$τ lepton and a neutralino. Events are considered in which each$${\\uptau }_{}^{}$$τ lepton decays to one or more hadrons and a neutrino, or in which one of the$${\\uptau }_{}^{}$$τ leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2$$\\,\\text {fb}^{-1}$$fb - 1 . The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for$${\\uptau }_{}^{}$$τ slepton pair production in various models for$${\\uptau }_{}^{}$$τ slepton masses between 90 and 200$$\\,\\text {GeV}$$GeV and neutralino masses of 1, 10, and 20$$\\,\\text {GeV}$$GeV . In the case of purely left-handed$${\\uptau }_{}^{}$$τ slepton production and decay to a$${\\uptau }_{}^{}$$τ lepton and a neutralino with a mass of 1$$\\,\\text {GeV}$$GeV , the strongest limit is obtained for a$${\\uptau }_{}^{}$$τ slepton mass of 125$$\\,\\text {GeV}$$GeV at a factor of 1.14 larger than the theoretical cross section.

A search for$$\\text {W}\\text {W}$$WW production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a center-of-mass energy of$$13\\,\\text {TeV} $$13 TeV . The analyzed data set corresponds to an integrated luminosity of$$77.4{\\,\\text {fb}^{-1}} $$77.4 fb - 1 , collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for$$\\text {W}\\text {W}$$WW production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is$$1.41\\pm 0.28\\,\\text {(stat)} \\pm 0.28\\,\\text {(syst)} \\,\\text {pb} $$1.41 ± 0.28 (stat) ± 0.28 (syst) pb .

A search for a heavy resonance decaying into a top quark and antiquark$$ \\left(\\mathrm{t}\\overline{\\mathrm{t}}\\right) $$t t ¯ pair is performed using proton-proton collisions at$$ \\sqrt{s}=13 $$s = 13 TeV. The search uses the data set collected with the CMS detector in 2016, which corresponds to an integrated luminosity of 35.9 fb −1 . The analysis considers three exclusive final states and uses reconstruction techniques that are optimized for top quarks with high Lorentz boosts, which requires the use of nonisolated leptons and jet substructure techniques. No significant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to a$$ \\mathrm{t}\\overline{\\mathrm{t}} $$t t ¯ pair are calculated. Limits are derived for a leptophobic topcolor Z ′ resonance with widths of 1, 10, and 30%, relative to the mass of the resonance, and exclude masses up to 3.80, 5.25, and 6.65 TeV, respectively. Kaluza-Klein excitations of the gluon in the Randall-Sundrum model are excluded up to 4.55 TeV. To date, these are the most stringent limits on$$ \\mathrm{t}\\overline{\\mathrm{t}} $$t t ¯ resonances.

Results of a search for nonresonant production of Higgs boson pairs, with each Higgs boson decaying to a$$ \\mathrm{b}\\overline{\\mathrm{b}} $$b b ¯ pair, are presented. This search uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb −1 , collected by the CMS detector at the LHC. No signal is observed, and a 95% confidence level upper limit of 847 fb is set on the cross section for standard model nonresonant Higgs boson pair production times the squared branching fraction of the Higgs boson decay to a$$ \\mathrm{b}\\overline{\\mathrm{b}} $$b b ¯ pair. The same signature is studied, and upper limits are set, in the context of models of physics beyond the standard model that predict modified couplings of the Higgs boson.

Measurements of differential top quark pair$$ \\mathrm{t}\\overline{\\mathrm{t}} $$t t ¯ cross sections using events produced in proton-proton collisions at a centre-of-mass energy of 13 TeV containing two oppositely charged leptons are presented. The data were recorded by the CMS experiment at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb −1 . The differential cross sections are presented as functions of kinematic observables of the top quarks and their decay products, the$$ \\mathrm{t}\\overline{\\mathrm{t}} $$t t ¯ system, and the total number of jets in the event. The differential cross sections are defined both with particle-level objects in a fiducial phase space close to that of the detector acceptance and with parton-level top quarks in the full phase space. All results are compared with standard model predictions from Monte Carlo simulations with next-to-leading-order (NLO) accuracy in quantum chromodynamics (QCD) at matrix-element level interfaced to parton-shower simulations. Where possible, parton-level results are compared to calculations with beyond-NLO precision in QCD. Significant disagreement is observed between data and all predictions for several observables. The measurements are used to constrain the top quark chromomagnetic dipole moment in an effective field theory framework at NLO in QCD and to extract$$ \\mathrm{t}\\overline{\\mathrm{t}} $$t t ¯ and leptonic charge asymmetries.