This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at s=13 TeV, corresponding to an integrated luminosity of 35.9 fb-1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250-3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.

A measurement is presented of differential cross sections for t-channel single top quark and antiquark production in proton–proton collisions at a centre-of-mass energy of 13Te by the CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9fb-1, events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum (p_T), rapidity, and polarisation angle, the charged lepton p_T and rapidity, and the p_T of the W boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and W boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be 0.440 ± 0.070 , in agreement with the standard model prediction.

A measurement is presented of the production of Formula Presented bosons that decay into two electrons or muons in association with jets, in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS Collaboration at the LHC with an integrated luminosity of Formula Presented. The differential cross sections are measured as a function of the transverse momentum (Formula Presented) of the Formula Presented boson and the transverse momentum and rapidities of the five jets with largest Formula Presented. The jet multiplicity distribution is measured for up to eight jets. The hadronic activity in the events is estimated using the scalar sum of the Formula Presented of all the jets. All measurements are unfolded to the stable-particle level and compared with predictions from various Monte Carlo event generators, as well as with expectations at leading and next-to-leading orders in perturbative quantum chromodynamics.

Measurements of prompt ψ(2S) meson production cross sections in proton–lead (pPb) and proton–proton (pp) collisions at a nucleon–nucleon center-of-mass energy of s_NN=5.02TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb⁻¹ and 28.0 pb⁻¹, respectively. The nuclear modification factor R_pPb is measured for prompt ψ(2S) in the transverse momentum range 4<p_T<30GeV/c and the center-of-mass rapidity range −2.4<y_CM<1.93. The results on ψ(2S) R_pPb are compared to the corresponding modification factor for prompt J/ψ mesons. The results point to different nuclear effects at play in the production of the excited charmonium state compared to the ground state, in the region of backward rapidity and for p_T<10GeV/c.

Measurements of the differential jet cross section are presented as a function of the jet mass in dijet events, in bins of jet transverse momentum, with and without a jet grooming algorithm. The data have been recorded by the CMS Collaboration in proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 2.3 fb⁻¹. The absolute cross sections show slightly different jet transverse momentum spectra in data and Monte Carlo event generators for the settings used. Removing this transverse momentum dependence, the normalized cross section for ungroomed jets is consistent with the prediction from Monte Carlo event generators for masses below 30% of the transverse momentum. The normalized cross section for groomed jets is measured with higher precision than the ungroomed cross section. Semi-analytical calculations of the jet mass beyond leading logarithmic accuracy are compared to data, as well as predictions at leading order and next-to-leading order, which include parton showering and hadronization. Overall, in the normalized cross section, the theoretical predictions agree with the measured cross sections within the uncertainties for masses from 10 to 30% of the jet transverse momentum.[Figure not available: see fulltext.].

Anisotropies in the initial energy density distribution of the quark-gluon plasma created in high energy heavy ion collisions lead to anisotropies in the azimuthal distributions of the final-state particles known as collective anisotropic flow. Fourier harmonic decomposition is used to quantify these anisotropies. The higher-order harmonics can be induced by the same order anisotropies (linear response) or by the combined influence of several lower order anisotropies (nonlinear response) in the initial state. The mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles are measured as functions of transverse momentum and centrality in PbPb collisions at nucleon-nucleon center-of-mass energies sNN=2.76 and 5.02TeV with the CMS detector. The results are compared with viscous hydrodynamic calculations using several different initial conditions, as well as microscopic transport model calculations. None of the models provides a simultaneous description of the mixed higher-order flow harmonics and nonlinear response coefficients.

The observation of the Λ_b ⁰→J/ψΛϕ decay is reported using proton-proton collision data collected at s=13TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60fb⁻¹. The ratio of the branching fractions B(Λ_b ⁰→J/ψΛϕ)/B(Λ_b ⁰→ψ(2S)Λ) is measured to be (8.26±0.90(stat)±0.68(syst)±0.11(B))×10⁻², where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of ϕ and ψ(2S) decays to the reconstructed final states.

A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb⁻¹, collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ, and considers pseudoscalar masses in the range 3.6 < m_a< 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of m_a, on the branching fraction (ℬ) for H → aa → μμττ, down to 1.5 (2.0) × 10⁻⁴ for m_H = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV. [Figure not available: see fulltext.].

A search for exotic Higgs boson decays to light pseudoscalars in the final state of two muons and two τ leptons is performed using proton-proton collision data recorded by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9 fb⁻¹. Masses of the pseudoscalar boson between 15.0 and 62.5 GeV are probed, and no significant excess of data is observed above the prediction of the standard model. Upper limits are set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different types of two-Higgs-doublet models extended with a complex scalar singlet.[Figure not available: see fulltext.].

A search for nonresonant excesses in the invariant mass spectra of electron and muon pairs is presented. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment in 2016, corresponding to a total integrated luminosity of 36 fb ⁻¹ . No significant deviation from the standard model is observed. Limits are set at 95% confidence level on energy scales for two general classes of nonresonant models. For a class of fermion contact interaction models, lower limits ranging from 20 to 32 TeV are set on the characteristic compositeness scale Λ. For the Arkani-Hamed, Dimopoulos, and Dvali model of large extra dimensions, the first results in the dilepton final state at 13 TeV are reported, and values of the ultraviolet cutoff parameter Λ _T below 6.9 TeV are excluded. A combination with recent CMS diphoton results improves this exclusion to Λ _T below 7.7 TeV, providing the most sensitive limits to date in nonhadronic final states.[Figure not available: see fulltext.]

A search for dark matter particles is performed by looking for events with large transverse momentum imbalance and a recoiling Higgs boson decaying to either a pair of photons or a pair of τ leptons. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected at the CERN LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb⁻¹. No significant excess over the expected standard model background is observed. Upper limits at 95% confidence level are presented for the product of the production cross section and branching fraction in the context of two benchmark simplified models. For the Z^′-two-Higgs-doublet model (where Z^′ is a new massive boson mediator) with an intermediate heavy pseudoscalar particle of mass m_A = 300 GeV and m_DM = 100 GeV, the Z^′ masses from 550 GeV to 1265 GeV are excluded. For a baryonic Z^′ model, with m_DM = 1 GeV, Z^′ masses up to 615 GeV are excluded. Results are also presented for the spin-independent cross section for the dark matter-nucleon interaction as a function of the mass of the dark matter particle. This is the first search for dark matter particles produced in association with a Higgs boson decaying to two τ leptons.[Figure not available: see fulltext.].

A search for a heavy neutral lepton N of Majorana nature decaying into a W boson and a charged lepton is performed using the CMS detector at the LHC. The targeted signature consists of three prompt charged leptons in any flavor combination of electrons and muons. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV, with an integrated luminosity of 35.9 fb-1. The search is performed in the N mass range between 1 GeV and 1.2 TeV. The data are found to be consistent with the expected standard model background. Upper limits are set on the values of |VeN|2 and |VμN|2, where V N is the matrix element describing the mixing of N with the standard model neutrino of flavor. These are the first direct limits for N masses above 500 GeV and the first limits obtained at a hadron collider for N masses below 40 GeV.

A search for new physics in top quark production is performed in proton-proton collisions at 13TeV. The data set corresponds to an integrated luminosity of 35.9fb-1 collected in 2016 with the CMS detector. Events with two opposite-sign isolated leptons (electrons or muons), and b quark jets in the final state are selected. The search is sensitive to new physics in top quark pair production and in single top quark production in association with a W boson. No significant deviation from the standard model expectation is observed. Results are interpreted in the framework of effective field theory and constraints on the relevant effective couplings are set, one at a time, using a dedicated multivariate analysis. This analysis differs from previous searches for new physics in the top quark sector by explicitly separating t W from t t ¯ events and exploiting the specific sensitivity of the t W process to new physics.

A search for resonancelike structures in the Bs0π± invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at s=8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. The Bs0 mesons are reconstructed in the decay chain Bs0→J/ψφ, with J/ψ→μ+μ- and φ→K+K-. The Bs0π± invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed Bs0 and π± candidates. Upper limits are set on the relative production rates of the X(5568) and Bs0 states times the branching fraction of the decay X(5568)±→Bs0π±. In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into Bs0π±.

A search for the pair production of heavy fermionic partners of the top quark with charge 5/3 (X _5/3 ) is performed in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC. The data sample analyzed corresponds to an integrated luminosity of 35.9 fb ⁻¹ . The X _5/3 quark is assumed always to decay into a top quark and a W boson. Both the right-handed and left-handed X _5/3 couplings to the W boson are considered. Final states with either a pair of same-sign leptons or a single lepton are studied. No significant excess of events is observed above the expected standard model background. Lower limits at 95% confidence level on the X _5/3 quark mass are set at 1.33 and 1.30 TeV respectively for the case of right-handed and left-handed couplings to W bosons in a combination of the same-sign dilepton and single-lepton final states.[Figure not available: see fulltext.]

The transverse momentum spectra of D0 mesons from b hadron decays are measured at midrapidity (|y|<1) in pp and Pb-Pb collisions at a nucleon-nucleon center of mass energy of 5.02 TeV with the CMS detector at the LHC. The D0 mesons from b hadron decays are distinguished from prompt D0 mesons by their decay topologies. In Pb-Pb collisions, the B?D0 yield is found to be suppressed in the measured pT range from 2 to 100 GeV/c as compared to pp collisions. The suppression is weaker than that of prompt D0 mesons and charged hadrons for pT around 10 GeV/c. While theoretical calculations incorporating partonic energy loss in the quark-gluon plasma can successfully describe the measured B?D0 suppression at higher pT, the data show an indication of larger suppression than the model predictions in the range of 2<pT<5 GeV/c.