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Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss [Formula omitted] and the four-momentum transfer squared t. Both processes [Formula omitted] and [Formula omitted], i.e. with the proton scattering to either side of the interaction point, are measured, where [Formula omitted] includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at [Formula omitted] during a dedicated run with [Formula omitted] at low instantaneous luminosity and correspond to an integrated luminosity of [Formula omitted]. The single-diffractive dijet cross section [Formula omitted], in the kinematic region [Formula omitted], [Formula omitted], with at least two jets with transverse momentum [Formula omitted], and pseudorapidity [Formula omitted], is [Formula omitted]. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of [Formula omitted], is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range [Formula omitted], is [Formula omitted], where [Formula omitted] and [Formula omitted] are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.

A data sample of events from proton-proton collisions with at least two jets, and two isolated same-sign or three or more charged leptons, is studied in a search for signatures of new physics phenomena. The data correspond to an integrated luminosity of [Formula omitted] at a center-of-mass energy of [Formula omitted], collected in 2016-2018 by the CMS experiment at the LHC. The search is performed using a total of 168 signal regions defined using several kinematic variables. The properties of the events are found to be consistent with the expectations from standard model processes. Exclusion limits at 95% confidence level are set on cross sections for the pair production of gluinos or squarks for various decay scenarios in the context of supersymmetric models conserving or violating R parity. The observed lower mass limits are as large as [Formula omitted] for gluinos and [Formula omitted] for top and bottom squarks. To facilitate reinterpretations, model-independent limits are provided in a set of simplified signal regions.

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 [Formula omitted] collisions at nucleon-nucleon center-of-mass energies [Formula omitted] and 5.02 [Formula omitted] 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.

Normalised multi-differential cross sections for top quark pair ( [Formula omitted]) production are measured in proton-proton collisions at a centre-of-mass energy of 13 [Formula omitted] using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of [Formula omitted]. The double-differential [Formula omitted] cross section is measured as a function of the kinematic properties of the top quark and of the [Formula omitted] system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the [Formula omitted] system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength [Formula omitted] and the top quark pole mass ( [Formula omitted]) using several sets of parton distribution functions (PDFs). The measurement of [Formula omitted] exploits the sensitivity of the [Formula omitted] invariant mass distribution to [Formula omitted] near the production threshold. Furthermore, a simultaneous fit of the PDFs, [Formula omitted], and [Formula omitted] is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of [Formula omitted] and [Formula omitted]. The values [Formula omitted] and [Formula omitted] are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the [Formula omitted] production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of [Formula omitted] of the order of [Formula omitted], which can be regarded as additional theoretical uncertainty in the current [Formula omitted] extraction.

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 13 [Formula omitted] by the CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9 [Formula omitted], 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 ( [Formula omitted]), rapidity, and polarisation angle, the charged lepton [Formula omitted] and rapidity, and the [Formula omitted] of the [Formula omitted] boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and [Formula omitted] 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 [Formula omitted], in agreement with the standard model prediction.

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

A search is presented for [Formula omitted] slepton pairs produced in proton-proton collisions at a center-of-mass energy of 13 [Formula omitted]. The search is carried out in events containing two [Formula omitted] leptons in the final state, on the assumption that each [Formula omitted] slepton decays primarily to a [Formula omitted] lepton and a neutralino. Events are considered in which each [Formula omitted] lepton decays to one or more hadrons and a neutrino, or in which one of the [Formula omitted] 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 [Formula omitted]. 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 [Formula omitted] slepton pair production in various models for [Formula omitted] slepton masses between 90 and 200 [Formula omitted] and neutralino masses of 1, 10, and 20 [Formula omitted]. In the case of purely left-handed [Formula omitted] slepton production and decay to a [Formula omitted] lepton and a neutralino with a mass of 1 [Formula omitted], the strongest limit is obtained for a [Formula omitted] slepton mass of 125 [Formula omitted] at a factor of 1.14 larger than the theoretical cross section.

The standard model (SM) production of four top quarks ( [Formula omitted]) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 [Formula omitted] at a center-of-mass energy of 13 [Formula omitted]. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the [Formula omitted] signal are respectively 2.6 and 2.7 standard deviations, and the [Formula omitted] cross section is measured to be [Formula omitted]. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, [Formula omitted], yielding a limit of [Formula omitted] at [Formula omitted] confidence level, where [Formula omitted] is the SM value of [Formula omitted]. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, [Formula omitted]. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 [Formula omitted] and 350-550 [Formula omitted] for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

A search for [Formula omitted] 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 [Formula omitted]. The analyzed data set corresponds to an integrated luminosity of [Formula omitted], 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 [Formula omitted] production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is [Formula omitted].

Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of proton-proton collisions at a center-of-mass energy of [Formula omitted], collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 137 [Formula omitted]. The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable [Formula omitted] for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving R-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.