Constraints on models of scalar and vector leptoquarks decaying to a quark and a neutrino at √ s = 13 TeVThe CMS Collaboration * AbstractThe results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the M T2 variable. The analysis uses proton-proton collision data at √ s = 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb −1 . Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to tν, and 50% to bτ, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to tν, LQ masses below 1530 GeV are excluded assuming the Yang-Mills case with coupling κ = 1, or 1115 GeV in the minimal coupling case κ = 0, placing the most stringent constraint to date from pair production of vector LQs.Published in Physical Review D as

A search for low mass narrow vector resonances decaying into quark-antiquark pairs is presented. The analysis is based on data collected in 2017 with the CMS detector at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 41.1 fb −1. The results of this analysis are combined with those of an earlier analysis based on data collected at the same collision energy in 2016, corresponding to 35.9 fb −1. Signal candidates will be recoiling against initial state radiation and are identified as energetic, large-radius jets with two pronged substructure. The invariant jet mass spectrum is probed for a potential narrow peaking signal over a smoothly falling background. No evidence for such resonances is observed within the mass range of 50-450 GeV. Upper limits at the 95% confidence level are set on the coupling of narrow resonances to quarks, as a function of the resonance mass. For masses between 50 and 300 GeV these are the most sensitive limits to date. This analysis extends the earlier search to a mass range of 300-450 GeV, which is probed for the first time with jet substructure techniques.

Results are reported for the B 0 s → µ + µ − branching fraction and effective lifetime and from a search for the decay B 0 → µ + µ −. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7 TeV (5 fb −1), 8 TeV (20 fb −1), and 13 TeV (36 fb −1). The branching fractions are determined by measuring event yields relative to B + → J/ψK + decays (with J/ψ → µ + µ −), which results in the reduction of many of the systematic uncertainties. The decay B 0 s → µ + µ − is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be B(B 0 s → µ + µ −) = [2.9 ± 0.7(exp) ± 0.2(frag)] × 10 −9 , where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the B 0 s and the B + fragmentation functions. No significant excess is observed for the decay B 0 → µ + µ − , and an upper limit of B(B 0 → µ + µ −) < 3.6 × 10 −10 is obtained at 95% confidence level. The B 0 s → µ + µ − effective lifetime is measured to be τ µ + µ − = 1.70 +0.61 −0.44 ps. These results are consistent with standard model predictions.

A search is presented for the production of vector-like quark pairs, TT or YY, with electric charge of 2/3 (T) or −4/3 (Y), in proton-proton collisions at √ s = 13 TeV. The data were collected by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.8 fb −1 . The T and Y quarks are assumed to decay exclusively to a W boson and a b quark. The search is based on events with a single isolated electron or muon, large missing transverse momentum, and at least four jets with large transverse momenta. In the search, a kinematic reconstruction of the final state observables is performed, which would permit a signal to be detected as a narrow mass peak (≈7% resolution). The observed number of events is consistent with the standard model prediction. Assuming strong pair production of the vectorlike quarks and a 100% branching fraction to bW, a lower limit of 1295 GeV at 95% confidence level is set on the T and Y quark masses. 3 Event samplesgrooming algorithm [17]. These resolved subjets are counted individually when selecting fourjet final states and contribute separately in the kinematic fit (see Section 5). Events with leptonically decaying W bosons include those decaying into a τ lepton (in the decay sequence W → τ + ν, τ → + 2ν). They are treated in the same way as events with direct decays to muons or electrons. The CMS detectorThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the superconducting solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL) with preshower detector, and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity [18] coverage provided by the barrel and endcap detectors. The detector is nearly hermetic, allowing for momentum balance measurements in the plane transverse to the beam direction. Muons are detected in gas-ionization chambers embedded in the steel flux-return yoke outside the solenoid.A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [18]. Event samplesThe analysis is based on integrated luminosities of 35.8 fb −1 in the muon channel and 35.6 fb −1 in the electron channel. The trigger providing the muon data sample requires the presence of at least one muon with p T > 50 GeV and pseudorapidity |η| < 2.5. For the electron data sample, events are required to have a single isolated electron with p T > 32 GeV and |η| < 2.1.Simulated event samples are used to estimate the signal efficiencies and background contributions. The following background production processes are modeled: tt+jets; W+jets and Z+jets (single boson production); single top quark via the tW, sand t-channel processes; WW, WZ, and ZZ (diboson production); and quantum chromodynamic (QCD) multijet production. The dominant background is from...

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