Single top quark events produced in the t channel are used to set limits on anomalous Wtb couplings and to search for top quark flavour-changing neutral current (FCNC) interactions. The data taken with the CMS detector at the LHC in proton-proton collisions at √ s = 7 and 8 TeV correspond to integrated luminosities of 5.0 and 19.7 fb −1 , respectively. The analysis is performed using events with one muon and two or three jets. A Bayesian neural network technique is used to discriminate between the signal and backgrounds, which are observed to be consistent with the standard model prediction. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left-and righthanded tensor Wtb couplings are measured to be |f R V | < 0.16, |f L T | < 0.057, and −0.049 < f R T < 0.048, respectively. For the FCNC couplings κ tug and κ tcg , the 95% CL upper limits on coupling strengths are |κ tug |/Λ < 4.1 × 10 −3 TeV −1 and |κ tcg |/Λ < 1.where Λ is the scale for new physics, and correspond to upper limits on the branching fractions of 2.0 × 10 −5 and 4.1 × 10 −4 for the decays t → ug and t → cg, respectively. The CMS collaboration 26 IntroductionSingle top quark (t) production provides ways to investigate aspects of top quark physics that cannot be studied with tt events [1]. The theory of electroweak interactions predicts three mechanisms for producing single top quarks in hadron-hadron collisions. At leading order (LO), these are classified according to the virtuality of the W boson propagation in t-channel, s-channel, or associated tW production [2]. Single top quark production in all channels is directly related to the squared modulus of the Cabibbo-Kobayashi-Maskawa matrix element V tb . As a consequence, it provides a direct measurement of this quantity and thereby a check of the standard model (SM Collaborations. There are two complementary strategies to search for FCNC in single top quark production. A search can be performed in the s channel for resonance production through the fusion of a gluon (g) with an up (u) or charm (c) quark, as was the case in analyses by the CDF and ATLAS Collaborations. However, as pointed out by the D0 Collaboration, the s-channel production rate is proportional to the square of the FCNC coupling parameter and is therefore expected to be small [22]. On the other hand, the t-channel cross section and its corresponding kinematic properties have been measured accurately at the LHC [24][25][26], with an important feature being that the t-channel signature contains a light-quark jet produced in association with the single top quark. This light-quark jet can be used to search for deviations from the SM prediction caused by FCNC in the top quark sector. This strategy was applied by the D0 Collaboration [22], as well as in our analysis. Models that have contributions from FCNC in the production of single top quarks can have sizable deviations relative to SM predictions. Processes with FCNC vertices in the decay of the top quark are negligible. In contrast, the ...

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...

Four-lepton production in proton-proton collisions, pp → (Z/γ * ) (Z/γ * ) → + − + − , where , = e or µ, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.6 fb −1 . The ZZ production cross section, σ(pp → ZZ) = 14.6 +1.9 −1.8 (stat) +0.5 −0.3 (syst) ± 0.2 (theo) ± 0.4 (lumi) pb, is measured for events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 < m + − , m + − < 120 GeV. The Z boson branching fraction to four leptons is measured to be B(Z → + − + − ) = 4.9 +0.8 −0.7 (stat) +0.3 −0.2 (syst) +0.2 −0.1 (theo) ± 0.1 (lumi) × 10 −6 for the four-lepton invariant mass in the range 80 < m + − + − < 100 GeV and dilepton mass m + − > 4 GeV for all opposite-sign, same-flavor lepton pairs. The results are in agreement with standard model predictions.

Objective: This study was conducted to assess the clinical usability of the zero-echo time (ZTE) technique of MRI for evaluating bone changes of the temporomandibular joint (TMJ) in comparison with CBCT. Methods: Twenty patients with TMJ disorder who underwent both CBCT and MRI were randomly selected. CBCT images were obtained with an Alphard 3030 device (Asahi Roentgen Ind., Co. Ltd, Kyoto, Japan). MRIs were obtained using a 3.0 T scanner (Pioneer; GE Healthcare, Waukesha, WI, USA) and a 21-channel head coil. An isotropic three-dimensional proton-density-weighted ZTE sequence was acquired. Two radiologists evaluated 40 joints of 20 patients for the presence of the following osseous changes: flattening, erosion, osteophyte and sclerosis of the condyle; and flattening, erosion and sclerosis of the articular fossa. CBCT and ZTE-MRI assessments were performed at a 2-month interval. The prevalence-adjusted and bias-adjusted κ statistic was used to analyse interexaminer and intraexaminer agreement and the agreement between ZTE-MRI and CBCT. Results: Intraexaminer and interexaminer agreement analyses of ZTE-MRI showed high reproducibility (κ>0.80), which was comparable to that of CBCT. Flattening, osteophyte and sclerosis of the condyle and all types of bone changes in the mandibular fossa showed nearly perfect agreement between CBCT and ZTE-MRI (κ = 0.80–0.90). Erosion of the condyle showed substantial agreement between both sets of images (κ = 0.65–0.70). Conclusions: It is suggested that ZTE-MRI provides clinically reliable images for bone assessment in TMJ disorder. MRI may become a beneficial diagnostic tool for patients with both TMJ disc and bone pathology, with advantages involving medical costs and radiation dose.

The relative modification of the prompt ψ(2S) and J/ψ yields from pp to PbPb collisions, at the center of mass energy of 5.02 TeV per nucleon pair, is presented. The analysis is based on pp and PbPb data samples collected by the CMS experiment at the LHC in 2015, corresponding to integrated luminosities of 28.0 pb −1 and 464 µb −1 , respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, (N ψ(2S) /N J/ψ ) PbPb /(N ψ(2S) /N J/ψ ) pp , is determined as a function of PbPb collision centrality and charmonium transverse momentum p T , in two kinematic intervals: |y| < 1.6 covering 6.5 < p T < 30 GeV/c and 1.6 < |y| < 2.4 covering 3 < p T < 30 GeV/c. The centrality-integrated double ratios are 0.36 ± 0.08 (stat) ± 0.05 (syst) in the first interval and 0.24 ± 0.22 (stat) ± 0.09 (syst) in the second. The double ratio is lower than unity in all the measured bins, suggesting that the ψ(2S) yield is more suppressed than the J/ψ yield in the explored phase space.