Search for resonant t(t)over-bar production in proton-proton collisions at root s=13 TeV

A search for a heavy resonance decaying into a top quark and antiquark (t t \uaf) pair is performed using proton-proton collisions at 1a 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 121 . 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 t t \uaf pair are calculated. Limits are derived for a leptophobic topcolor Z \u2032 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 t t \uaf resonances

Measurements with silicon photomultipliers of dose-rate effects in the radiation damage of plastic scintillator tiles in the CMS hadron endcap calorimeter

Measurements are presented of the reduction of signal output due to radiation damage for two types of plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb-1. The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: A laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions. Results from several irradiation campaigns using 60Co sources are also discussed. The damage is presented as a function of dose rate. Within the range of these measurements, for a fixed dose the damage increases with decreasing dose rate

Observation of nuclear modifications in W-+/- boson production in pPb collisions at root s(NN)=8.16 TeV

The production of W\ub1 bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 1asNN=8.16TeV. Measurements are performed in the W\ub1\u2192\u3bc\ub1\u3bd\u3bc channel using a data sample corresponding to an integrated luminosity of 173.4\ub16.1nb 121, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame |\u3b7lab\u3bc|<2.4 and transverse momentum pT\u3bc>25GeV/c. The W\ub1 boson differential cross sections, muon charge asymmetry, and the ratios of W\ub1 boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits