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Studies of Charm Quark Diffusion inside Jets Using Pb-Pb and pp Collisions at root s(NN)=5.02 TeV
(2020)Physical Review LettersThe first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with pjetT>60 GeV/c and D0 mesons with pDT>4 GeV/c in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of √sNN=5.02 TeV, recorded by the CMS detector at the LHC. The radial distribution of D0 mesons with respect to the jet axis is sensitive to ...Journal Article -
Measurement of CKM matrix elements in single top quark t-channel production in proton-proton collisions at s=13 TeV
(2020)Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy PhysicsThe first direct, model-independent measurement is presented of the modulus of the Cabibbo–Kobayashi–Maskawa (CKM) matrix elements |η|Vtb, |η|Vtd, and |η|Vts, in final states enriched in single top quark t-channel events. The analysis uses proton-proton collision data from the LHC, collected during 2016 by the CMS experiment, at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Processes directly ...Journal Article -
Pileup mitigation at CMS in 13 TeV data
(2020)Journal of InstrumentationWith increasing instantaneous luminosity at the LHC come additional reconstruction challenges. At high luminosity, many collisions occur simultaneously within one proton-proton bunch crossing. The isolation of an interesting collision from the additional "pileup" collisions is needed for effective physics performance. In the CMS Collaboration, several techniques capable of mitigating the impact of these pileup collisions have been developed. ...Journal Article -
Measurements of (tt)over-barH Production and the CP Structure of the Yukawa Interaction between the Higgs Boson and Top Quark in the Diphoton Decay Channel
(2020)Physical Review LettersThe first observation of the (tt) over barH process in a single Higgs boson decay channel with the full reconstruction of the final state (H -> gamma gamma) is presented, with a significance of 6.6 standard deviations (sigma). The CP structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2 sigma. The measurements are based on a sample of protonproton ...Journal Article -
Study of central exclusive π+π− production in proton-proton collisions at √s=5.02 and 13TeV
(2020)The European Physical Journal CCentral exclusive and semiexclusive production of π+π− pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13 TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, ...Journal Article -
Search for disappearing tracks in proton-proton collisions at s=13TeV
(2020)Physics Letters BA search is presented for long-lived charged particles that decay within the volume of the silicon tracker of the CMS experiment. Such particles can produce events with an isolated track that is missing hits in the outermost layers of the silicon tracker, and is also associated with little energy deposited in the calorimeters and no hits in the muon detectors. The search for events with this “disappearing track” signature is performed in ...Journal Article -
Search for dijet resonances using events with three jets in proton-proton collisions at s=13TeV
(2020)Physics Letters BA search for a narrow resonance with a mass between 350 and 700 GeV, and decaying into a pair of jets, is performed using proton-proton collision events containing at least three jets. The data sample corresponds to an integrated luminosity of 18.3 fb−1 recorded at s=13TeV with the CMS detector. Data are collected with a technique known as “data scouting”, in which the events are reconstructed, selected, and recorded at a high rate in a ...Journal Article -
A measurement of the Higgs boson mass in the diphoton decay channel
(2020)Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy PhysicsA measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9fb−1 of proton-proton collision data collected during the 2016 LHC running period, with the CMS detector at a centre-of-mass energy of 13 TeV. A refined detector calibration and new analysis techniques have been used to improve the precision of this measurement. The Higgs boson mass is measured to be mH=125.78±0.26GeV. ...Journal Article -
Identification of heavy, energetic, hadronically decaying particles using machine-learning techniques
(2020)Journal of InstrumentationMachine-learning (ML) techniques are explored to identify and classify hadronic decays of highly Lorentz-boosted W/Z/Higgs bosons and top quarks. Techniques without ML have also been evaluated and are included for comparison. The identification performances of a variety of algorithms are characterized in simulated events and directly compared with data. The algorithms are validated using proton-proton collision data at root S = 13 TeV, ...Journal Article -
Strange hadron production in pp and pPb collisions at sNN =5.02 TeV
(2020)Physical Review CThe transverse momentum (pT) distributions of Λ, Ξ-, and ω- baryons, their antiparticles, and KS0 mesons are measured in proton-proton (pp) and proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV over a broad rapidity range. The data, corresponding to integrated luminosities of 40.2 nb-1 and 15.6 μb-1 for pp and pPb collisions, respectively, were collected by the CMS experiment. The nuclear modification ...Journal Article