Publications
1517 results found
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Measurement of the ratio B(B-s(0) -> J/psi f(0)(980))/B(B-s(0) -> J/psi phi(1020)) in pp collisions at root s=7 TeV, Physics Letters B, Vol: 756, Pages: 84-102, ISSN: 0370-2693
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for single production of scalar leptoquarks in proton-proton collisions at √s=8 TeV, Physical Review D, Vol: 93, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for pair production of first and second generation leptoquarks in proton-proton collisions at √s=8 TeV, Physical Review D, Vol: 93, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Correlations between jets and charged particles in PbPb and pp collisions at root s(NN)=2.76 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
The quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 μb−1 and 5.3 pb−1, respectively, collected at sNN−−−√=2.76sNN=2.76 TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (Δη) and relative azimuthal angle (Δϕ) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum (p T) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in p T, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle p T. A centrality-dependent excess of low-p T particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-p T particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of Δη ≈ 1 and Δϕ ≈ 1.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for a massive resonance decaying into a Higgs boson and a W or Z boson in hadronic final states in proton-proton collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Measurement of the charge asymmetry in top quark pair production in pp collisions at √s=8 TeV using a template method, Physical Review D, Vol: 93, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for W′ → tb in proton-proton collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for Narrow Resonances Decaying to Dijets in Proton-Proton Collisions at √s=13 TeV, Physical Review Letters, Vol: 116, ISSN: 1079-7114
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Measurement of the Top Quark Pair Production Cross Section in Proton-Proton Collisions at √s=13 TeV, Physical Review Letters, Vol: 116, ISSN: 1079-7114
The top quark pair production cross section is measured for the first time in proton-proton collisions at s√=13 TeV by the CMS experiment at the CERN LHC, using data corresponding to an integrated luminosity of 43 pb−1. The measurement is performed by analyzing events with at least one electron and one muon of opposite charge, and at least two jets. The measured cross section is 746±58(stat)±53(syst)±36(lumi) pb, in agreement with the expectation from the standard model.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for W ' decaying to tau lepton and neutrino in proton-proton collisions at root s=8 TeV, Physics Letters B, Vol: 755, Pages: 196-216, ISSN: 0370-2693
The first search for a heavy charged vector boson in the final state with a tau lepton and a neutrino is reported, using 19.7 fb−1 of LHC data at View the MathML source. A signal would appear as an excess of events with high transverse mass, where the standard model background is low. No excess is observed. Limits are set on a model in which the W′ decays preferentially to fermions of the third generation. These results substantially extend previous constraints on this model. Masses below 2.0 to 2.7 TeV are excluded, depending on the model parameters. In addition, the existence of a W′ boson with universal fermion couplings is excluded at 95% confidence level, for W′ masses below 2.7 TeV. For further reinterpretation a model-independent limit on potential signals for various transverse mass thresholds is also presented.
Zabi A, Beaudette F, Cadamuro L, et al., 2016, Triggering on electrons, jets and tau leptons with the CMS upgraded calorimeter trigger for the LHC RUN II, Topical Workshop on Electronics for Particle Physics 2015, Publisher: IOP Publishing, ISSN: 1748-0221
The Compact Muon Solenoid (CMS) experiment has implemented a sophisticated two-level online selection system that achieves a rejection factor of nearly 105. During Run II, the LHC will increase its centre-of-mass energy up to 13 TeV and progressively reach an instantaneous luminosity of 2 × 1034 cm−2 s−1. In order to guarantee a successful and ambitious physics programme under this intense environment, the CMS Trigger and Data acquisition (DAQ) system has been upgraded. A novel concept for the L1 calorimeter trigger is introduced: the Time Multiplexed Trigger (TMT) . In this design, nine main processors receive each all of the calorimeter data from an entire event provided by 18 preprocessors. This design is not different from that of the CMS DAQ and HLT systems. The advantage of the TMT architecture is that a global view and full granularity of the calorimeters can be exploited by sophisticated algorithms. The goal is to maintain the current thresholds for calorimeter objects and improve the performance for their selection. The performance of these algorithms will be demonstrated, both in terms of efficiency and rate reduction. The callenging aspects of the pile-up mitigation and firmware design will be presented.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Reconstruction and identification of tau lepton decays to hadrons and nu(tau) at CMS, Journal of Instrumentation, Vol: 11, ISSN: 1748-0221
This paper describes the algorithms used by the CMS experiment to reconstruct and identify τ → hadrons + ντ decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1. The algorithms achieve an identification efficiency of 50–60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for the production of an excited bottom quark decaying to tW in proton-proton collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Study of B Meson Production in p+Pb Collisions at √sNN=5.02 TeV Using Exclusive Hadronic Decays, Physical Review Letters, Vol: 116, ISSN: 1079-7114
Kreis B, Berryhill J, Cavanaugh R, et al., 2016, Run 2 upgrades to the CMS Level-1 calorimeter trigger, Journal of Instrumentation, Vol: 11, ISSN: 1748-0221
The CMS Level-1 calorimeter trigger is being upgraded in two stages to maintain performance as the LHC increases pile-up and instantaneous luminosity in its second run. In the first stage, improved algorithms including event-by-event pile-up corrections are used. New algorithms for heavy ion running have also been developed. In the second stage, higher granularity inputs and a time-multiplexed approach allow for improved position and energy resolution. Data processing in both stages of the upgrade is performed with new, Xilinx Virtex-7 based AMC cards.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for vectorlike charge 2/3 T quarks in proton-proton collisions at √(s)=8 TeV, Physical Review D, Vol: 93, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Observation of top quark pairs produced in association with a vector boson in pp collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Transverse momentum spectra of inclusive b jets in pPb collisions atv root s(NN)=5.02 TeV, Physics Letters B, Vol: 754, Pages: 59-80, ISSN: 0370-2693
We present a measurement of b jet transverse momentum (pT) spectra in proton-lead (pPb) collisions using a dataset corresponding to about 35 nb−1 collected with the CMS detector at the LHC. Jets from b quark fragmentation are found by exploiting the long lifetime of hadrons containing a b quark through tagging methods using distributions of the secondary vertex mass and displacement. Extracted cross sections for b jets are scaled by the effective number of nucleon–nucleon collisions and are compared to a reference obtained from pythia simulations of pp collisions. The pythia-based estimate of the nuclear modification factor is found to be View the MathML source averaged over all jets with pT between 55 and 400 GeV/c and with |ηlab|<2. We also compare this result to predictions from models using perturbative calculations in quantum chromodynamics.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for a very light NMSSM Higgs boson produced in decays of the 125 GeV scalar boson and decaying into τ leptons in pp collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Measurement of differential cross sections for Higgs boson production in the diphoton decay channel in pp collisions at s√=8TeV, European Physical Journal C, Vol: 76, ISSN: 1434-6052
A measurement is presented of differential cross sections for Higgs boson (H) production in pp collisions at s√=8s=8 TeVTeV . The analysis exploits the H→γγH→γγ decay in data corresponding to an integrated luminosity of 19.7 fb-1fb-1 collected by the CMS experiment at the LHC. The cross section is measured as a function of the kinematic properties of the diphoton system and of the associated jets. Results corrected for detector effects are compared with predictions at next-to-leading order and next-to-next-to-leading order in perturbative quantum chromodynamics, as well as with predictions beyond the standard model. For isolated photons with pseudorapidities |η|<2.5|η|<2.5 , and with the photon of largest and next-to-largest transverse momentum ( pγTpTγ ) divided by the diphoton mass mγγmγγ satisfying the respective conditions of pγT/mγγ>1/3pTγ/mγγ>1/3 and >1/4>1/4 , the total fiducial cross section is 32±1032±10 \,fb\,fb .
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Search for resonant tt¯ production in proton-proton collisions at √s=8 TeV, Physical Review D, Vol: 93, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2016, Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at √sNN=2.76 TeV, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Search for a light charged Higgs boson decaying to c(s)over-bar in pp collisions at root s=8 TeV, Journal of High Energy Physics, Vol: 2015, ISSN: 1029-8479
A search for a light charged Higgs boson, originating from the decay of a topquark and subsequently decaying into a charm quark and a strange antiquark, is presented.The data used in the analysis correspond to an integrated luminosity of 19.7 fb−1recordedin proton-proton collisions at √s = 8 TeV by the CMS experiment at the LHC. The searchis performed in the process t¯t → W±bH∓b, where the W boson decays to a lepton (electron ¯or muon) and a neutrino. The decays lead to a final state comprising an isolated lepton,at least four jets and large missing transverse energy. No significant deviation is observedin the data with respect to the standard model predictions, and model-independent upperlimits are set on the branching fraction B(t → H+b), ranging from 1.2 to 6.5% for a chargedHiggs boson with mass between 90 and 160 GeV, under the assumption that B(H+ → c¯s)= 100%.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Search for a Higgs boson decaying into gamma*gamma -> ll gamma with low dilepton mass in pp collisions at root s=8 TeV, Physics Letters B, Vol: 753, Pages: 341-362, ISSN: 0370-2693
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Search for exotic decays of a Higgs boson into undetectable particles and one or more photons, Physics Letters B, Vol: 753, Pages: 363-388, ISSN: 0370-2693
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Angular analysis of the decay B-0 -> K*(0)mu(+)mu(-) from pp collisions at root s=8 TeV, Physics Letters B, Vol: 753, Pages: 424-448, ISSN: 0370-2693
The angular distributions and the differential branching fraction of the decay B0→K⁎(892)0μ+μ− are studied using data corresponding to an integrated luminosity of 20.5 fb−1 collected with the CMS detector at the LHC in pp collisions at View the MathML source. From 1430 signal decays, the forward–backward asymmetry of the muons, the K⁎(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions.
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Production of leading charged particles and leading charged-particle jets at small transverse momenta in pp collisions at √s=8 TeV, Physical Review D, Vol: 92, ISSN: 1550-7998
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Search for supersymmetry in the vector-boson fusion topology in proton-proton collisions at √s=8 TeV, Journal of High Energy Physics, Vol: 2015, ISSN: 1126-6708
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Search for neutral MSSM Higgs bosons decaying to mu(+) mu(-) in pp collisions at root s=7 and 8 TeV, Physics Letters B, Vol: 752, Pages: 221-246, ISSN: 0370-2693
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2015, Measurement of the differential cross section for top quark pair production in pp collisions at s√=8TeV, European Physical Journal C, Vol: 75, ISSN: 1434-6052
The normalized differential cross section for top quark pair ( tt¯tt¯ ) production is measured in pp collisions at a centre-of-mass energy of 8 TeVTeV at the CERN LHC using the CMS detector in data corresponding to an integrated luminosity of 19.7 fb−1fb−1 . The measurements are performed in the lepton ++ jets ( e/μe/μ ++ jets) and in the dilepton ( e+e−e+e− , μ+μ−μ+μ− , and e±μ∓e±μ∓ ) decay channels. The tt¯tt¯ cross section is measured as a function of the kinematic properties of the charged leptons, the jets associated to b quarks, the top quarks, and the tt¯tt¯ system. The data are compared with several predictions from perturbative quantum chromodynamic up to approximate next-to-next-to-leading-order precision. No significant deviations are observed relative to the standard model predictions.
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