Showing papers by "Amr Radi published in 2017"
••
TL;DR: In this article, the authors acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIEN-CIAS (Colombia); DAE and DST (India); IPM (Iran);
156 citations
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2264 more•Institutions (154)
TL;DR: In this paper, a search for narrow resonances in dielectron and dimuon invariant mass spectra has been performed using data obtained from proton-proton collisions at $\sqrt{s}=13$ TeV collected with the CMS detector.
111 citations
••
TL;DR: In this article, a search was performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying tau lepton, and at least two jets, using a sqrt(s) = 13 TeV pp collision data sample corresponding to an integrated luminosity of 12.9 inverse femtobarns collected with the LHC in 2016.
Abstract: A search is performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying tau lepton, and at least two jets, using a sqrt(s) = 13 TeV pp collision data sample corresponding to an integrated luminosity of 12.9 inverse femtobarns collected with the CMS detector at the LHC in 2016. The number of observed events is found to be in agreement with the standard model prediction. A limit is set at 95% confidence level on the product of the leptoquark pair production cross section and beta squared where beta is the branching fraction of leptoquark decay to a tau lepton and a bottom quark. Assuming beta = 1, third-generation leptoquarks with masses below 850 GeV are excluded at 95% confidence level. An additional search based on the same event topology involves heavy right-handed neutrinos, N[R], and right-handed W bosons, W[R] , arising in a left-right symmetric extension of the standard model. In this search, W[R] bosons are assumed to decay to a tau lepton and N[R] followed by the decay of the N[R] to a tau lepton and an off-shell W[R] boson. Assuming the mass of the right-handed neutrino to be half of the mass of the right-handed W boson, W[R] boson masses below 2.9 TeV are excluded at 95% confidence level. These results improve on the limits from previous searches for third-generation leptoquarks and heavy right-handed neutrinos with tau leptons in the final state.
100 citations
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2248 more•Institutions (147)
TL;DR: The nuclear modification factor and the azimuthal anisotropy coefficient of prompt and nonprompt mesons and those from decays of b hadrons, measured from PbPb and pp collisions at the LHC, are reported.
Abstract: The nuclear modification factor [Formula: see text] and the azimuthal anisotropy coefficient [Formula: see text] of prompt and nonprompt (i.e. those from decays of b hadrons) [Formula: see text] mesons, measured from PbPb and pp collisions at [Formula: see text] [Formula: see text] at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta [Formula: see text] [Formula: see text] and rapidity [Formula: see text], extending down to [Formula: see text] [Formula: see text] in the [Formula: see text] range. The [Formula: see text] of prompt [Formula: see text] is found to be nonzero, but with no strong dependence on centrality, rapidity, or [Formula: see text] over the full kinematic range studied. The measured [Formula: see text] of nonprompt [Formula: see text] is consistent with zero. The [Formula: see text] of prompt [Formula: see text] exhibits a suppression that increases from peripheral to central collisions but does not vary strongly as a function of either y or [Formula: see text] in the fiducial range. The nonprompt [Formula: see text] [Formula: see text] shows a suppression which becomes stronger as rapidity or [Formula: see text] increases. The [Formula: see text] and [Formula: see text] of open and hidden charm, and of open charm and beauty, are compared.
99 citations
••
TL;DR: In this paper, an inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1
Abstract: An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb-1 of integrated luminosity. The selected events are analyzed in the 2D razor space of MR, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number of events beyond that predicted by the standard model. Exclusion limits are derived in the CMSSM framework as well as for simplified models. Within the CMSSM parameter space considered, gluino masses up to 800 GeV and squark masses up to 1.35 TeV are excluded at 95% confidence level depending on the model parameters. The direct production of pairs of top or bottom squarks is excluded for masses as high as 400 GeV.
83 citations
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2337 more•Institutions (194)
TL;DR: In this article, the fiducial cross section for the production of Upsilon(1S) pairs, assuming that both mesons decay isotropically, is measured to be 688 +/- 127 (stat) +/- 74 (syst) +/- 28 (B) pb.
Abstract: Pair production of Upsilon(1S) mesons is observed at the LHC in proton-proton collisions at sqrt(s) = 8 TeV by the CMS experiment in a data sample corresponding to an integrated luminosity of 207 inverse-femtobarns Both Upsilon(1S) candidates are fully reconstructed via their decays to mu+ mu- The fiducial acceptance region is defined by an absolute Upsilon(1S) rapidity smaller than 20 The fiducial cross section for the production of Upsilon(1S) pairs, assuming that both mesons decay isotropically, is measured to be 688 +/- 127 (stat) +/- 74 (syst) +/- 28 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of Upsilon(1S) decays to mu+ mu- Assuming instead that the Upsilon(1S) mesons are produced with different polarizations leads to variations in the measured cross section in the range from -38% to +36%
68 citations
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2331 more•Institutions (196)
TL;DR: In this paper, a search is presented for decays beyond the standard model of the 125 GeV Higgs bosons to a pair of light bosons, based on models with extended scalar sectors.
Abstract: A search is presented for decays beyond the standard model of the 125 GeV Higgs bosons to a pair of light bosons, based on models with extended scalar sectors. Light boson masses between 5 and 62.5 GeV are probed in final states containing four τ leptons, two muons and two b quarks, or two muons and two τ leptons. The results are from data in proton-proton collisions corresponding to an integrated luminosity of 19.7 fb−1, accumulated by the CMS experiment at the LHC at a center-of-mass energy of 8 TeV. No evidence for such exotic decays is found in the data. Upper limits are set on the product of the cross section and branching fraction for several signal processes. The results are also compared to predictions of two-Higgs-doublet models, including those with an additional scalar singlet.
66 citations
••
TL;DR: This is the first search for a narrow-width spin-2 resonance at s=13 TeV, and final states, cross section and mass exclusion limits are set for models that predict heavy spin-1 andspin-2 resonances.
Abstract: A search is presented for new massive resonances decaying to WW, WZ or ZZ bosons in lνqq and qqqq final states. Results are based on data corresponding to an integrated luminosity of 2.3-2.7 fb^(−1) recorded in proton-proton collisions at √s=13 TeV with the CMS detector at the LHC. Decays of spin-1 and spin-2 resonances into two vector bosons are sought in the mass range 0.6-4.0 TeV. No significant excess over the standard model background is observed. Combining the results of the lνqq and qqqq final states, cross section and mass exclusion limits are set for models that predict heavy spin-1 and spin-2 resonances. This is the first search for a narrow-width spin-2 resonance at √s=13 TeV.
53 citations
••
TL;DR: Normalized double-differential cross sections for top quark pair production are measured in pp collisions at a centre-of-mass energy of 8 with the CMS experiment at the LHC as mentioned in this paper.
Abstract: Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution.
52 citations
••
Albert M. Sirunyan1, Robin Erbacher2, C. A. Carrillo Montoya3, Wagner Carvalho4 +2279 more•Institutions (149)
TL;DR: 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.
Abstract: 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.
51 citations
••
Albert M. Sirunyan, Robin Erbacher1, C. A. Carrillo Montoya2, Wagner Carvalho3 +2323 more•Institutions (190)
TL;DR: In this article, a search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model process and to search for flavour-changing neutral current interactions.
Abstract: A search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model process and to search for flavour-changing neutral current interactions. The data sample corresponds to an integrated luminosity of 19.7 fb^(−1) recorded by the CMS experiment at the LHC in proton-proton collisions at √s = 8 TeV. Final states with three leptons (electrons or muons) and at least one jet are investigated. An events yield compatible with tZq standard model production is observed, and the corresponding cross section is measured to be σ(pp → tZq → lνbl^+l^−q) = 10_(−7)^(+8) fb with a significance of 2.4 standard deviations. No presence of flavour-changing neutral current production of tZq is observed. Exclusion limits at 95% confidence level on the branching fractions of a top quark decaying to a Z boson and an up or a charm quark are found to be ℬ(t → Zu) < 0.022% and ℬ(t → Zc) < 0.049%.
••
TL;DR: In this article, a search was performed for electroweak production of a vector-like top quark partner T of charge 2/3 in association with a standard model top or bottom quark, using 2.3 inverse femtobarns of proton-proton collision data at sqrt(s) = 13 TeV collected by the CMS experiment at the CERN LHC.
Abstract: A search is performed for electroweak production of a vector-like top quark partner T of charge 2/3 in association with a standard model top or bottom quark, using 2.3 inverse femtobarns of proton-proton collision data at sqrt(s) = 13 TeV collected by the CMS experiment at the CERN LHC. The search targets T quarks decaying to a top quark and a Higgs boson in fully hadronic final states. For a T quark with mass above 1 TeV the daughter top quark and Higgs boson are highly Lorentz-boosted and can each appear as a single hadronic jet. Jet substructure and b tagging techniques are used to identify the top quark and Higgs boson jets, and to suppress the standard model backgrounds. An excess of events is searched for in the T quark candidate mass distribution in the data, which is found to be consistent with the expected backgrounds. Upper limits at 95% confidence level are set on the product of the single T quark production cross sections and the branching fraction B(T to tH), and these vary between 0.31 and 0.93 pb for T quark masses in the range 1000-1800 GeV. This is the first search for single electroweak production of a vector-like T quark in fully hadronic final states.
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2287 more•Institutions (141)
TL;DR: In this article, a measurement of the top quark pair production (t-tbar) cross section in proton-proton collisions at the centre-of-mass energy of 8 TeV is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6 inverse-femtobarns.
Abstract: A measurement of the top quark pair production (t-tbar) cross section in proton-proton collisions at the centre-of-mass energy of 8 TeV is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6 inverse-femtobarns. This analysis is performed in the t-tbar decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured t-tbar cross section is 228.5 +/- 3.8 (stat) +/- 13.7 (syst) +/- 6.0 (lumi) pb. This measurement is compared with an analysis of 7 TeV data, corresponding to an integrated luminosity of 5.0 inverse-femtobarns, to determine the ratio of 8 TeV to 7 TeV cross sections, which is found to be 1.43 +/- 0.04 (stat) +/- 0.07 (syst) +/- 0.05 (lumi). The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2312 more•Institutions (188)
TL;DR: The Belgian Fondation de la Recherche Scienti que, and Fonds voor Wetenschappelijk Onderzoek (FWDO) as discussed by the authors are the main contributors of the Austrian Science Fund.
Abstract: the Austrian
Federal Ministry of Science, Research and Economy and the Austrian Science Fund; the Belgian Fonds de la Recherche Scienti que, and Fonds voor Wetenschappelijk Onderzoek;
the Brazilian Funding Agencies (CNPq, CAPES, FAPERJ, and FAPESP); the Bulgarian
Ministry of Education and Science; CERN; the Chinese Academy of Sciences, Ministry of
Science and Technology, and National Natural Science Foundation of China; the Colombian
Funding Agency (COLCIENCIAS); the Croatian Ministry of Science, Education and
Sport, and the Croatian Science Foundation; the Research Promotion Foundation, Cyprus;
the Secretariat for Higher Education, Science, Technology and Innovation, Ecuador; the
Ministry of Education and Research, Estonian Research Council via IUT23-4 and IUT23-
6 and European Regional Development Fund, Estonia; the Academy of Finland, Finnish
Ministry of Education and Culture, and Helsinki Institute of Physics; the Institut National
de Physique Nucl eaire et de Physique des Particules / CNRS, and Commissariat a l' Energie
Atomique et aux Energies Alternatives / CEA, France; the Bundesministerium f ur Bildung
und Forschung, Deutsche Forschungsgemeinschaft, and Helmholtz-Gemeinschaft Deutscher
Forschungszentren, Germany; the General Secretariat for Research and Technology, Greece;
the National Scienti c Research Foundation, and National Innovation O ce, Hungary; the
Department of Atomic Energy and the Department of Science and Technology, India; the
Institute for Studies in Theoretical Physics and Mathematics, Iran; the Science Foundation,
Ireland; the Istituto Nazionale di Fisica Nucleare, Italy; the Ministry of Science, ICT
and Future Planning, and National Research Foundation (NRF), Republic of Korea; the
Lithuanian Academy of Sciences; the Ministry of Education, and University of Malaya
(Malaysia); the Mexican Funding Agencies (BUAP, CINVESTAV, CONACYT, LNS, SEP,
and UASLP-FAI); the Ministry of Business, Innovation and Employment, New Zealand;
the Pakistan Atomic Energy Commission; the Ministry of Science and Higher Education
and the National Science Centre, Poland; the Funda c~ao para a Ci^encia e a Tecnologia,
Portugal; JINR, Dubna; the Ministry of Education and Science of the Russian Federation,
the Federal Agency of Atomic Energy of the Russian Federation, Russian Academy of
Sciences, and the Russian Foundation for Basic Research; the Ministry of Education, Science
and Technological Development of Serbia; the Secretar a de Estado de Investigaci on,
Desarrollo e Innovaci on and Programa Consolider-Ingenio 2010, Spain; the Swiss Funding
Agencies (ETH Board, ETH Zurich, PSI, SNF, UniZH, Canton Zurich, and SER); the
Ministry of Science and Technology, Taipei; the Thailand Center of Excellence in Physics,
the Institute for the Promotion of Teaching Science and Technology of Thailand, Special
Task Force for Activating Research and the National Science and Technology Development
Agency of Thailand; the Scienti c and Technical Research Council of Turkey, and Turkish
Atomic Energy Authority; the National Academy of Sciences of Ukraine, and State Fund
for Fundamental Researches, Ukraine; the Science and Technology Facilities Council, U.K.;
the US Department of Energy, and the US National Science Foundation.
••
Vardan Khachatryan, Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam1 +2298 more•Institutions (150)
TL;DR: In this paper, an inclusive search is performed for supersymmetry in final states containing jets and an apparent imbalance in transverse momentum, p → T miss, due to the production of unobserved weakly interacting particles in pp collisions at a centre-of-mass energy of 8 TeV.
••
TL;DR: In this paper, the authors acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN;
Abstract: we acknowledge the enduring support for the construction
and operation of the LHC and the CMS detector provided
by the following funding agencies: BMWFW and FWF
(Austria); FNRS and FWO (Belgium); CNPq, CAPES,
FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN;
CAS, MoST, and NSFC (China); COLCIENCIAS
(Colombia); MSES and CSF (Croatia); RPF (Cyprus);
SENESCYT (Ecuador); MoER, ERC IUT, and ERDF
(Estonia); Academy of Finland, MEC, and HIP
(Finland); CEA and CNRS/IN2P3 (France); BMBF,
DFG, and HGF (Germany); GSRT (Greece); OTKA and
NIH (Hungary); DAE and DST (India); IPM (Iran); SFI
(Ireland); INFN (Italy); MSIP and NRF (Republic of
Korea); LAS (Lithuania); MOE and UM (Malaysia);
BUAP, CINVESTAV, CONACYT, LNS, SEP, and
UASLP-FAI (Mexico); MBIE (New Zealand); PAEC
(Pakistan); MSHE and NSC (Poland); FCT (Portugal);
JINR (Dubna); MON, RosAtom, RAS, and RFBR
(Russia); MESTD (Serbia); SEIDI and CPAN (Spain);
Swiss Funding Agencies (Switzerland); MST (Taipei);
ThEPCenter, IPST, STAR, and NSTDA (Thailand);
TUBITAK and TAEK (Turkey); NASU and SFFR
(Ukraine); STFC (United Kingdom); DOE and NSF
(USA). Individuals have received support from the
Marie-Curie program and the European Research
Council and EPLANET (European Union); the Leventis
Foundation; the A. P. Sloan Foundation; the Alexander von
Humboldt Foundation; the Belgian Federal Science Policy
Office; the Fonds pour la Formation a la Recherche dans
l’Industrie et dans l’Agriculture (FRIA-Belgium); the
Agentschap voor Innovatie door Wetenschap en
Technologie (IWT-Belgium); the Ministry of Education,
Youth and Sports (MEYS) of the Czech Republic; the
Council of Science and Industrial Research, India; the
HOMING PLUS program of the Foundation for Polish
Science cofinanced from European Union, Regional
Development Fund, the Mobility Plus program of the
Ministry of Science and Higher Education, the National
Science Center (Poland), Contracts No. Harmonia 2014/14/
M/ST2/00428, No. Opus 2013/11/B/ST2/04202, No. 2014/
13/B/ST2/02543 and No. 2014/15/B/ST2/03998,
No. Sonata-bis 2012/07/E/ST2/01406; the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek
NSRF; the National Priorities Research Program by Qatar
National Research Fund; the Programa Clarin-COFUND
del Principado de Asturias; the Rachadapisek Sompot Fund
for Postdoctoral Fellowship, Chulalongkorn University and
the Chulalongkorn Academic into its 2nd Century Project
Advancement Project (Thailand); the Welch Foundation,
Contract No. C-1845.
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2318 more•Institutions (193)
TL;DR: In this paper, a search for the electroweak production of supersymmetric particles in pp collisions in final states with two τ leptons was conducted and the results were interpreted using simplified models describing the pair production and decays of charginos or τ sleptons.
Abstract: Results are presented from a search for the electroweak production of supersymmetric particles in pp collisions in final states with two τ leptons. The data sample corresponds to an integrated luminosity between 18.1 fb−1 and 19.6 fb−1 depending on the final state of τ lepton decays, at $$ \sqrt{s}=8 $$
TeV, collected by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with the expected standard model backgrounds. The results are interpreted using simplified models describing the pair production and decays of charginos or τ sleptons. For models describing the pair production of the lightest chargino, exclusion regions are obtained in the plane of chargino mass vs. neutralino mass under the following assumptions: the chargino decays into third-generation sleptons, which are taken to be the lightest sleptons, and the sleptons masses lie midway between those of the chargino and the neutralino. Chargino masses below 420 GeV are excluded at a 95% confidence level in the limit of a massless neutralino, and for neutralino masses up to 100 GeV, chargino masses up to 325 GeV are excluded at 95% confidence level. Constraints are also placed on the cross section for pair production of τ sleptons as a function of mass, assuming a massless neutralino.
••
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2320 more•Institutions (193)
TL;DR: In this article, cross sections for the production of a Z boson in association with jets in proton-proton collisions at a centre-of-mass energy of √s=8 TeV are measured using a data sample collected by the CMS experiment at the LHC corresponding to 19.6 fb^(−1).
Abstract: Cross sections for the production of a Z boson in association with jets in proton-proton collisions at a centre-of-mass energy of √s=8 TeV are measured using a data sample collected by the CMS experiment at the LHC corresponding to 19.6 fb^(−1). Differential cross sections are presented as functions of up to three observables that describe the jet kinematics and the jet activity. Correlations between the azimuthal directions and the rapidities of the jets and the Z boson are studied in detail. The predictions of a number of multileg generators with leading or next-to-leading order accuracy are compared with the measurements. The comparison shows the importance of including multi-parton contributions in the matrix elements and the improvement in the predictions when next-to-leading order terms are included.
••
TL;DR: In this article, the pseudorapidity separation (Delta eta) of the particle pair at small relative azimuthal angle (abs(Delta phi) < pi/3) is decomposed into a jet component that dominates the short-range correlations and a component that persists at large Delta eta and may originate from collective behavior of the produced system.
Abstract: Two-particle correlations in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are studied as a function of the pseudorapidity separation (Delta eta) of the particle pair at small relative azimuthal angle (abs(Delta phi)< pi/3). The correlations are decomposed into a jet component that dominates the short-range correlations (abs(Delta eta) < 1), and a component that persists at large Delta eta and may originate from collective behavior of the produced system. The events are classified in terms of the multiplicity of the produced particles. Finite azimuthal anisotropies are observed in high-multiplicity events. The second and third Fourier components of the particle-pair azimuthal correlations, V[2] and V[3], are extracted after subtraction of the jet component. The single-particle anisotropy parameters v[2] and v[3] are normalized by their lab frame mid-rapidity value and are studied as a function of eta[cm]. The normalized v[2] distribution is found to be asymmetric about eta[cm] = 0, with smaller values observed at forward pseudorapidity, corresponding to the direction of the proton beam, while no significant pseudorapidity dependence is observed for the normalized v[3] distribution within the statistical uncertainties.
••
TL;DR: In this paper, a search for a neutral spin-1 heavy resonance decaying to a top quark and a vector-like T quark in the all-hadronic final state is presented.
Abstract: A search is presented for massive spin-1 Z′ resonances decaying to a top quark and a heavy vector-like top quark partner T. The search is based on a 2.6 fb−1 sample of proton-proton collisions at 13 TeV collected with the CMS detector at the LHC. The analysis is optimized for final states in which the T quark decays to a W boson and a bottom quark. The focus is on all-jet final states in which both the W boson and the top quark decay into quarks that evolve into jets. The decay products of the top quark and of the W boson are assumed to be highly Lorentz-boosted and cannot be reconstructed as separate jets, but are instead reconstructed as merged, wide jets. Techniques for the identification of jet substructure and jet flavour are used to distinguish signal from background events. Several models for Z′ bosons decaying to T quarks are excluded at 95% confidence level, with upper limits on the cross section ranging from 0.13 to 10 pb, depending on the chosen hypotheses. This is the first search for a neutral spin-1 heavy resonance decaying to a top quark and a vector-like T quark in the all-hadronic final state.
••
TL;DR: In this article, the mass difference between the top quark and antiquark ( Δ m t = m t − m t ‾ ) that are produced in pp collisions at a center-of-mass energy of 8 TeV, using events with a muon or an electron and at least four jets in the final state.
••
TL;DR: The newly developed DCS system developed for the slice test has been tested with CMS Triple-GEM detectors and the first results obtained in the GEM assembly and quality assurance laboratory are presented.
Abstract: The CMS experiment at LHC will upgrade its forward muon spectrometer by incorporating Triple-GEM detectors. This upgrade referred to as GEM Endcap (GE1/1), consists of adding two back-to-back Triple-GEM detectors in front of the existing Cathode Strip Chambers (CSC) in the innermost ring of the endcap muon spectrometer. Before the full installation of 144 detectors in 2019–2020, CMS will first install ten single chamber prototypes during the early 2017. This pre-installation is referred as the slice test. These ten detectors will be read-out by VFAT2 chips [1]. On-detector there is also a FPGA mezzanine card which sends VFAT2 data optically to the μTCA back-end electronics. The correct and safe operation of the GEM system requires a sophisticated and powerful online Detector Control System, able to monitor and control many heterogeneous hardware devices. The DCS system developed for the slice test has been tested with CMS Triple-GEM detectors in the laboratory. In this paper we describe the newly developed DCS system and present the first results obtained in the GEM assembly and quality assurance laboratory.
01 Apr 2017
••
TL;DR: In this article, the mechanical stability of tracker components during physics operation was monitored with a few micron resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions.
Abstract: The CMS tracker consists of 206 square meters of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from -25 to +25 degrees C. The mechanical stability of tracker components during physics operation was monitored with a few micron resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011-2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30 microns. In addition, temperature variations were found to cause displacements of tracker structures of about 2 microns/degree C, which largely revert to their initial positions when the temperature is restored to its original value.