698 research outputs found
Measurements of inclusive W and Z cross sections in pp collisions at ps = 7 TeV
40 pĂĄginas, 8 figuras, 5 tablas.-- Open Access: This article is distributed under the terms of the Creative Commons
Attribution Noncommercial License.-- CMS Collaboration: et al.Measurements of inclusive W and Z boson production cross sections in pp
collisions at ps = 7 TeV are presented, based on 2:9 pb1 of data recorded by the CMS
detector at the LHC. The measurements, performed in the electron and muon decay channels,
are combined to give (pp ! WX) B(W ! ` ) = 9:95 0:07 (stat.) 0:28 (syst.)
1:09 (lumi.) nb and (pp ! ZX) B(Z ! `+`) = 0:931 0:026 (stat.) 0:023 (syst.)
0:102 (lumi.) nb, where ` stands for either e or . Theoretical predictions, calculated at
the next-to-next-to-leading order in QCD using recent parton distribution functions, are
in agreement with the measured cross sections. Ratios of cross sections, which incur an
experimental systematic uncertainty of less than 4%, are also reported.This work was supported by the Austrian Federal
Ministry of Science and Research; the Belgium 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; the Research Promotion Foundation, Cyprus;
the Estonian Academy of Sciences and NICPB; the Academy of Finland, Finnish Ministry
of Education, and Helsinki Institute of Physics; the Institut National de Physique Nucléaire
et de Physique des Particules / CNRS, and Commissariat a l'Ănergie Atomique, France;
the Bundesministerium fĂŒr Bildung und Forschung, Deutsche Forschungsgemeinschaft, and
Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germa-ny; the General Secretariat
for Research and Technology, Greece; the National Scienti c Research Foundation, and
National O ce for Research and Technology, Hungary; the Department of Atomic Energy,
and 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 Korean Ministry of Education, Science and Technology and the
World Class University program of NRF, Korea; the Lithuanian Academy of Sciences; the
Mexican Funding Agencies (CINVESTAV, CONACYT, SEP, and UASLP-FAI); the Pakistan
Atomic Energy Commission; the State Commission for Scienti c Research, Poland;
the Fundaçùo para a CiĂȘncia e a Tecnologia, Portugal; JINR (Armenia, Belarus, Georgia,
Ukraine, Uzbekistan); the Ministry of Science and Technologies of the Russian Federation,
and Russian Ministry of Atomic Energy; the Ministry of Science and Technological
Development of Serbia; the Ministerio de Ciencia e InnovaciĂłn, and Programa Consolider-
Ingenio 2010, Spain; the Swiss Funding Agencies (ETH Board, ETH Zurich, PSI, SNF,
UniZH, Canton Zurich, and SER); the National Science Council, Taipei; the Scienti c and
Technical Research Council of Turkey, and Turkish Atomic Energy Authority; the Science
and Technology Facilities Council, U.K.; the US Department of Energy, and the US
National Science Foundation.
Individuals have received support from the Marie-Curie programme and the European
Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Associazione per lo Sviluppo Scienti co e
Tecnologico del Piemonte (Italy); the Belgian Federal Science Policy Office; the Fonds pour
la Formation Ă la Recherche dans l'Industrie et dans l'Ăgriculture (FRIA-Belgium); and
the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium).Peer reviewe
Search for heavy stable charged particles in pp collisions at ?s = 7 TeV
The result of a search at the LHC for heavy stable charged particles produced in pp collisions at s?=7TeV
is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb?1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.We are grateful to Anna Kulesza and Michael KrĂ€mer for providing the theoretical production cross sections and associated uncertainties at next-to-leading order for pair production of eg and Ët1. We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR
(Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST
and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
Prompt and non-prompt J/Ï production in pp collisions at âs =TeV
The production of J/Ï mesons is studied in pp collisions at âs = 7 TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample cor- responding to an integrated luminosity of 314 nbâ1. The J/Ï differential cross section is determined, as a function of the J/Ï transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/Ï ) component. Integrated over J/Ï transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range l y l < 2.4, the measured cross sections, times the dimuon decay branching fraction, are 70.9±2.1(stat.)±3.0(syst.)±7.8(luminosity) nb for prompt J/Ï mesons assuming unpolarized production and 26.0 ± 1.4(stat.) ± 1.6(syst.)±9(luminosity) nb for J/Ï mesons from b-hadron decays.We would like to thank Pierre Artoisenet, Jean- Philippe Lansberg, and Ramona Vogt for providing their theoretical predictions in the prompt production models and Matteo Cacciari for predictions in the FONLL scheme. We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes. This work was supported by the Austrian Federal Ministry of Science and Research; the Belgium Fonds de la Recherche Sci- entifique, and Fonds voor Wetenschappelijk Onderzoek; the Brazil- ian 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; the Research Promotion Foundation, Cyprus; the Estonian Academy of Sciences and NICPB; the Academy of Finland, Finnish Ministry of Education, and Helsinki Institute of Physics; the Institut National de Physique NuclĂ©aire et de Physique des Particules/ CNRS, and Commissariat Ă lâĂnergie Atomique, France; the Bundesministerium fĂŒr Bildung und Forschung, Deutsche Forschungsgemeinschaft, and Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany; the General Secretariat for Research and Technology, Greece; the National Scientific Research Foundation, and National Office for Research and Technology, Hungary; the Department of Atomic Energy, and 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 Korean Ministry of Education, Science and Technology and the World Class University program of NRF, Korea; the Lithuanian Academy of Sciences; the Mexican Funding Agencies (CINVESTAV, CONACYT, SEP, and UASLP-FAI); the Pakistan Atomic Energy Commission; the State Commission for Scientific Research, Poland; the Fundação para a CiĂȘncia e a Tecnologia, Portugal; JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); the Ministry of Science and Technologies of the Russian Federation, and Russian Ministry of Atomic Energy; the Ministry of Science and Technological Development of Serbia; the Ministerio de Ciencia e InnovaciĂłn, and Programa Consolider-Ingenio 2010, Spain; the Swiss Funding Agencies (ETH Board, ETH Zurich, PSI, SNF, UniZH, Canton Zurich, and SER); the National Science Council, Taipei; the Scientific and Technical Research Council of Turkey, and Turkish Atomic Energy Authority; the Science and Technology Facilities Council, UK; the US Department of Energy, and the US National Science Foundation. Individuals have received support from the Marie-Curie IEF program (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Associazione per lo Sviluppo Scientifico e Tecnologico del Piemonte (Italy); the Belgian Federal Science Policy Office; the Fonds pour la Formation Ă la Recherche dans lâĂndustrie et dans lâĂgriculture (FRIA-Belgium); and the Agentschap voor Innovatie doorWetenschap en Technologie (IWT-Belgium)
Search for microscopic black hole signatures at the Large Hadron Collider
A search for microscopic black hole production and decay in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 pb?1. Events with large total transverse energy are analyzed for the presence of multiple high-energy jets, leptons, and photons, typical of a signal expected from a microscopic black hole. Good agreement with the standard model backgrounds, dominated by QCD multijet production, is observed for various final-state multiplicities and model-independent limits on new physics in these final states are set. Using simple semi-classical approximation, limits on the minimum black hole mass are derived as well, in the range 3.5?4.5 TeV. These are the first direct limits on black hole production at a particle accelerator.We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
Search for pair production of second-generation scalar leptoquarks in pp collisions at vs=7TeV
A search for pair production of second-generation scalar leptoquarks in the final state with two muons and two jets is performed using proton-proton collision data at ?s=7??TeV collected by the CMS detector at the LHC. The data sample used corresponds to an integrated luminosity of 34??pb?1. The number of observed events is in good agreement with the predictions from the standard model processes. An upper limit is set on the second-generation leptoquark cross section times ?2 as a function of the leptoquark mass, and leptoquarks with masses below 394 GeV are excluded at a 95% confidence level for ?=1, where ? is the leptoquark branching fraction into a muon and a quark. These limits are the most stringent to date.We extend our thanks to Michael KrÀmer for providing the tools for calculation of the leptoquark theoretical cross section and PDF uncertainty. We wish to congratulate our colleagues in the CERN accelerator departments for the
excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
Search for a heavy gauge boson W in the final state with an electron and large missing transverse energy in pp collisions at ?s = 7 TeV
A search for a heavy gauge boson W' has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse energy imbalance Emiss T , using proton?proton collision data corresponding to an integrated luminosity of 36 pb?1. No excess above standard model expectations is seen in the transverse mass distribution of the electron-Emiss T system. Assuming standard-model-like couplings and decay branching fractions, a W' boson with a mass less than 1.36 TeV/c2 is excluded at 95% confidence level.We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
Measurement of the B+ Production Cross Section in pp Collisions at âs=7ââTeV
15 pĂĄginas, 2 figuras, 1 tabla.-- PACS numbers: 13.85.Ni, 12.38.Bx, 14.40.Nd.-- Creative Commons Attribution 3.0 License.-- CMS Collaboration: et al.Measurements of the total and differential cross sections dÏ/dpTB and dÏ/dyB for B+ mesons produced in pp collisions at âs=7ââTeV are presented. The data correspond to an integrated luminosity of 5.8ââpb-1 collected by the CMS experiment operating at the LHC. The exclusive decay B+âJ/ÏK+, with J/ÏâÎŒ+ÎŒ-, is used to detect B+ mesons and to measure the production cross section as a function of pTB and yB. The total cross section for pTB>5ââGeV and |yB|<2.4 is measured to be 28.1±2.4±2.0±3.1ââÎŒb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement.Acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and FCT (Portugal); JINR (Armenia, Belarus, Georgia,
Ukraine, Uzbekistan); MST and MAE (Russia); MSTD
(Serbia); MICINN and CPAN (Spain); Swiss Funding
Agencies (Switzerland); NSC (Taipei); TUBITAK and
TAEK (Turkey); STFC (United Kingdom); DOE and
NSF (USA). NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF,
DFG, and HGF (Germany); GSRT (Greece); OTKA and
NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and
UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland).Peer reviewe
First measurement of the cross section for top-quark pair production in proton-proton collisions at vs=7 TeV
The first measurement of the cross section for top-quark pair production in pp collisions at the
Large Hadron Collider at center-of-mass energy ?s = 7 TeV has been performed using a data sample
corresponding to an integrated luminosity of 3.1 ± 0.3 pb?1 recorded by the CMS detector. This result
utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse
energy, and two or more jets. Backgrounds from Drell?Yan and non-W/Z boson production are estimated
from data. Eleven events are observed in the data with 2.1 ± 1.0 events expected from background. The
measured cross section is 194 ± 72(stat.) ± 24(syst.) ± 21(lumi.) pb, consistent with next-to-leading order
predictionsWe wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
Measurement of the isolated prompt photons production cross section in pp collisions at â s = 7 TeV
The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy EÎłT in pp collisions at âs=7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9âpbâ1. Photons are required to have a pseudorapidity
|ηγ|21ââGeV, covering the kinematic region 0.006<xT<0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations.We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of
the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from the following: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and
FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES
(Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland);
CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (U.K.); DOE and NSF (U.S.)
Inclusive b-hadron production cross section with muons in pp collisions at sâ=7TeV
A measurement of the b-hadron production cross section in proton-proton collisions at sâ=7TeV is presented. The dataset, corresponding to 85 nbâ1, was recorded with the CMS experiment at the LHC using a low-threshold single-muon trigger. Events are selected by the presence of a muon with transverse momentum pÎŒT>6GeV with respect to the beam direction and pseudorapidity |η ÎŒ| < 2.1. The transverse momentum of the muon with respect to the closest jet discriminates events containing b hadrons from background. The inclusive b-hadron production cross section is presented as a function of muon transverse momentum and pseudorapidity. The measured total cross section in the kinematic acceptance is Ï(pp â b + X â ÎŒ + XâČ) = 1.32 ± 0.01(stat) ± 0.30(syst) ± 0.15(lumi)ÎŒb.We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)
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