Measurement of the production cross sections for a Z boson and one or more b jets in pp collisions at root s=7 TeV
Austrian Federal Ministry of Science and Research ; Austrian Science Fund ; Belgian Fonds de la Recherche Scientifique ; Fonds voor Wetenschappelijk Onderzoek ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Bulgarian Ministry of Education and Science ; CERN ; Chinese Academy of Sciences, Ministry of Science and Technology, and National Natural Science Foundation of China ; Colombian Funding Agency (COLCIENCIAS) ; Croatian Ministry of Science, Education and Sport ; Croatian Science Foundation ; Research Promotion Foundation, Cyprus ; Ministry of Education and Research ; European Regional Development Fund, Estonia ; Academy of Finland ; Finnish Ministry of Education and Culture, and Helsinki Institute of Physics ; Institut National de Physique Nucleaire et de Physique des Particules / CNRS ; Commissariat a l'Energie Atomique et aux Energies Alternatives / CEA, France ; Bundesministerium fur Bildung und Forschung ; Deutsche Forschungsgemeinschaft ; Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany ; General Secretariat for Research and Technology, Greece ; National Scientific Research Foundation ; National Innovation Office, Hungary ; Department of Atomic Energy ; Department of Science and Technology, India ; Institute for Studies in Theoretical Physics and Mathematics, Iran ; Science Foundation, Ireland ; Istituto Nazionale di Fisica Nucleare, Italy ; Korean Ministry of Education, Science and Technology ; World Class University program of NRF, Republic of Korea ; Lithuanian Academy of Sciences ; Ministry of Education, and University of Malaya (Malaysia) ; CINVESTAV ; CONACYT ; SEP ; UASLP-FAI ; Ministry of Business, Innovation and Employment, New Zealand ; Pakistan Atomic Energy Commission ; Ministry of Science and Higher Education ; National Science Centre, Poland ; Funda, cao para a Ciencia e a Tecnologia, Portugal ; JINR, Dubna ; Ministry of Education and Science of the Russian Federation ; Federal Agency of Atomic Energy of the Russian Federation ; Russian Academy of Sciences ; Russian Foundation for Basic Research ; Ministry of Education, Science and Technological Development of Serbia ; Secretaria de Estado de Investigacion, Desarrollo e Innovacion and Programa Consolider-Ingenio, Spain ; ETH Board ; ETH Zurich ; PSI ; SNF ; UniZH ; Canton Zurich ; SER ; National Science Council, Taipei ; Thailand Center of Excellence in Physics ; Institute for the Promotion of Teaching Science and Technology of Thailand ; Special Task Force for Activating Research ; National Science and Technology Development Agency of Thailand ; Scientific and Technical Research Council of Turkey ; Turkish Atomic Energy Authority ; Science and Technology Facilities Council, U.K. ; US Department of Energy, and the US National Science Foundation ; Marie-Curie programme ; European Research Council and EPLANET (European Union) ; Leventis Foundation ; A. P. Sloan Foundation ; Alexander von Humboldt Foundation ; Belgian Federal Science Policy Office ; Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium) ; Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium) ; Ministry of Education, Youth and Sports (MEYS) of Czech Republic ; Council of Science and Industrial Research, India ; Compagnia di San Paolo (Torino) ; HOMING PLUS programme of Foundation for Polish Science ; EU ; Regional Development Fund ; Thalis and Aristeia programmes ; EU-ESF ; Greek NSRF ; Ministry of Education and ResearchSF0690030s09 ; The production of a Z boson, decaying into two leptons and produced in association with one or more b jets, is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV. The data were recorded in 2011 with the CMS detector and correspond to an integrated luminosity of 5 fb(-1). The Z(ll) + b-jets cross sections (where ll = mu mu or ee) are measured separately for a Z boson produced with exactly one b jet and with at least two b jets. In addition, a cross section ratio is extracted for a Z boson produced with at least one b jet, relative to a Z boson produced with at least one jet. The measured cross sections are compared to various theoretical predictions, and the data favour the predictions in the five-flavour scheme, where b quarks are assumed massless. The kinematic properties of the reconstructed particles are compared with the predictions from the MadGraph event generator using the pythia parton shower simulation.