LHCb Collaboration (Including: Back, J. J., Craik, Daniel, Dossett, D., Gershon, T. J., Harrison, P. F., Kreps, Michal, Latham, Thomas, Pilar, T., Poluektov, Anton, Reid, Matthew M., Silva Coutinho, R., Whitehead, M. (Mark) and Williams, M. P.). (2013) First evidence for the decay Bºs → μ+μ-. Physical Review Letters, Volume 110 (Number 2). Article number 021801 . doi:10.1103/PhysRevLett.110.021801 ISSN 0031-9007.

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Abstract

A search for the rare decays Bºs → μ+μ- and Bº→μ+μ- is performed with data collected in 2011 and 2012 with the LHCb experiment at the Large Hadron Collider. The data samples comprise 1.1  fb-1 of proton-proton collisions at √s=8  TeV and 1.0  fb-1 at √s=7  TeV. We observe an excess of Bºs → μ+μ- candidates with respect to the background expectation. The probability that the background could produce such an excess or larger is 5.3×10-4 corresponding to a signal significance of 3.5 standard deviations. A maximum-likelihood fit gives a branching fraction of B(Bºs → μ+μ-)=(3.2-1.2+1.5)×10-9, where the statistical uncertainty is 95% of the total uncertainty. This result is in agreement with the standard model expectation. The observed number of Bº→μ+μ- candidates is consistent with the background expectation, giving an upper limit of B(Bº→μ+μ-)<9.4×10-10 at 95% confidence level.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Proton-proton interactions, Nuclear reactions, Nuclear counters, Mathematical physics
Journal or Publication Title:	Physical Review Letters
Publisher:	American Physical Society
ISSN:	0031-9007
Official Date:	January 2013
Dates:	Date Event January 2013 Published
Volume:	Volume 110
Number:	Number 2
Page Range:	Article number 021801
DOI:	10.1103/PhysRevLett.110.021801
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	25 December 2015
Date of first compliant Open Access:	25 December 2015
Funder:	Brazil. Coordenação do Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Financiadora de Estudos e Projetos (Brazil) (FINEP), European Organization for Nuclear Research (CERN), Guo jia zi ran ke xue ji jin wei yuan hui (China) [National Natural Science Foundation of China] (NSFC), Centre national de la recherche scientifique (France) (CNRS), Institut national de physique nucléaire et de physique des particules (IN2P3), Germany. Bundesministerium für Bildung und Forschung (BMBF), Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Max-Planck-Gesellschaft zur Förderung der Wissenschaften [Max Planck Society for the Advancement of Science], Science Foundation Ireland (SFI), Istituto nazionale di fisica nucleare (INFN), Stichting voor Fundamenteel Onderzoek der Materie (FOM) [Foundation for Fundamental Research on Matter], Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Netherlands Organisation for Scientific Research] (NWO), SCSR (Poland), Autoritatea Nationala pentru Cercetare Stiintifica (ANCS), Federalʹnoe agentstvo po atomnoĭ ėnergii (Russia), Russia (Federation). Ministerstvo obrazovanii︠a︡ i nauki [Ministry of Education and Science], Spain. Ministerio de Ciencia e Innovación (MICINN), Galicia (Spain : Region). Xunta, Catalonia (Spain), Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung [Swiss National Science Foundation] (SNSF), Switzerland. Staatssekretariat für Ausbildung und Forschung (SER), Natsionalʹna akademiia nauk Ukraïny (NAS), Science and Technology Facilities Council (Great Britain) (STFC), National Science Foundation (U.S.) (NSF), European Research Council (ERC)

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