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First evidence for the decay Bs -> mu+ mu-
Aaij R., Barsuk S., Callot O., He J., Jean-Marie B. et al
Physical Review Letters 110 (2013) 021801 - http://hal.in2p3.fr/in2p3-00751272
Physics/High Energy Physics - Experiment
First evidence for the decay Bs -> mu+ mu-
R. Aaij, S. Barsuk1, O. Callot1, J. He1, B. Jean-Marie1, J. Lefrançois1, F. Machefert1, A. Martin Sanchez1, M. Nicol1, P. Robbe1, M.-H. Schune1, B. Viaud1, I. Videau1, E. Ben-Haim2, M. Benayoun2, P. David2, L. Del Buono2, A. Martens2, Z J Ajaltouni ()3, O. Deschamps3, E. Cogneras3, I. El Rifai3, P. Henrard3, M. Hoballah3, M. Jahjah Hussein3, R. Lefèvre3, L. Li Gioi3, S. Monteil3, V. Niess3, P. Perret3, D.A. Roa Romero3, K. Sobczak3, C. Adrover4, E. Aslanides4, J. Cogan4, R. Legac4, O. Leroy4, G. Mancinelli4, E. Maurice4, M. Perrin-Terrin4, M. Sapunov4, J. Serrano4, A. Tsaregorodtsev4, I. De Bonis5, D. Decamp5, Ph. Ghez5, P. Hopchev5, J.-P. Lees5, I.V. Machikhiliyan5, M.-N. Minard5, B. Pietrzyk5, W. Qian5, S. T'Jampens5, V. Tisserand5, E. Tournefier5
1:  LAL - Laboratoire de l'Accélérateur Linéaire
CNRS : UMR8607 – IN2P3 – Université Paris XI - Paris Sud
Centre Scientifique d'Orsay B.P. 34 91898 ORSAY Cedex
2:  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
CNRS : UMR7585 – IN2P3 – Université Pierre et Marie Curie (UPMC) - Paris VI – Université Paris VII - Paris Diderot
Barre 12-22, 1er étage 4 Place Jussieu 75252 Paris Cedex 05
3:  LPC - Laboratoire de Physique Corpusculaire [Clermont-Ferrand]
CNRS : UMR6533 – IN2P3 – Université Blaise Pascal - Clermont-Ferrand II
Campus des Cézeaux 24, avenue des Landais BP 80026 63171 Aubière Cedex
4:  CPPM - Centre de Physique des Particules de Marseille
CNRS : UMR7346 – IN2P3 – Université de la Méditerranée - Aix-Marseille II
163, avenue de Luminy - Case 902 - 13288 Marseille cedex 09
5:  LAPP - Laboratoire d'Annecy le Vieux de Physique des Particules
CNRS : UMR5814 – IN2P3 – Université de Savoie
9 Chemin de Bellevue - BP 110 - 74941 Annecy-le-Vieux CEDEX - France
A search for the rare decays Bs->mu+mu- and B0->mu+mu- is performed using 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 sqrt{s} = 8 TeV and 1.0 fb^-1 at sqrt{s}=7 TeV. We observe an excess of Bs -> mu+ mu- candidates with respect to the background expectation. The probability that the background could produce such an excess or larger is 5.3 x 10^-4 corresponding to a signal significance of 3.5 standard deviations. A maximum-likelihood fit gives a branching fraction of BR(Bs -> mu+ mu-) = (3.2^{+1.5}_{-1.2}) x 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 B0 -> mu+ mu- candidates is consistent with the background expectation, giving an upper limit of BR(B0 -> mu+ mu-) < 9.4 x 10^-10 at 95% confidence level.

Article in peer-reviewed journal
Physical Review Letters (Phys. Rev. Lett.)
Publisher American Physical Society
ISSN 0031-9007 (eISSN : 1079-7114)

CERN-PH-EP-2012-335; LHCb-PAPER-2012-043
3+6 pages, 2 figures, submitted to Phys. Rev. Lett. - See paper for full list of authors
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