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Time-dependent angular analysis of the decay Bs -> J/psi phi and extraction of Delta Gamma_s and the CP-violating weak phase phi_s by ATLAS

Research output: Contribution to journalJournal article


Article number72
Journal publication date12/2012
JournalJournal of High Energy Physics
Journal number12
Number of pages42
Early online date2/08/12
Original languageEnglish


A measurement of Bs J/psi phi decay parameters, including the CP-violating weak phase phi_s and the decay width difference Delta Gamma_s is reported, using 4.9 fb-1 of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre- of-mass energy sqrt(s) = 7 TeV. The mean decay width Gamma_s and the transversity amplitudes |A0(0)|^2 and |A||(0)|^2 are also measured. The values reported for these parameters are: phi_s = 0.22 \pm 0.41 (stat.) \pm 0.10 (syst.) rad Delta Gamma_s = 0.053 \pm 0.021 (stat.) \pm 0.010 (syst.) ps-1 Gamma_s = 0.677 \pm 0.007 (stat.) \pm 0.004 (syst.) ps-1 |A0(0)|^2 = 0.528 \pm 0.006 (stat.) \pm 0.009 (syst.) |A||(0)|^2 = 0.220 \pm 0.008 (stat.) \pm 0.007 (syst.) where the values quoted for phi_s and Delta Gamma_s correspond to the solution compatible with the external measurements to which the strong phase delta perpendicular is constrained and where Delta Gamma_s is constrained to be positive. The fraction of S-wave KK or f0 contamination through the decays Bs -> J/psi K+K-(f0) is measured as well and is found to be consistent with zero. Results for phi_s and Delta Gamma_s are also presented as 68%, 90% and 95% likelihood contours, which show agreement with Standard Model expectations.

Bibliographic note

This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. 18 pages plus author list (40 pages total), 5 figures, 4 tables, submitted to Journal of High Energy Physics. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2011-05/