Bs\rightarrow J/psi phi decays at ATLAS

The study of the decay B 0 s → J/ψφ is of significant interest to particle physics as it allows the measurement of the B 0 s mixing phase.The B 0 d → J/ψK * 0 channel provides a valuable testing ground for measurements of B 0 s → J/ψφ due to its equivalent topology and similar helicity structure of the final states, with the advantage of higher statistics.An integrated luminosity of 40 pb -1 of ATLAS pp collision data at a center-of-mass energy of 7 TeV are used to reconstruct B 0 d and B 0 s mesons.A total of 2340 ± 80 (stat) B 0 d signal decays are observed after subtracting the background, with a fitted mass of 5279.6 ± 0.9 (stat) MeV.For B 0 s signal 358 ± 22 (stat) decays are observed, with a fitted mass of 5364.0 ± 1.4 (stat) MeV.Within the statistical uncertainties, the fitted masses of both B mesons are consistent with the world average values.