Speaker
Description
[with a not-yet defined ATLAS speaker]
Search for deviations from the standard model is performed in the
systems of the neutral B mesons. The Bs system is studied in the decay
into J/psi phi. The mixing phase phi_s and the width difference
DeltaGamma_s are determined through the simultaneous study of angular
distributions in the final state and of the decay time, performed
together with flavour tagging at production. The measurement
performed by ATLAS with the full LHC Run-1 sample is discussed and
compared to the previous world average. The width difference
DeltaGamma_d in the Bd system is obtained from the comparison of the
decay time distributions in the flavour specific state J/psi K* and in
the CP eigenstate J/psi KS. The result obtained from the full sample
of data collected by ATLAS at 7 and 8 TeV is the most accurate single
measurement of the width difference currently available.
