Study of CP asymmetry in B0-B0bar mixing with inclusive dilepton events

Abstract

We present a measurement of the asymmetry $A_{CP}$ between same-sign inclusive dilepton samples $\ell^+ \ell^+$ and $\ell^- \ell^-$ ($\ell= e, \mu$) from semileptonic B decays in Y(4S) --> BBbar events, using the complete data set recorded by the BABAR experiment near the Y(4S) resonance, corresponding to 471 million BBbar pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B0bar --> B0) and P(B0 --> B0bar), and therefore probes CP and T violation. The result, $A_{CP} = (-3.9 \pm 3.5 (stat) \pm 1.9 (syst)) \times 10^{-3}$, is consistent with the Standard Model expectation.