Measurement of the Direct CP Asymmetry in b→sγ Decays

We describe a measurement of the direct CP asymmetry between inclusive b→sγ and b̅ →s̅ γ decays. This asymmetry is expected to be less than 0.01 in the standard model, but could be enhanced up to about 0.10 by new physics contributions. We use a sample of 89×106 BB̅ pairs recorded with the BABAR detector at SLAC PEP-II, from which we reconstruct a set of 12 exclusive b→sγ final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of ACP(b→sγ)=0.025±0.050(stat)±0.015(syst), corresponding to an allowed range of -0.06<ACP(b→sγ)<+0.11 at 90% confidence level.