Abstract
We measure the direct C P violation asymmetry, A C P , in B → X s γ and the isospin difference of the asymmetry, Δ A C P , using 429 fb − 1 of data collected at Υ ( 4 S ) resonance with the BABAR detector at the PEP-II asymmetric-energy e + e − storage rings operating at the SLAC National Accelerator Laboratory. B mesons are reconstructed from ten charged B final states and six neutral B final states. We find A C P = + ( 1.7 ± 1.9 ± 1.0 ) % , which is in agreement with the Standard Model prediction and provides an improvement on the world average. Moreover, we report the first measurement of the difference between A C P for charged and neutral decay modes, Δ A C P = + ( 5.0 ± 3.9 ± 1.5 ) % . Using the value of Δ A C P , we also provide 68% and 90% confidence intervals on the imaginary part of the ratio of the Wilson coefficients corresponding to the chromomagnetic dipole and the electromagnetic dipole transitions.