Journal article

Measurement of the Direct CP Asymmetry in over-bar & RARR; gamma; Decays with a Lepton Tag

Pesantez, L.; Urquijo, P.; Dingfelder, J.; Abdesselam, A.; Adachi, I.; Adamczyk, K.; Aihara, H.; Al Said, S.; Arinstein, K.; Asner, D. M.

Belle Collaboration

We report the measurement of the direct CP asymmetry in the radiative (B) over bar -> Xs+d gamma decay using a data sample of (772 +/- 11) x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The CP asymmetry is measured as a function of the photon energy threshold. For E-gamma* >= 2.1 GeV, where E-gamma* is the photon energy in the center-of-mass frame, we obtain A(CP) ((B) over bar -> Xs+d gamma) = (2.2 +/- 3.9 +/- 0.9)%, consistent with the standard model prediction.


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