ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2011, vol. 84, p. -
First observation of radiative B0→·K0γ decays and measurements of their time-dependent CP violation
We report the first observation of the radiative decay B0→· K0γ using a data sample of 772×106 BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal of 37±8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is B(B0→·K0γ)= (2.74±0.60±0.32)×10-6, where the uncertainties are statistical and systematic, respectively. We also report the first measurements of time-dependent CP-violation parameters: S ·KS0γ=+0.74-1.05+0.72(stat)-0.24+0.10(syst) and A ·KS0γ=+0.35±0.58(stat)-0.10+0.23(syst). Furthermore, we measure B(B+→·K+γ)=(2. 48±0.30±0.24)×10-6, ACP=-0. 03±0.11±0.08, and find that the signal is concentrated in the M·K mass region near threshold. © 2011 American Physical Society.