Measurement of the Time-Dependent CP Asymmetries in B0 → K0Sρ0γ Decays

We report the first measurement of time-dependent CP asymmetry in B-0 -> K-S(0)rho(0)gamma decays based on 657 x 10(6) B (B) over bar B pairs collected with the Belle detector at the KEKB asymmetric-energy collider. We measure the CP-violating parameter S-KS0 rho 0 gamma = 0.11 +/- 0.33(stat)(-0.09)(+0.05)(syst) from a signal of 212 +/- 17 events. We also obtain the effective direct CP-violating parameter A(eff) = 0.05 +/- 0.18(stat) +/- 0.06(syst) for m(KS0 pi+pi-) < 1.8 GeV/c(2) and 0.6 GeV= c(2) < m(pi+pi-) < 0.9 GeV/c(2).