Observation of D0 →ρ0γ and Search for CP Violation in Radiative Charm Decays

Abstract

We report the first observation of the radiative charm decay D0→ρ0γ and the first search for CP violation in decays D0→ρ0γ, φγ, and K̄∗0(892)γ, using a data sample of 943 fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fraction is measured to be B(D0→ρ0γ)=(1.77±0.30±0.07)×10-5, where the first uncertainty is statistical and the second is systematic. The obtained CP asymmetries ACP(D0→ρ0γ)=+0.056±0.152±0.006, ACP(D0→φγ)=-0.094±0.066±0.001, and ACP(D0→K̄∗0γ)=-0.003±0.020±0.000 are consistent with no CP violation. We also present an improved measurement of the branching fractions B(D0→φγ)=(2.76±0.19±0.10)×10-5 and B(D0→K̄∗0γ)=(4.66±0.21±0.21)×10-4.