Measurement of the Branching Fraction and $CP$ Asymmetry in Radiative $D^0 \to V \gamma$ Decays

摘要: We report a measurement of the branching fractions of the radiative decays D0→Vγ, where V=ϕ, K¯¯¯¯¯∗0 or ρ0. This is the first observation of the decay D0→ρ0γ. We measure preliminary branching fractions B(D0→ϕγ)=(2.76±0.20±0.08)×10−5, B(D0→K¯¯¯¯¯∗0γ)=(4.66±0.21±0.18)×10−4 and B(D0→ρ0γ)=(1.77±0.30±0.08)×10−5, where the first uncertainty is statistical and the second systematic. We also present the first measurement of CP asymmetry in these decays. The preliminary values are ACP(D0→ϕγ)=−(0.094±0.066±0.001), ACP(D0→K¯¯¯¯¯∗0γ)=−(0.003±0.020±0.000) and ACP(D0→ρ0γ)=0.056±0.151±0.006. The analysis was conducted using 943 fb−1 of data collected by the Belle detector at the KEKB e+e− collider.