Measurement of time-dependent CP-violating asymmetries and constraints on sin (2β+γ) with partial reconstruction of B→D* π± decays

We present a measurement of the time-dependent CP-violating asymmetries in decays of neutral B mesons to the final states D* π±, using approximately 232×106 BB̄ events recorded by the BABAR experiment at the PEP-II e+e- storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high-momentum π± from the B decay and the low-momentum π from the D* decay are used. We measure the parameters related to 2β+γ to be aD*π=-0. 034±0.014±0.009 and cD*π =-0.019±0.022±0. 013. With some theoretical assumptions, we interpret our results in terms of the lower limits |sin (2β+γ)|>0.62(0.35) at 68% (90%) confidence level.