Measurement of CP violation in B0→D*-π+ and B0→D-π+ decays

We report measurements of time-dependent decay rates for B0→D(*)-π+ decays and extraction of CP violation parameters that depend on 3. Using fully reconstructed D(*)π events and partially reconstructed D*π events from a data sample that contains 386×106 BB̄ pairs that was collected near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric energy e+e- collider, we obtain the CP violation parameters S+(D(*)π) and S-(D(*)π). We obtain S+(D*π)=0.049±0.020(stat)±0.011(sys), S-(D*π)=0.031±0.019(stat)±0.011(sys), and S+(Dπ)=0.031±0.030(stat)±0.012(sys), S-(Dπ)=0.068±0. 029(stat)±0.012(sys). These results are an indication of CP violation in B0→D*-π+ and B0→D-π+ decays at the 2.5σ and 2.2σ levels, respectively. If we use the values of RD(*)π that are derived using assumptions of factorization and SU(3) symmetry, branching fraction measurements for the B→Ds(*)π modes, and lattice QCD calculations, we can restrict the allowed region of |sin (2 1+ 3)| to be above 0.44 and 0.52 at 68% confidence level from the D*π and Dπ modes, respectively.