Time-dependent CP violation in B decays at Belle

Abstract

Using the full data sample collected with the Belle detector at the KEKB asymmetric-energye + e collider, we present three recent measurements of time-dependent CP violation in B decays, and a measurement of branching fraction of the B 0 ! r 0 r 0 decay. We studied B! wK decays and measured the values of CP violation parameters in B 0 ! wK 0 S to be A wK 0 S = 0:36 0:19(stat) 0:05(syst) and S wK0 = +0:91 0:32(stat) 0:05(syst), which gives the first evidence of CP violation in this decay. In addition, we measured the direct CP violation in B + ! wK + to be ACP(B + !wK + ) = 0:03 0:04(stat) 0:01(syst), and two branching fractions B(B 0 !wK 0 ) = (4:5 0:4(stat) 0:3(syst)) 10 6 and B(B + ! wK + ) = (6:8 0:4(stat) 0:4(syst)) 10 6 (preliminary). From the measurement of CP violation parameters in the B 0 ! h 0 K 0 decay we obtain Sh0K0 = 0:68 0:07(stat) 0:03(syst) and Ah0K0 = +0:03 0:05(stat) 0:03(syst) (preliminary), which are the world’s most precise values to date. Measuring CP violating parameters in the B 0 ! p + p decay gives Ap+p = +0:33 0:06(stat) 0:03(syst) and Sp+p = 0:64 0:08(stat) 0:03(syst). This result is used in an isospin analysis to constrain the f2 angle of the unitarity triangle, with which we rule out the region 23:8 < f2 < 66:8 at the 1s confidence level. The measured branching fraction of the B 0 ! r 0 r 0 decay is B(B 0 ! r 0 r 0 ) = (1:02 0:30(stat) 0:15(syst)) 10 6 , with the fraction of longitudially polarized r 0 mesons being fL = 0:21 +0:18 0:22 0:13. From the same measurement we obtain also the first evidence of the B 0 ! f0r 0 decay, by measuring B(B 0 ! f0r 0 ) B(f0! p + p ) = (0:86 0:27(stat) 0:14(syst)) 10 6 . Using this result in an isospin analysis we obtain f2 = (91:0 7:2) .