分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: We present a measurement of the branching fraction and the longitudinal polarization fraction of B0→ρ+ρ− decays, as well as the time-dependent CP violating parameters in decays into longitudinally polarized ρ+ρ− pairs with Belle's final data set of 772×106 BB¯ pairs, at the Υ(4S) resonance, collected at the asymmetric-energy e+e− collider KEKB. We obtain B(B0→ρ+ρ−)=(28.3±1.5(stat)±1.5(syst))×10−6, fL=0.988±0.012(stat)±0.023(syst), ACP=0.00±0.10(stat)±0.06(syst), SCP=−0.13±0.15(stat)±0.05(syst). We perform an isospin analysis to constrain the CKM angle ϕ2 and obtain two solutions with ϕ2=(93.7±10.6)∘, being most compatible with other Standard-Model based fits to the data.