Non-spectator Contributions to Lifetime of ∧b
Non-spectator Contributions to Lifetime of Λb作者机构:InstituteofTheoreticalPhysicsAcademiaSinicaP.O.Box2735Beijing100080China DepartmentofPhysicsNankaiUniversityTianjin300071China
出 版 物:《Communications in Theoretical Physics》 (理论物理通讯(英文版))
年 卷 期:2004年第42卷第5X期
页 面:723-734页
核心收录:
学科分类:07[理学] 070202[理学-粒子物理与原子核物理] 0702[理学-物理学]
基 金:国家自然科学基金
摘 要:In this work, we study the contributions of non-spectator effects to the lifetimes of Λb and B-mesons comparatively. Based on the well-established theoretical framework about the effective weak Lagrangian, we derive the formulation of the non-spectator effects at the quark level. Especially, for Λb we have considered two pictures: the three-valence-quark picture and the quark-diquark picture. In the two pictures, the interference contributions to the total width are different, in this work, we investigate the interference effects in detail. As a preliminary estimate on the lifetimes, we evaluate the hadronic matrix elements appearing in the final formulas of the lifetimes by means of a simple phenomenological model for both pictures. Our results show that the contributions of the non-spectator effects can reduce the ratio of lifetime of Λb to that of B-mesons by 5 ~ 7%. It is noted that in the quark-diquark picture the ratio can be further reduced if excited states of the diquark system are taken into account. We conclude that the measured ratio τ(Λb)/τ(B0)(≈)0.79 [The Data Group, Phys. Rev. D66 (2002) 010001] can be partly understood by the non-spectator effects, although the problem on the discrepancy between theoretical prediction and experimental measurement is not fully solved.