Lifetimes of doubly heavy baryons Bbb and Bbc

Cheng, Hai-Yang (Institute of Physics, Academia Sinica, Taipei, Taiwan 115, Republic of China) ; Xu, Fanrong (Department of Physics, Jinan University, Guangzhou 510632, People’s Republic of China)

16 April 2019

Abstract: Lifetimes of the doubly heavy baryons Bbb and Bbc are analyzed within the framework of the heavy quark expansion (HQE). Lifetime differences arise from the spectator effects such as W-exchange and Pauli interference. For doubly bottom baryons, the lifetime pattern is τ(Ωbb)τ(Ξbb)>τ(Ξbb0). The Ξbb0 baryon is shortest-lived owing to the W-exchange contribution, while Ξbb and Ωbb have similar lifetimes as they both receive contributions from destructive Pauli interference. We find the lifetime ratio τ(Ξbb)/τ(Ξbb0)=1.26. The large W-exchange contribution to Ξbc0 through the subprocess cduscd and the sizable destructive Pauli interference contribution to Ξbc+ imply a substantial lifetime difference between Ξbc+ and Ξbc0. In the presence of subleading 1/mc and 1/mb corrections to the spectator effects, we find that τ(Ωbc0) becomes longest-lived. This is because Γ+int and Γsemi for Ωbc0 are subject to large cancellation between dimension-6 and -7 operators. This implies that the subleading corrections are too large to justify the validity of the HQE. Demanding that Γint+cs(Ωbc0), ΓintSL,cs(Ωbc0) be positive and Γintcu(Ξbc+) be negative, we conjecture that 1.68×1013s<τ(Ωbc0)<3.70×1013 s, 4.09×1013s<τ(Ξbc+)<6.07×1013 s, and 0.93×1013s<τ(Ξbc0)<1.18×1013 s. Hence, the lifetime hierarchy of Bbc baryons is expected to be τ(Ξbc+)>τ(Ωbc0)>τ(Ξbc0).

Published in: Physical Review D 99 (2019)
Published by: APS
DOI: 10.1103/PhysRevD.99.073006
License: CC-BY-4.0

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