Lifetimes of Doubly Charmed Baryons

Hai-Yang Cheng, Yan-Liang Shi 2018  arXiv 1809.08102 

The lifetimes of doubly charmed hadrons are analyzed within the framework of the heavy quark expansion (HQE). Lifetime differences arise from spectator effects such as WW-exchange and Pauli interference. The Ξ++ccΞcc++ baryon is longest-lived in the doubly charmed baryon system owing to the destructive Pauli interference absent in the Ξ+ccΞcc+ and Ω+ccΩcc+. In the presence of dimension-7 contributions, its lifetime is reduced from 5.2×1013s∼5.2×10−13s to 3.0×1013s∼3.0×10−13s. The Ξ+ccΞcc+ baryon has the shortest lifetime of order 0.45×1013s0.45×10−13s due to a large contribution from the WW-exchange box diagram. It is difficult to make a precise quantitative statement on the lifetime of Ω+ccΩcc+. Contrary to ΞccΞcc baryons, τ(Ω+cc)τ(Ωcc+) becomes longer in the presence of dimension-7 effects and the Pauli interference Γint+Γ+int even becomes negative. This implies that the subleading corrections are too large to justify the validity of the HQE. Demanding the rate Γint+Γ+int to be positive for a sensible HQE, we conjecture that the Ω0cΩc0 lifetime lies in the range of (0.751.80)×1013s(0.75∼1.80)×10−13s. The lifetime hierarchy pattern is τ(Ξ++cc)>τ(Ω+cc)>τ(Ξ+cc)τ(Ξcc++)>τ(Ωcc+)>τ(Ξcc+) and the lifetime ratio τ(Ξ++cc)/τ(Ξ+cc)τ(Ξcc++)/τ(Ξcc+) is predicted to be of order 6.7.