Lifetimes of Doubly Charmed Baryons
Hai-Yang Cheng, Yan-Liang Shi 2018 arXiv 1809.08102The 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 ∼5.2×10−13s∼5.2×10−13s to ∼3.0×10−13s∼3.0×10−13s. The Ξ+ccΞcc+ baryon has the shortest lifetime of order 0.45×10−13s0.45×10−13s 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 (0.75∼1.80)×10−13s(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.