Doubly-heavy baryon weak decays: Ξbc0→pK− and Ξcc+→Σc++(2520)K−

Doubly-heavy baryons, with two heavy and one light quarks, are expected to exist in QCD and their masses have been predicted in the quark model. However their existence is not well established so far in experiment. In this work, we explore the possibility of searching for Ξbc and Ξcc+ in the W-exchange processes, Ξbc0→pK− and Ξcc+→Σc++(2520)K−. On the basis of perturbative calculations, we estimate the branching ratio of the first decay as BR(Ξbc0→p+K−)≈3.21×Rf2×Rτ×10−7, where Rf (Rτ) are the ratios of the decay constants (lifetimes) of Ξbc0 and Λb0. The branching ratio of Ξcc+→Σc++(2520)K− is related to that of Λc+→Δ++K−, and thereby a conjectured topology analysis leads to the range for the branching ratio as: BR(Ξcc+→Σc++(2520)K−)∈[0.36%,1.80%]. The decay Ξcc+→Σc++(2520)K− would be reconstructed in the Λc+K−π+ final state which is easy to access even at a hadron collider. Based on the two facts that abundant heavy quarks can be produced at a hadron collider like LHC, and the branching ratios of Ξbc0→pK− and Ξcc+→Σc++(2520)K− are sizable, we urge our experimental colleagues to perform a search at LHCb. This will presumably lead to the discovery of the Ξbc and Ξcc+, and precision measurements of the branching ratios in the future are helpful to investigate their decay mechanism.