Search for the doubly heavy baryon ${\Xi }_{bc}^{+}$ decaying to $J\mathrm{/}\psi {\Xi }_c^{+}$

A first search for the ${\Xi }_{bc}^{+}\to J\mathrm{/}\psi {\Xi }_c^{+}$ decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of $9{\mathrm{f}\mathrm{b}}^{-1}$ recorded at centre-of-mass energies of 7, 8, and $13\mathrm{,Te\kern -0.1em V}$\mathrm{.}Twopeakingstructuresareseenwithalocal(global)significanceof$4.3,(2.8)$and$4.1,(2.4)$standarddeviationsatmassesof$6571,$\mathrm{M}\mathrm{e}\mathrm{V}\text{\hspace{0.17em}⁣}\mathrm{/}$c^2$and$6694,\mathrm{Me\kern -0.1em V!/}c^2$,respectively\mathrm{.}Upperlimitsaresetonthe$\it{\Xi}_{bc}^{+}$ baryon production cross-section times the branching fraction relative to that of the $B_c^{+}\to J\mathrm{/}\psi D_s^{+}$ decay at centre-of-mass energies of 8 and $13\mathrm{T}\mathrm{e}\mathrm{V}$, in the ${\Xi }_{bc}^{+}$ and in the $B_c^{+}$ rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to $20\mathrm{G}\mathrm{e}\mathrm{V}\text{\hspace{0.17em}⁣}\mathrm{/}c$, respectively. Upper limits are presented as a function of the ${\Xi }_{bc}^{+}$ mass and lifetime.