Search for the doubly heavy baryon Ξ_bc⁺ decaying to J/ψΞ_c⁺ *

A first search for the Ξ_bc⁺ → J/ψΞ_c⁺ decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb⁻¹ recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of 4.3(2.8) and 4.1(2.4) standard deviations at masses of 6571 and 6694 MeV/c², respectively. Upper limits are set on the Ξ_bc⁺ baryon production cross-section times the branching fraction relative to that of the B⁺_c → J/ψD⁺_s decay at centre-of-mass energies of 8 and 13 TeV, in the Ξ_bc⁺ and in the B⁺_c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20 GeV/c, respectively. Upper limits are presented as a function of the Ξ_bc⁺ mass and lifetime.