Study of the production of Λ0b and B0 hadrons in pp collisions and first measurement of the Λ0b → J/ψpK− branching fraction

The product of the Λ0b (B0) differential production cross-section and the branching fraction of the decay Λ0b → J/ψ pK− (B0 → J/ψ K*(892)0) is measured as a function of the beauty hadron transverse momentum, pT, and rapidity, y. The kinematic region of the measurements is pT < 20 GeV/c and 2.0 < y < 4.5. The measurements use a data sample corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb detector in pp collisions at centre-of-mass energies √s = 7 TeV in 2011 and √s = 8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio, fΛ0b /fd, the branching fraction of the decay Λ0b → J/ψ pK− is measured to be B(Λ0b → J/ψ pK−) = (3.17 ± 0.04 ± 0.07 ± 0.34+0−04528) × 10−4, where the first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay B0 → J/ψ K*(892)0, and the fourth is due to the knowledge of fΛ0b /fd. The sum of the asymmetries in the production and decay between Λ0b and Λ0b is also measured as a function of pT and y. The previously published branching fraction of Λ0b → J/ψ pπ−, relative to that of Λ0b → J/ψ pK−, is updated. The branching fractions of Λ0b → Pc+(→ J/ψ p)K− are determined.