Study of the Production of Λ0b and anti-B0 Hadrons in pp Collisions and First Measurement of the Λ0b → J/ψ p K− Branching Fraction

The product of the Λ0b (anti-B0) differential production cross-section and the branching fraction of the decay Λ0b → J/ψ p K− (anti-B0 → J/ψ anti-K∗(892)0) is measured as a function of the beauty hadron transverse momentum, p_T, and rapidity, y. The kinematic region of the measurements is p_T < 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, f_Λ0b/f_d, the branching fraction of the decay Λ0b → J/ψ p K− is measured to be B(Λ0b → J/ψ p K−) = (3.17 ± 0.04 ± 0.07 ± 0.34{−0.28}{+0.45}) × 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 anti-B0 → J/ψ K∗(892)0, and the fourth is due to the knowledge of f_Λ0b/f_d. The sum of the asymmetries in the production and decay between Λ0b and anti-Λ0b is also measured as a function of p_T and y. The previously published branching fraction of Λ0b → J/ψ p π−, relative to that of Λ0b → J/ψ p K−, is updated. The branching fractions of Λ0b → P+c (→ J/ψ p) K− are determined.