Measurement of the ratio of the production cross sections times branching fractions of Bc± → J/ψπ± and B± → J/ψK± and B(B±c→J/ψπ±π±π∓)/B(B±c→J/ψπ±) in pp collisions at s√=7 TeV

Abstract

The ratio of the production cross sections times branching fractions (σ(B±c)B(B±c→J/ψπ±))/(σ(B±)B(B±→J/ψK±)) is studied in proton-proton collisions at a center-of-mass energy of 7 TeV with the CMS detector at the LHC. The kinematic region investigated requires Bc± and B± mesons with transverse momentum pT > 15 GeV and rapidity |y| < 1.6. The data sample corresponds to an integrated luminosity of 5.1 fb−1. The ratio is determined to be [0.48±0.05(stat)±0.03(syst)±0.05 (τBc)]%. The Bc± → J/ψπ±π±π∓ decay is also observed in the same data sample. Using a model-independent method developed to measure the efficiency given the presence of resonant behaviour in the three-pion system, the ratio of the branching fractions B(B±c→J/ψπ±π±π∓)/B(B±c→J/ψπ±) is measured to be 2.55±0.80(stat)±0.33(syst)+0.04−0.01(τBc), consistent with the previous LHCb result.