Measurement of the xb(3p) mass and of the relative rate of xb1(1p) and xb2(1p) production

Abstract

The production of Xb mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of √s = 7 and 8TeV and corresponding to an integrated luminosity of 3.0 fb−1. The Xb mesons are identified through their decays to γ(1S) and γ(2S)γ using photons that converted to e+e−pairs in the detector. The relative prompt production rate of Xb1(1P) and Xb2(1P) mesons is measured as a function of the X(1S) transverse momentum in the Xb rapidity range 2.0 < y < 4.5. A precise measurement of the Xb(3P) mass is also performed. Assuming a mass splitting between the Xb1(3P) and the Xb2(3P) states of 10.5 MeV/c2, the measured mass of the Xb1(3P) meson is m(Xb1(3P)) = 10515.7+2.2−3.9(stat)+1.5−2.1(syst)MeV/c2.