Measurement of the χ b (3P) mass and of the relative rate of χ b1(1P) and χ b2(1P) production

Abstract

The production of χ b 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 8 TeV and corresponding to an integrated luminosity of 3.0 fb−1. The χ b mesons are identified through their decays to ϒ(1S)γ and ϒ(2S)γ using photons that converted to e + e − pairs in the detector. The relative prompt production rate of χ b1(1P) and χ b2(1P) mesons is measured as a function of the ϒ(1S) transverse momentum in the χ b rapidity range 2.0 < y <4.5. A precise measurement of the χ b (3P) mass is also performed. Assuming a mass splitting between the χ b1(3P) and the χ b2(3P) states of 10.5 MeV/c2, the measured mass of the χ b1(3P) meson is m(χb1(3P))=10515.7+2.2−3.9(stat)+1.5−2.1(syst)MeV/c2.