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

Abstract

The production of χb 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 χb 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 χb1(1P) and χb2(1P) mesons is measured as a function of the Υ(1S) transverse momentum in the χb rapidity range 2.0 < y < 4.5. A precise measurement of the χb(3P) mass is also performed. Assuming a mass splitting between the χb1(3P) and the χb2(3P) states of 10.5 MeV/c2 , the measured mass of the χb1(3P) meson is m(χb1(3P)) = 10515.7 +2.2 −3.9 (stat)+1.5 −2.1 (syst) MeV/c2 .