Measurement of the production cross section ratio σ χb2(1P))/ σ (χb1(1P)) in pp collisions at √s=8TeV

Abstract

A measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P)) is presented. The χb1(1P) and χb2(1P) bottomonium states, promptly produced in pp collisions at vs=8TeV, are detected by the CMS experiment at the CERN LHC through their radiative decays χb1,2(1P)→Υ(1S)+γ. The emitted photons are measured through their conversion to e+e-pairs, whose reconstruction allows the two states to be resolved. The Υ(1S) is measured through its decay to two muons. An event sample corresponding to an integrated luminosity of 20.7fb-1is used to measure the cross section ratio in a phase-space region defined by the photon pseudorapidity, ,|ηγ|<1.0;theΥ(1S) rapidity,|yΥ|<1.5;and the Υ(1S) transverse momentum,7<pΥT<40 GeV. The cross section ratio shows no significant dependence on the Υ(1S) transverse momentum, with a measured average value of 0.85 ±0.07 (stat+syst) ±0.08 (BF), where the first uncertainty is the combination of the experimental statistical and systematic uncertainties and the second is from the uncertainty in the ratio of the χb branching fractions.