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 √s=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; the ϒ(1S)rapidity, |yϒ| <1.5; and the ϒ(1S)transverse momentum, 7 <pϒT<40GeV. 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 χbbranching fractions.