Measurement of the production cross section ratio $\sigma$(Xb2(1P)) / $\sigma$(Xb1(1P) in pp collisions at $\sqrt s $ = 8 TeV

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=8 TeV , 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 20.7 fb−1 is used to measure the cross section ratio in a phase-space region defined by the photon pseudorapidity, |ηγ|