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

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Karancsi, János and Molnár, József and Pálinkás, József and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2015) Measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P)) in pp collisions at √s = 8 TeV. PHYSICS LETTERS B, 743. pp. 383-402. ISSN 0370-2693

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Abstract

A measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P)) is pre- sented. 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 pseu- dorapidity, |ηγ| < 1.0; the Υ(1S) rapidity, |yΥ| < 1.5; and the Υ(1S) transverse momentum, 7 < pΥ T < 40 GeV. The cross section ratio shows no significant de- pendence 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.

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