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

Apyan, Aram ; Barbieri, Richard Alexander ; Bauer, Gerry P. ; Busza, Wit ; Cali, Ivan Amos ; Chan, Matthew Hans ; Di Matteo, Leonardo ; Dutta, Valentina ; Gomez-Ceballos, Guillelmo ; Goncharov, Maxim ; Gulhan, Doga Can ; Klute, Markus ; Lai, Yue Shi ; Lee, Yen-Jie ; Levin, Andrew Michael ; Luckey, P. David, Jr. ; Ma, Teng ; Paus, Christoph M. E. ; Ralph, Duncan Kelley ; Roland, Christof E. ; Roland, Gunther M. ; Stephans, George S. F. ; Stockli, Fabian ; Sumorok, Konstanty C. ; Velicanu, Dragos Alexandru ; Veverka, Jan ; Wyslouch, Boleslaw ; Yang, Mingming ; Zanetti, Marco ; Zhukova, Victoria

Elsevier

Others  :  http://dspace.mit.edu/openaccess-disseminate/1721.1/97072

美国|英语

来源: MIT Theses in DSpace@MIT

【 摘 要 】

A measurement of the production cross section ratio σ([subscript χb2](1P))/σ([subscript χb1](1P)) is presented. The [subscript χb1](1P) and [subscript 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 [subscript χb1,2](1P) → ϒ(1S) + γ. The emitted photons are measured through their conversion to e[superscript +]e[superscript −] 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[superscript −1] is used to measure the cross section ratio in a phase-space region defined by the photon pseudorapidity, |η[superscript γ]| < 1.0; the ϒ(1S) rapidity, |y[superscript ϒ]| < 1.5; and the ϒ(1S) transverse momentum, 7 < p[ϒ over T] < 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 [subscript χb] branching fractions.