CMS-BPH-13-005

CMS-BPH-13-005 ; CERN-PH-EP-2014-217
Measurement of the production cross section ratio $\sigma(\chi_{b2}(1\mathrm{P}))/ \sigma(\chi_{b1}(1\mathrm{P}))$ in pp collisions at $\sqrt{s}$ = 8 TeV
CMS Collaboration
19 September 2014
Phys. Lett. B 743 (2015) 383
Abstract: A measurement of the production cross section ratio $\sigma(\chi_{b2}(1\mathrm{P}))/ \sigma(\chi_{b1}(1\mathrm{P}))$ is presented. The $\chi_{b1}(1\mathrm{P})$ and $\chi_{b2}(1\mathrm{P})$ bottomonium states, promptly produced in pp collisions at $\sqrt{s}$ = 8 TeV, are detected by the CMS experiment at the CERN LHC through their radiative decays $\chi_{b1,2}(1\mathrm{P}) \rightarrow \Upsilon(1\mathrm{S}) + \gamma$ . The emitted photons are measured through their conversion to e $^+$ e $^-$ pairs, whose reconstruction allows the two states to be resolved. The $\Upsilon(1\mathrm{S})$ 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, \| $\eta^\gamma$ \| < 1.0; the $\Upsilon(1\mathrm{S})$ rapidity, \| $y^\Upsilon$ \| < 1.5; and the $\Upsilon(1\mathrm{S})$ transverse momentum, 7 < $p_{\mathrm{T}}^\Upsilon$ < 40 GeV. The cross section ratio shows no significant dependence on the $\Upsilon(1\mathrm{S})$ transverse momentum, with a measured average value of 0.85 $\pm$ 0.07 (stat+syst) $\pm$ 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 $\chi_{b}$ branching fractions.
Links: e-print arXiv:1409.5761 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; Public twiki page ; CADI line (restricted) ;

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