Event activity dependence of Υ(nS) production in √sNN = 5.02 TeV pPb and √s = 2.76 TeV pp collisions
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Chatrchyan-2014-Event activity depen.pdf
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Author(s)
Busza, Wit
Cali, Ivan Amos
Chan, M.
Di Matteo, Leonardo
Dutta, Valentina
Gomez-Ceballos, Guillelmo
Goncharov, Maxim
Gulhan, Doga Can
Klute, Markus
Lai, Yue Shi
Date Issued
April 2014
Journal
Journal of High Energy Physics
Publisher
Springer-Verlag/International School for Advanced Studies (SISSA)
Citation
Chatrchyan, S., V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam, T. Bergauer, M. Dragicevic, et al. “Event activity dependence of Υ(nS) production in √sNN = 5.02 TeV pPb and √s = 2.76 TeV pp collisions.” J. High Energ. Phys. 2014, no. 4 (April 2014).
Version
Final published version
Abstract
The production of Y (1S), Y (2S), and Y (3S) is investigated in pPb and pp collisions at centre-of-mass energies per nucleon pair of 5.02 TeV and 2.76 TeV, respectively. The datasets correspond to integrated luminosities of about 31 nb−1 (pPb) and 5.4 pb−1 (pp), collected in 2013 by the CMS experiment at the LHC. Upsilons that decay into muons are reconstructed within the rapidity interval |y CM| < 1.93 in the nucleon-nucleon centre-of-mass frame. Their production is studied as a function of two measures of event activity, namely the charged-particle multiplicity measured in the pseudorapidity interval |η| < 2.4, and the sum of transverse energy deposited at forward pseudorapidity, 4.0 < |η| < 5.2. The Y cross sections normalized by their event activity integrated values, Y (nS)/〈 Y (nS)〉, are found to rise with both measures of the event activity in pp and pPb. In both collision systems, the ratios of the excited to the ground state cross sections, Y (nS)/ Y (1S), are found to decrease with the charged-particle multiplicity, while as a function of the transverse energy the variation is less pronounced. The event activity integrated double ratios, [ Y (nS)/ Y (1S)]pPb /[ Y (nS)/ Y (1S)]pp, are also measured and found to be 0.83 ± 0.05 (stat.) ± 0.05 (syst.) and 0.71 ± 0.08 (stat.) ± 0.09 (syst.) for Y (2S) and Y (3S), respectively.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
http://dx.doi.org/10.1007/jhep04(2014)103
