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Title: Event activity dependence of Y(nS) production in $$\sqrt{s_{NN}}$$=5.02 TeV pPb and $$\sqrt{s}$$=2.76 TeV pp collisions

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 (yCM) < 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)/, 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. Lastly, 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 0.71more » +/- 0.08 (stat.) +/- 0.09 (syst.) for Y(2S) and Y(3S), respectively.« less
  1. Yerevan Physics Inst. (YerPhI), Yerevan (Armenia). et al.
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 1029-8479; arXiv eprint number arXiv:1312.6300
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2014; Journal Issue: 4; Journal ID: ISSN 1029-8479
Springer Berlin
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
The CMS Collaboration
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS quarkonium; heavy ions; heavy-ion collision