Indications of suppression of excited? States in Pb-Pb collisions at sNN2.76 TeV
Indications of suppression of excited? States in Pb-Pb collisions at sNN2.76 TeV
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Date
2011-07-28
Authors
Chatrchyan, S.
Khachatryan, V.
Sirunyan, A. M.
Tumasyan, A.
Adam, W.
Bergauer, T.
Dragicevic, M.
Erö, J.
Fabjan, C.
Friedl, M.
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Abstract
A comparison of the relative yields of Υ resonances in the μ+μ- decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4GeV/c and pseudorapidity below 2.4, the double ratio of the Υ(2S) and Υ(3S) excited states to the Υ(1S) ground state in Pb-Pb and pp collisions, [Υ(2S+3S)/Υ(1S)]Pb-Pb/[Υ(2S+3S)/Υ(1S) ]pp, is found to be 0.31-0.15+0.19(stat)±0.03(syst). The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%. © 2011 American Physical Society.
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Physical Review Letters. v.107(5)