A comparison of the relative yields of Upsilon resonances in the mu(+)mu(-) decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Upsilon(2S) and Upsilon(3S) excited states to the Upsilon(1S) ground state in Pb-Pb and pp collisions, [Upsilon(2S + 3S)/Upsilon(1S)](Pb-Pb) /[Upsilon 2S + 3S)/Upsilon(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%. RI Stahl, Achim/E-8846-2011; Mertzimekis, Theodore/A-3287-2008; Hektor, Andi/G-1804-2011; Wulz, Claudia-Elisabeth/H-5657-2011; Chen, Jie/H-6210-2011; Bolton, Tim/A-7951-2012; Yang, Fan/B-2755-2012; Krammer, Manfred/A-6508-2010; Tinoco Mendes, Andre David/D-4314-2011; Petrushanko, Sergey/D-6880-2012; Lokhtin, Igor/D-7004-2012; Kodolova, Olga/D-7158-2012; Perfilov, Maxim/E-1064-2012; Belyaev, Andrey/E-1540-2012; Katkov, Igor/E-2627-2012; Boos, Eduard/D-9748-2012; Snigirev, Alexander/D-8912-2012; Tomei, Thiago/E-7091-2012; Focardi, Ettore/E-7376-2012; Novaes, Sergio/D-3532-2012; Padula, Sandra /G-3560-2012; Flix, Josep/G-5414-2012; Fruhwirth, Rudolf/H-2529-2012; Azzi, Patrizia/H-5404-2012; Torassa, Ezio/I-1788-2012

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%.

Indications of Suppression of Excited Upsilon States in Pb-Pb Collisions at root(NN)-N-s=2.76 TeV

LIGABUE, FRANCO;ROLANDI, LUIGI;
2011

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%.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/2923
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