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%.
Indications of Suppression of Excited Upsilon States in Pb-Pb Collisions at root(s)NN=2.76 TeV
P. Meridiani;AMAPANE, Nicola Carlo;ARGIRO', Stefano;BOTTA, CRISTINA;CASTELLO, Roberto;COSTA, Marco;MIGLIORE, Ernesto;MONACO, Vincenzo;MUSICH, MARCO;OBERTINO, Maria Margherita;PELLICCIONI, Mario;ROMERO, Alessandra;SACCHI, Roberto;SOLA, VALENTINA;SOLANO, Ada Maria;BELLAN, Riccardo;COVARELLI, Roberto;
2011-01-01
Abstract
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%.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.