Suppression of Upsilon excited states in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV
(2011) Physical Review Letters — Vol. 107, p. 52302 (2011)
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- Abstract
- A comparison of the relative yields of Upsilon resonances in the mu(+) mu(-) decay channel in PbPb and pp collisions at a centre-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 PbPb and pp collisions,(Upsilon(2S+3S)/Upsilon(1S)[PbPb])/(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, has been calculated to be less than 1%.
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CMS, Basegmez, S., Bruno, G., Caudron, J., Ceard, L., Cortina Gil, E., De Favereau De Jeneret, J., Delaere, C., Favart, D., Giammanco, A., Grégoire, G., Hollar, J., Lemaitre, V., Liao, J., Militaru, O., Nuttens, C., Ovyn, S., Pagano, D., Pin, A., et al. (2011). Suppression of Upsilon excited states in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV. Physical Review Letters, 107, 52302. https://doi.org/10.1103/PhysRevLett.107.052302 (Original work published 2011)