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


Chatrchyan S., Khachatryan V., Sirunyan A. M. , Tumasyan A., Adam W., Bergauer T., ...More

PHYSICAL REVIEW LETTERS, vol.107, no.5, 2011 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 107 Issue: 5
  • Publication Date: 2011
  • Doi Number: 10.1103/physrevlett.107.052302
  • Journal Name: PHYSICAL REVIEW LETTERS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Middle East Technical University Affiliated: Yes

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%.