Suppression of Excited gamma States Relative to the Ground State in Pb-Pb Collisions at root s(NN)=5.02 TeV

Abstract

The relative yields of Υ mesons produced in p p and Pb-Pb collisions at √ s NN = 5.02 TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ratios are formed by comparing the yields of the excited states, Υ ( 2 S ) and Υ ( 3 S ) , to the ground state, Υ ( 1 S ) , in both Pb-Pb and p p collisions at the same center-of-mass energy. The double ratios, [ Υ ( nS ) / Υ ( 1 S ) ] Pb − Pb / [ Υ ( nS ) / Υ ( 1 S ) ] p p , are measured to be 0.308 ± 0.055 ( stat ) ± 0.019 ( syst ) for the Υ ( 2 S ) and less than 0.26 at 95% confidence level for the Υ ( 3 S ) . No significant Υ ( 3 S ) signal is found in the Pb-Pb data. The double ratios are studied as a function of collision centrality, as well as Υ transverse momentum and rapidity. No significant dependencies are observed