Forward J/ψ production in U + U collisions at √ sNN = 193 GeV
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The invariant yields, dN/dy, for J/ψ production at forward rapidity (1.2<|y|<2.2) in U+U collisions at sNN−−−√=193GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor RAA are presented and compared with those from Au+Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U+U and Au+Au collisions within the same centrality class is presented, and used to investigate the role of cc¯ coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, Ncoll, and these were found to give significantly different Ncoll values. Results using Ncoll values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the J/ψ suppression, relative to binary collision scaling, is similar in U+U and Au+Au for peripheral and midcentral collisions, but that J/ψ show less suppression for the most central U+U collisions. The results are consistent with a picture in which, for central collisions, increase in the J/ψ yield due to cc¯ coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between cc¯ coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine Ncoll.
- Physical review C
Physical review C 93(3), 034903, 2016-03
American Physical Society