Physics Letters B
We report measurements of ϒ meson production in p + p, d + Au, and Au + Au collisions using the STAR detector at RHIC. We compare the ϒ yield to the measured cross section in p + p collisions in order to quantify any modifications of the yield in cold nuclear matter using d + Au data and in hot nuclear matter using Au + Au data separated into three centrality classes. Our p + p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for ϒ (1S + 2S + 3S) in the rapidity range | y | < 1 in d + Au collisions of RdAu = 0.79 ± 0.24(stat.) ± 0.03(syst.) ± 0.10(p + p syst.). A comparison with models including shadowing and initial state parton energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au + Au collisions, we measure a nuclear modification factor of RAA = 0.49 ± 0.1(stat.) ± 0.02(syst.) ± 0.06(p + p syst.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state ϒ mesons in Au + Au collisions. The additional suppression in Au + Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark-Gluon Plasma. However, understanding the suppression seen in d + Au is still needed before any definitive statements about the nature of the suppression in Au + Au can be made.
Original Publication Citation
Adamczyk, L., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z., Alekseev, I., . . . Star, C. (2014). Suppression of ϒ Production in d + Au and Au + Au collisions at √Sɴɴ = 200 GeV. Physics Letters B, 735, 127-137. doi: 10.1016/j.physletb.2014.06.028
Adamczyk, L.; Adkins, J.K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Bültmann, S.; and Plyku, Donika, "Suppression of ϒ Production in d + Au and Au + Au collisions at √Sɴɴ = 200 GeV" (2014). Physics Faculty Publications. 52.