Abstract
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+psyst.), 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.
Highlights
In the study of the properties of the Quark–Gluon Plasma (QGP)an extensive effort has been devoted to measuring quarkonium yields since these have been predicted to be sensitive to color deconfinement [1]
For p + p collisions the minimum bias trigger is based on the STAR Beam-Beam Counters, while for d + Au and Au + Au it is based on the STAR Zero-Degree Calorimeters (ZDC) and the Vertex-Position Detectors (VPD)
In p + p collisions, we find a mass resolution of 1.3% for reconstructed Υ (1S)
Summary
In the study of the properties of the Quark–Gluon Plasma (QGP). An extensive effort has been devoted to measuring quarkonium yields since these have been predicted to be sensitive to color deconfinement [1]. Studies have mainly focused on charmonium, but with the high collision energies available at the Relativistic. One prediction is that excited quarkonium states are expected to dissociate at or above temperatures near that of the crossover to the deconfined QGP phase, Tc ≈ 150–190 MeV [3,4,5]. The more tightly bound ground states are expected to dissociate at even higher temperatures. The details of the temperature dependence of the dissociation of the excited states and of the feed-down pattern of the excited states into the ground state lead to a sequential suppression pattern of the inclusive upsilon states with increasing temperature [6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
