Description
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Title: Probe the Quark Gluon Plasma with Quarkonia at the STAR Experiment
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Speaker: Rongrong Ma (Brookhaven National Laboratory)
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Abstract: The quark-gluon plasma (QGP) is believed to have existed in the early universe, and can be created in laboratory through ultra-relativistic heavy-ion collisions. Among various probes used to study the properties of the QGP, quarkonia play a special role as they are expected to dissociate in the medium due to the color screening of the quark-antiquark potential by the surrounding partons. Such a dissociation occurs when the quarkonium size exceeds the medium Debye radius, which is inversely proportional to the medium temperature. Consequently, quarkonium suppression was proposed as a direct evidence of the QGP formation in heavy-ion collisions. Furthermore, the three bottomonium states of different binding energies are expected to dissociate at different temperatures, which can be used to constrain the temperature of the QGP. To aid the interpretation of the observed quarkonium suppression in heavy-ion collisions, the corresponding Cold Nuclear Matter (CNM) effects, arising from the presence of heavy nuclei in the collisions but not related to the QGP, also need to be understood.
In this talk, I will discuss the latest measurements of J/𝜓 and ϒ production in p+p collisions at sqrt(s) = 200 and 500 GeV, as well as in p+Au and Au+Au collisions at sqrt(sNN) = 200 GeV by the STAR experiment at RHIC. The J/𝜓 suppression in Au+Au collisions is measured as functions of J/𝜓 transverse momentum (pT) over a wide range, and of collision geometry. A strong suppression of high-pT J/𝜓 is observed in central Au+Au collisions. On the other hand, a sequential suppression pattern is observed for the ϒ family, with the excited states more suppressed than the ground state. These measurements are compared with model calculations and physics implications will be discussed.
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CV: I graduated from the Peking University in 2008 with a Bachelor's degree, and went onto the Yale University as a Ph. D candidate. During my graduate years, I worked on measurements of inclusive jet cross-section in p+p collisions and semi-inclusive jet suppression in heavy-ion collisions with the ALICE experiment at CERN. After receiving my Ph. D. from Yale, I came to the Brookhaven National Laboratory first as a post-doc, and then as a Goldhaber Fellow. I also transitioned to carry out quarkonium measurements in heavy-ion collisions utilizing the Muon Telescope Detector fully installed in 2014. I became an assistant physicist at BNL in 2017, and then an associate physicist until now. My research interests are using quarkonium and heavy-flavor jets to study the properties of the quark-gluon plasma.
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