Speaker
Wangmei Zha
(USTC/BNL)
Description
$J/\psi$ suppression in heavy-ion collisions due to color screening of quark and antiquark potential in the deconfined medium has been proposed as a signature of the QGP formation. Other mechanisms, such as the cold nuclear matter effects and charm quark recombination, are likely to contribute to the observed modification of $J/\psi$ production in heavy-ion collisions. Recently, a significant excess of $J/\psi$ yield at very low $p_{T}$ ($<$ 0.3 GeV/c) has been observed by the ALICE collaboration in peripheral hadronic Pb+Pb collisions at $\sqrt{s_{NN}}$= 2.76 TeV at forward-rapidity, which can not be explained within the scenarios mentioned above. The observed excess may originate from the coherent photoproduction of $J/\psi$, which would be very challenging for the existing coherent photoproduction models. Measurements of $J/\psi$ production at very low $p_{T}$ in different collision energies, collision systems, and centralities can shed new light on the origin of the excess .
In this presentation we report on the STAR measurements of $J/\psi$ production at very low $p_{T}$ in hadronic Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV at mid-rapidity. Centrality dependence of $J/\psi$ production and nuclear modification factors at very low $p_{T}$ will also be presented. Physics perspectives with Zr+Zr and Ru+Ru collisions will be discussed.
| On behalf of collaboration: | STAR |
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Author
Wangmei Zha
(USTC/BNL)
