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1–5 Sep 2017
China National Convention Center
Asia/Shanghai timezone

Excess of $J/\psi$ yield at very low $p_{T}$ in Au+Au collisions at $\sqrt{s_{\text{NN}}}$ = 200 GeV and U+U collisions at $\sqrt{s_{\text{NN}}}$ = 193 GeV measured with the STAR experiment

1 Sep 2017, 14:25
25m
302A (China National Convention Center)

302A

China National Convention Center

No.7 Tianchen East Road, Chaoyang District, Beijing 100105 China
1) Hot and dense matter physics (QGP and heavy ion collision) Hot and dense matter physics (QGP and heavy ion collision)

Speaker

王妹 查 (中国科学技术大学近代物理系)

Description

Suppression of J/ψ production 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 J/ψ regeneration from charm quark-antiquark recombination in the medium, can contribute to the observed modification of the J/ψ production in heavy-ion collisions. Unexpectedly, a significant excess of the J/ψ yield at very low transverse momenta (pT< 0.3 GeV/c) was observed by the ALICE collaboration in peripheral Pb+Pb collisions at sNN‾‾‾‾√ = 2.76 TeV at forward-rapidity, which can not be explained by the aforementioned effects. It has been hypothesized that such J/ψ's are produced in the coherent photoproduction in Pb+Pb collisions at impact parameters smaller than twice the nuclear radius, which would be very challenging for the existing models developed to describe the coherent photoproduction in ultra-peripheral collisions. Measurements of J/ψ production at very low pT for different collision energies, collision systems, and collision geometries can shed new light on the origin of the excess.\ In this presentation we report the STAR measurements of J/ψ production at very low pT in Au+Au collisions at sNN‾‾‾‾√ = 200 GeV and U+U collisions at sNN‾‾‾‾√ = 193 GeV at mid-rapidity. Centrality and pT dependencies of J/ψ production cross sections and nuclear modification factors will be presented.

Primary author

王妹 查 (N)

Presentation materials