1. If you are a new user, please register to get an Indico account through https://login.ihep.ac.cn/registIndico.jsp. Any questions, please email us at helpdesk@ihep.ac.cn or call 88236855.
2. The name of any uploaded file should be in English or plus numbers, not containing any Chinese or special characters.
3. If you need to create a conference in the "Conferences, Workshops and Events" zone, please email us at helpdesk@ihep.ac.cn.

# 第十七届全国中高能核物理大会

5-9 May 2017

Asia/Shanghai timezone
Home > Timetable > Contribution details

# Coherent very low transverse momentum $e^{+}e^{-}$ production in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR

• Dr. CHI YANG

## Summary

Recent ALICE collaboration measurements showed a significant excess in J/$\psi$ yield in the very low transverse momenta ($p_{T}$<0.3 GeV/$c$) in peripheral Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The same behavior of the J/$\psi$ production is observed at STAR in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. These results are interpreted as coherent photoproduction of J/$\psi$ at the moment. The coherent photonproduction scenario may also suggest there is an excess of photoproduced electron-positron production at the very low $p_{T}$ in peripheral collisions. It would be very interesting to investigate the electron-positron pair production in the full mass region ($M_{ee}<4$GeV/$c^{2}$) at very low $p_{T}$ in heavy-ion collisions in different centrality bins. If the coherent photoproduction mechanism confirmed, the coherently photoproduced $e^{+}e^{-}$ pairs accompanying violent hadronic collisions may provide a novel probe of the hot and dense nuclear matter.

In this talk, we will present $e^{+}e^{-}$ invariant mass spectra in very low $p_{T}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV. The $p_{T}$ spectra from different mass regions (0.4-0.76, 1.2-2.6, and 2.8-3.2 GeV/$c^{2}$) will be reported. The structure of t (-t = $p_{T}^{2}$ ) distributions of these mass regions and comparisons with that in ultra-peripheral collisions will be shown. The centrality dependence of the $e^{+}e^{-}$ productions will be shown. Physics messages will be discussed.