Speaker
Jian Zhou
(University of Science and Technology of China)
Description
Recently, significant enhancements of $e^{+}e^{-}$ pairs at very low transverse momentum ($p_{T}$) were observed by the STAR collaboration in peripheral Au+Au collisions. The excess can be explained by photon-photon interactions induced by the extremely strong electromagnetic field produced by the fast-moving heavy ions. While such photon-photon interactions were traditionally studied in ultra-peripheral collisions without any nuclear overlaps, they could provide a novel probe to the Quark Gluon Plasma(QGP) created in peripheral collisions since the very-low-$p_{T}$ dileptons are produced in the early stage of the collisions. Furthermore, the photon-photon interactions could be used to probe the possible existence of strong magnetic field trapped in a conducting QGP medium. Measurements of $\mu^{+}\mu^{-}$ pairs provide a complementary channel to investigate these phenomena.
In 2014 and 2016, the STAR experiment at RHIC recorded large samples of Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. In this talk, we will present new measurements of invariant mass and yield distributions for $\mu^{+}\mu^{-}$ pair production at $p_{T} < 0.1 $ GeV/$c$. The $p_{T}^{2}$ distribution of the excess yields will also be shown. Physics implications will be discussed together with model comparisons.
Primary author
Jian Zhou
(University of Science and Technology of China)
