Speaker
Description
Ultra-strong electromagnetic field in relativistic heavy-ion collisions can generate a large flux of linearly polarized quasi-real photons. Photons emitted by one nucleus can interact with the other whole nucleus or individual nucleons to produce vector meson ($\gamma + A \rightarrow V + A$). On the other hand, interactions between photons emitted by two nuclei can produce lepton pairs ($\gamma + \gamma \rightarrow l^+ + l^-$). Notably, azimuthal asymmetries between the pair momentum and the daughter momentum could arise from the linear polarization of incident photons. The photon-induced vector mesons and lepton pairs carry information about the original electromagnetic field, which provides a sensitive probe to study the polarization dependent effects predicted by spin interference and QED vacuum birefringence.
In this presentation, we will report the angular modulation measurements of the photon-induced $J/\psi$ and $e^{+}e^{-}$ pair production in Ru+Ru, Zr+Zr and Au+Au peripheral and ultra-peripheral collisions at $\sqrt{s_{NN}}$ = 200 GeV. The angular modulation of $\mu^{+}\mu^{-}$ pairs in Au+Au peripheral collisions will also be presented. Physics implications of these results will be discussed together with model comparisons.
