Speaker
Description
In relativistic heavy-ion collisions, quasireal photons are highly linearly polarized, giving rise to characteristic azimuthal correlations in vector-meson decays. In ultra-peripheral collisions, the spin-interference effect can be quantified through the azimuthal modulation between the $J/\psi$ transverse momentum and its decay-lepton axis, providing sensitivity to the transverse spatial structure of the photonuclear interaction. In non-central hadronic collisions, the photon polarization inherited by the decay leptons can be measured relative to the event plane, offering direct access to the direction of the impact parameter.
In this contribution, we present measurements of the spin-interference-induced azimuthal modulation of photon-induced $J/\psi$ mesons in Ru+Ru, Zr+Zr, and Au+Au ultra-peripheral collisions at $\sqrt{s_{NN}}=200$ GeV. We also report measurements of the azimuthal anisotropy of electrons from photon-induced $J/\psi$ decays relative to the event plane in non-central Ru+Ru and Zr+Zr collisions at the same energy. Comparisons with theoretical model calculations and their physics implications will also be discussed.
