The azimuthal asymmetries in ρ0 production in UPCs

• Cheng Zhang (Shandong University)

We compute the unpolarized cross section and cos2φ azimuthal asymmetry for ρ0 photoproduction with φ defined as the angle between the ρ0’s transverse momentum and its decay product pion meson’s transverse momentum. Our result on unpolarized cross section gives excellent description to the STAR experimental data. Our first calculation on the cos2φ azimuthal asymmetry, which results from the linearly polarized photons, also shows reasonable agreement with the experimental measurement. We further study the Coulomb nuclear interference process where the pion pair can either be produced via two photon fusion or from the ρ0 decay in photonuclear reaction, which gives rise to sizable cosφ and cos3φ azimuthal asymmetries.