J/ polarization in relativistic heavy ion collisions

Abstract Understanding the polarization property of J/ J / ψ is critical to constrain its production mechanism. In addition, the polarization of J/ J / ψ can reveal the impact of strong electromagnetic and vorticity fields in relativistic heavy ion collisions. In this study, we analyzed the yield and polarization of J/ J / ψ in relativistic heavy ion collisions at different centrality and transverse momentum regions, using three different reference frames: the Collins–Soper frame, the helicity frame, and the event plane frame. The polarization of initially produced J/ J / ψ is determined by the NRQCD calculation and is similar to that of pp collisions. However, both unpolarization and transverse polarization are considered for the regenerated J/ J / ψ. Our results indicate that the polarization at high pT p T is similar to that observed in pp collisions. However, at low pT p T, where regenerated J/ J / ψ dominates, it is likely that the polarized charm quarks in the rotational QGP medium are responsible for this phenomenon. Our study supplies a baseline for future research on the effects of strong electromagnetic and vorticity fields on J/ J / ψ polarization.