Nuclear Deformation Effects on Charmonium Suppression in Au+Au and U+U Collisions

Abstract

We investigate the impact of intrinsic nuclear deformation and orientation on the yield suppression and momentum anisotropy of charmonia in Au+Au and U+U collisions at the Relativistic Heavy-Ion Collider. The anisotropic nucleon density within the nucleus is parameterized using a modified Woods-Saxon distribution, which is incorporated into the initial distributions of both the heavy quarkonia and the bulk medium energy density. The well-established Boltzmann-type transport equation is utilized to describe the dynamical evolution of quarkonium in the anisotropic bulk medium. Treating quarkonium suppression in Au+Au collisions as a baseline, we find that the momentum-integrated charmonium yield suppression is relatively insensitive to the initial nuclear geometry in deformed U+U collisions. In contrast, the anisotropic flow coefficients ($v_n$) of the charmonium is more sensitive to the nuclear deformation. Furthermore, these observables are also connected with the collision configuration, particularly when distinguishing between tip-tip and body-body orientations in U+U collisions at $\sqrt{s_{NN}} = 193$ GeV. This effect is more pronounced for the excited state due to its smaller binding energy and heightened sensitivity to the initial energy density of the hot QCD medium.

Figures (9)

• Figure 1: $J/\psi$ decay rate $\alpha_{J/\psi}(T)$ attributed to the inelastic scatterings with thermal gluons as a function of temperatures, the transverse momentum of $J/\psi$ is set to be $p_T=0$ used in Eq.(\ref{['lab-decayrate']}).
• Figure 2: Schematic illustration of the impact of the triaxiality angle $\gamma$ in Eq. (\ref{['eq:R_deformed']}) on the initial geometry of the overlap between two nuclei. Ellipsoids denote the deformed nuclei; red arrows indicate the beam ($z$-) direction. The gray contours on the right show the transverse overlap projection for $\gamma=0^\circ,\,30^\circ,\,60^\circ$.
• Figure 3: Definition of the idealized tip-tip and body-body configurations at $\gamma=0^\circ$. Tip-tip: the long axes of both nuclei are aligned with the beam ($z$) direction; body-body: the long axes lie in the transverse plane. The gray contours on the right show the corresponding transverse overlap projections.
• Figure 4: Initial entropy density profiles $s_n(\tau_0, x, y)$ for 200 GeV deformed Au+Au (left), and 193 GeV deformed U+U (right) collisions at the initial time $\tau = \tau_0$. The sub-panels display collision centralities of 0–10% and 0–80%, respectively. The Bohr triaxiality angle $\gamma$ is set to $0^\circ, 30^\circ, \text{and } 60^\circ$ within the nuclear density distribution for Uranium ($U$).
• Figure 5: Initial entropy density profiles $s_n(\tau_0, x, y)$ for deformed Au+Au (left), and deformed U+U (right) collisions. Both tip-tip and body-body configurations with a Bohr triaxiality angle $\gamma = 0^\circ$ are displayed.