Separating the impact of nuclear skin and nuclear deformation on elliptic flow and its fluctuations in high-energy isobar collisions

Bulk nuclear structure properties, such as radii and deformations, leave distinct signatures in the final states of relativistic heavy-ion collisions. Collisions of isobars, in particular, offer an easy route to establish clear correspondences between the structure of colliding nuclei and the final state observables. Here we investigate the impact of nuclear skin and nuclear deformations on elliptic flow ($v_2$) and its fluctuations in high-energy $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions, for which experimental data is available. We show that the difference in skin thickness between these isobars impacts the intrinsic ellipticity of the collision systems, or reaction-plane flow, $v_2^{\mathrm{rp}}$. In contrast, differences in nuclear deformations impact only the fluctuations of $v_2$ around $v_2^{\mathrm{rp}}$. Through isobar collisions, one can separate the influence of nuclear skin and nuclear deformations in the $v_2$ data. This is a significant step towards assessing the consistency of nuclear phenomena across energy scales.