Nucleon Size Independence of Hadronic Nucleus-Nucleus Cross Sections

Abstract

Recent proposals to constrain the nucleon size using hadronic cross sections ($\sigma_{\rm AA}$) conflict with collective flow data. I demonstrate this dependence is an artifact of ``geometric inflation,'' where smearing point-like nucleons unintentionally dilutes the nuclear surface. By implementing a self-consistent framework that preserves the global nuclear density, I show that $\sigma_{\rm AA}$ is essentially insensitive to the nucleon width. This establishes $\sigma_{\rm AA}$ as a robust probe of the nuclear surface rather than the sub-nucleon scale. Utilizing this property, I extract a neutron skin thickness for $^{208}$Pb of $\Delta r_{\rm np} \in [0, 0.24]$~fm, providing an unconventional way to constrain the nuclear symmetry energy using high-energy hadronic observables.