Measuring neutron skin by grazing isobaric collisions

Understand

Neutron skin thickness ($\Delta r_{\rm np}$) of nuclei and the inferred nuclear symmetry energy are of critical importance to nuclear physics and astrophysics.

• It is traditionally measured by nuclear processes with significant theoretical uncertainties.
• We recently proposed an indirect measurement of the $\Delta r_{\rm np}$ by charged hadron multiplicities in central isobaric collisions at relativistic energies, which are sensitive to nuclear densities.
• In this Letter, we propose a direct measurement of the $\Delta r_{\rm np}$ by using net-charge multiplicities in ultra-peripheral (grazing) collisions of those isobars, under the assumption that they are simple superimposition of nucleon-nucleon interactions.