Probing the neutron-skin thickness via the double-charge exchange reactions in pion-nucleus collisions

Original data on the pion emission in the double-charge exchange reactions near the Delta-resonance energy, in particular, the rapidity and transverse momentum spectra, charged pion ratios et al. The reactions induced by pions are associated with the multiple processes of pions, nucleons and Delta-resonances, correlated with the neutron-skin thickness. It is found that the kinetic energy spectra of \pi-/\pi+ ratio are sensitive to the neutron-skin thickness of neutron-rich nuclei for extracting the subsaturation-density symmetry energy.

The double-charge exchange reactions are influenced by the neutron-skin thickness, in-medium properties of resonances, pion-nucleon potential and pion-nucleon scattering. Possible measurements are proposed in the future experiments at high-intensity heavy-ion accelerator facility (HIAF) in Huizhou.