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

TL;DR

This study uses the Lanzhou quantum molecular dynamics model to explore how neutron-skin thickness affects pion emission in double-charge exchange reactions, providing insights into nuclear symmetry energy at subsaturation densities.

Contribution

It introduces a detailed analysis of neutron-skin effects on pion emission spectra in pion-induced reactions, linking experimental observables to neutron-skin thickness and nuclear symmetry energy.

Findings

Pion spectral ratios are sensitive to neutron-skin thickness.

Double-charge exchange reactions are affected by in-medium resonance properties.

Pion emission spectra can help constrain nuclear symmetry energy.

Abstract

Within the framework of Lanzhou quantum molecular dynamics (LQMD) transport model, we investigate the influence of the neutron-skin thickness of neutron-rich nuclei on the pion emission in the double-charge exchange reactions near the $\triangle$-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 $\triangle$-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.