A possible probe to neutron-skin thickness by fragment parallel momentum distribution in projectile fragmentation reactions

Neutron-skin thickness is a key parameter for a neutron-rich nucleus; however, it is difficult to determine. In the framework of the Lanzhou Quantum Molecular Dynamics (LQMD) model, a possible probe for the neutron-skin thickness ( \(\delta _\text {np}\) ${\delta }_{\text{np}}$ ) of neutron-rich \(^{48}\) ${}^{48}$ Ca was studied in the 140A MeV \(^{48}\) ${}^{48}$ Ca + \(^{9}\) ${}^9$ Be projectile fragmentation reaction based on the parallel momentum distribution ( \(p_\parallel \) $p_{\Vert }$ ) of the residual fragments. A Fermi-type density distribution was employed to initiate the neutron density distributions in the LQMD simulations. A combined Gaussian function with different width parameters for the left side ( \(\Gamma _\text {L}\) ${\mathrm{\Gamma }}_{\text{L}}$ ) and the right side ( \(\Gamma _\text {R}\) ${\mathrm{\Gamma }}_{\text{R}}$ ) in the distribution was used to describe the \(p_\parallel \) $p_{\Vert }$ of the residual fragments. Taking neutron-rich sulfur isotopes as examples, \(\Gamma _\text {L}\) ${\mathrm{\Gamma }}_{\text{L}}$ shows a sensitive correlation with \(\delta _\text {np}\) ${\delta }_{\text{np}}$ of \(^{48}\) ${}^{48}$ Ca, and is proposed as a probe for determining the neutron skin thickness of the projectile nucleus.