Effects of neutron-skin thickness on direct hard photon emission from reactions induced by the neutron-rich projectile $^{50}$Ca

TL;DR

This study uses simulations to explore how neutron skin thickness in neutron-rich nuclei affects direct hard photon emission in nuclear collisions, proposing a new observable for neutron skin measurements.

Contribution

It demonstrates that direct hard photon emission is sensitive to neutron skin thickness, providing a novel experimental probe for nuclear structure studies.

Findings

Photon yield increases with neutron skin thickness in peripheral collisions.

Photon multiplicity ratio R_{cp}(σ_γ) is sensitive to neutron skin thickness.

Rapidity distribution of photons varies with neutron skin, indicating potential for experimental extraction.

Abstract

Direct hard photon emissions from incoherent proton-neutron bremsstrahlung in collisions of the neutron-rich projectile $^{50}$Ca with $^{12}$C and $^{40}$Ca targets are simulated in the framework of the isospin-dependent quantum molecular dynamics (IQMD) model. By adjusting the diffuseness parameter of neutron density in the droplet model to obtain different neutron skin thicknesses for $^{50}$Ca, the effects of neutron skin thickness on direct hard photon emission are investigated via several probes. The results show that more direct hard photons are produced with increasing neutron skin thickness in peripheral collisions. Meanwhile, we find that the multiplicity yield ratio $R_{cp}(\sigma_{\gamma})$ between central collisions and peripheral collisions as well as the rapidity dependence of multiplicity for direct hard photons are sensitive to neutron skin thickness. The results indicate that direct hard photon emission can be taken as an experimental observable to extract information on neutron skin thickness.