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

Abstract

Direct hard photon emissions from incoherent proton-neutron bremsstrahlung in the collisions of neutron-rich projectile 50 Ca with 12 C and 40 Ca targets are simulated in the framework of IQMD model, respectively. By adjusting the diffuseness parameter of neutron density in the droplet model to obtain different neutron skin thickness 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 the increasing of the neutron skin thickness. Meanwhile, we find that yield ratio Rcp(σγ) and the rapidity dependence of multiplicity and multiplicity ratio Rcp(Nγ) for direct hard photons are apparently sensitive to neutron skin thickness. Furthermore, the direct hard photon differential and relative flows between central and peripheral collision are presented. We find that the differential flow is slightly more sensitive to neutron skin thickness than the relative flow. It is suggested that direct hard photon emission may be used as an experimental observable to extract the information of neutron skin thickness.