Neutron skin and its effects in heavy-ion collisions

Abstract Neutron skin is an exotic phenomenon that occurs in unstable nuclei. In this study, the various effects of the neutron skin on nuclear reactions and their relationship with the properties of nuclear structures are reviewed. Based on numerous studies using theoretical models, strong correlations have been found between the neutron skin thickness and the neutron removal cross section, neutron/proton yield ratio, $$\hbox {t}/{^3\hbox {He}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>t</mml:mtext> <mml:mo>/</mml:mo> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> <mml:mtext>He</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> yield ratio, neutron–proton momentum difference, isoscaling parameter, photon production, reaction cross sections for neutron-induced reactions, charge-changing cross-sectional differences of mirror nuclei, astrophysical S -factor, and other quantities in nuclear reactions induced by neutron-rich nuclei. Moreover, the relationships between the neutron skin thickness and certain properties of the nuclear structure, such as $$\alpha$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>α</mml:mi> </mml:math> -cluster formation, $$\alpha$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>α</mml:mi> </mml:math> decay, nuclear surface, nuclear temperature, and proton radii difference of mirror nuclei, have also been investigated. Furthermore, it has also been shown that the neutron skin plays a crucial role in relativistic heavy-ion collisions. Experimentally, an unstable nucleus with a neutron skin can be generated by radioactive nuclear beam facilities, and the thickness of the neutron skin can be extracted by measuring the sensitive probes, which further helps impose stringent constraints on the equation of state of asymmetric nuclear matter and the properties of neutron stars.