Probing configuration of α clusters with spectator particles in relativistic heavy-ion collisions

Abstract

We propose to use spectator particle yield ratios to probe the configuration of α clusters in 12C and 16O by their ultracentral collisions at RHIC and LHC energies. The idea is illustrated based on initial density distributions with various α-cluster configurations generated by a microscopic cluster model, and without α clusters from mean-field calculations. The multifragmentation of the spectator matter produces more spectator light nuclei including α clusters in collisions of nuclei with chain structure of α clusters, compared to those of nuclei with a more compact structure. The yield ratio of free spectator neutrons to spectator particles with mass-to-charge ratio A/Z=2 scaled by their masses can be practically measured by the zero-degree calorimeter (ZDC) at RHIC and LHC, serving as a clean probe free from modeling the complicated dynamics at midrapidities.