Investigation of the Spectator Effect on Light Nuclei Production in Nucleus-Nucleus Collisions at High Baryon Density Region

Abstract

The light nuclei yields and their yield ratios, regarded as sensitive probes of the QCD phase structure, have been extensively measured at various collision energies. However, due to limited detector acceptance, the $p_{\rm T}$-integrated yield is often obtained by extrapolating from the measured $p_{\rm T}$ spectrum to the unmeasured low-$p_{\rm T}$ region using model-based fits. Simulations using AMPT-HC combined with an after-burner coalescence approach indicate a significant enhancement of light nuclei production at low $p_{\rm T}$, particularly in peripheral collisions and at forward rapidities, driven primarily by spectator nucleons. As a result, standard extrapolation procedures may systematically miss this additional low-$p_{\rm T}$ component, leading to an underestimate of the $p_{\rm T}$-integrated light-nucleus yields in such scenarios.