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

TL;DR

This study investigates how spectator nucleons influence light nuclei production in high-density nucleus-nucleus collisions, revealing that conventional methods underestimate yields due to low-$p_T$ enhancements from spectators.

Contribution

It demonstrates the significant impact of spectator effects on light nuclei yields and highlights the limitations of traditional extrapolation methods in such measurements.

Findings

Spectator nucleons cause low-$p_T$ enhancement in peripheral collisions.

Conventional extrapolations underestimate true light nuclei yields.

Spectator effects are prominent at forward rapidities.

Abstract

The light nuclei yields and yield ratios, as sensitive probes of the QCD phase transition, have been precisely measured at various collision energies.However, due to limited detector acceptance, the full $p_{\rm T}$ integral yield often requires extrapolation of the measured transverse momentum spectra to the unmeasured low-$p_{\rm T}$ region via functional fitting.Simulations with the AMPT-HC transport model and an after-burner coalescence approach indicate a significant low-$p_{\rm T}$ enhancement in peripheral collisions or forward rapidities, primarily originating from spectator nucleons.Consequently, conventional extrapolations tend to underestimate the true light nuclei yields.