Light-nuclei production and search for the QCD critical point

TL;DR

This paper explores how measuring light nuclei in heavy-ion collisions can help identify the QCD critical point, proposing new ratios involving helium-4 and analyzing existing data to enhance detection prospects.

Contribution

It introduces novel ratios involving helium-4 to improve the search for the QCD critical point and demonstrates their potential through preliminary data analysis.

Findings

Ratios involving helium-4 show a more evident maximum near the critical point.

Preliminary STAR data suggests possible behavior consistent with critical phenomena.

Proposed measurements are feasible at current experimental facilities.

Abstract

We discuss the potential of light-nuclei measurement in heavy-ion collisions at intermediate energies for the search of the hypothetical QCD critical end-point. A previous proposal based on neutron density fluctuations has brought appealing experimental evidences of a maximum in a ratio involving tritons, protons and deuterons, ${\cal O}_{tpd}$. However these results are difficult to reconcile with the state-of-the-art statistical thermal model predictions. Based on the idea that the QCD critical point can lead to a substantial attraction among nucleons, we propose new ratios involving $^4$He in which the maximum would be more evident. We argue that the experimental extraction is feasible by presenting actual measurements at low and high collision energies. We also illustrate the possible behavior of these ratios at intermediate energies applying the semiclassical method based on flucton paths using preliminary STAR data for ${\cal O}_{tpd}$.