New proxies for second-order cumulants of conserved charges in heavy-ion collisions within the EPOS4 framework

Proxies for cumulants of baryon number <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>B</a:mi></a:math>, electric charge <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>Q</b:mi></b:math>, and strangeness <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mi>S</c:mi></c:math> are usually measured in heavy-ion collisions via moments of net-number distribution of given hadronic species. Since these cumulants of conserved charges are expected to be sensitive to the existence of a critical point in the phase diagram of nuclear matter, it is crucial to ensure that the proxies used as substitutes are as close to them as possible. Hence, we use the 4 framework to generate <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mtext>Au</d:mtext><d:mo>+</d:mo><d:mtext>Au</d:mtext></d:mrow></d:math> collisions at several collision energies of the BNL Relativistic Heavy Ion Collider beam energy scan. We compute second-order net cumulants of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>π</e:mi></e:math>, <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mi>K</f:mi></f:math>, and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mi>p</g:mi></g:math>, for which experimental data have been published as well as the corresponding conserved charge cumulants. We then compare them with proxies, defined in previous lattice QCD and hadron resonance gas model studies, which are shown to reproduce more accurately their associated conserved charge cumulants. We investigate the impact of hadronic rescatterings occurring in the late evolution of the system on these quantities, as well as the amount of signal actually originating from the bulk medium which endures a phase transition. Published by the American Physical Society 2024