Baseline study for net-proton number fluctuations at top energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider with the Angantyr model

TL;DR

This study uses the Angantyr model to analyze net-proton number fluctuations in heavy-ion collisions at top energies, providing baseline predictions unaffected by thermalization assumptions.

Contribution

It offers the first baseline estimates of net-proton cumulants at top collider energies using the Angantyr model, including effects of flow and decays.

Findings

Radial flow significantly affects cumulants and ratios.

Weak decays have a smaller but noticeable impact.

Baseline values can guide future experimental measurements.

Abstract

The multiplicity percentile dependence of cumulants, of net-proton number distributions in Au$-$Au collisions at $\sqrt{s_{NN}} = $ 200 GeV and Pb$-$Pb collisions at $\sqrt{s_{NN}} = $ 2.76 TeV has been investigated using the Angantyr model (the heavy-ion extension of the \textsc{Pythia 8} model). The effects of finite transverse momentum ($p_{\mathrm T}$) and pseudorapidity ($\eta$) acceptance on the net-proton cumulants have also been studied. Furthermore, the effects of the hydrodynamic expansion and feed down from weak decays were explored. It was found that radial flow has substantial impact on the cumulants and their ratios, while weak decays have a finite but relatively smaller effect. The obtained values of cumulants and their ratios with the Angantyr model, where the formation of thermalized medium is not assumed can serve as a baseline for future measurements.