Using local nuclear scaling of initial condition parameters to improve the system size dependence of transport model descriptions of nuclear collisions

TL;DR

This paper introduces a local nuclear scaling approach for initial condition parameters in a transport model, enabling consistent description of system size and centrality dependence across various collision systems and energies.

Contribution

The study develops a local nuclear thickness scaling method for key model parameters, improving the description of diverse nuclear collision data within a unified framework.

Findings

Accurately describes $pp$ collisions from 23.6 GeV to 13 TeV.

Provides reasonable centrality dependence of charged particle yields in heavy-ion collisions.

Successfully models smaller systems like $p$Pb, Cu+Cu, and Xe+Xe.

Abstract

We extensively study the system size dependence of nuclear collisions with a multi-phase transport model. Previously certain key parameters for the initial condition needed significantly different values for $pp$ and central $AA$ collisions for the model to reasonably describe the yields and transverse momentum spectra of the bulk matter in those collision systems. Here we scale two key parameters, the Lund string fragmentation parameter $b_L$ and the minijet transverse momentum cutoff $p_0$, with local nuclear thickness functions from the two colliding nuclei. This allows the model to use the parameter values for $pp$ collisions with the local nuclear scaling to describe the system size and centrality dependences of nuclear collisions self consistently. In addition to providing good descriptions of $pp$ collisions from 23.6 GeV to 13 TeV and reasonable descriptions of the centrality dependence of charged particle yields for Au+Au collisions from $7.7A$ GeV to $200A$ GeV and Pb+Pb collisions at LHC energies, the improved model can now well describe the centrality dependence of the mean transverse momentum of charged particles below $p_{\rm T} \lesssim 2$ GeV. It works similarly well for smaller systems including $p$Pb, Cu+Cu and Xe+Xe collisions.