Baryon spectra and antiparticle-to-particle ratios from the improved AMPT model

Yuncun He,Zi-Wei Lin,A Mischke,P Kuijer

doi:10.1051/epjconf/201817114004

Yuncun He, Zi-Wei Lin + Show 2 more

Open Access

https://doi.org/10.1051/epjconf/201817114004

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Abstract

The current version of a multi-phase transport (AMPT) model with string melting can reasonably describe the dN/dy yields, pT spectra and anisotropic flows of pions and kaons at low pT in heavy ion collisions at RHIC and LHC energies, although it failed to reproduce the dN/dy and pT spectra of baryons. In this work, we improve the quark coalescence mechanism in AMPT by removing the forced separate number conservations of mesons, baryons and antibaryons in each event. We find that the improved AMPT model can better describe the yields at midrapidity, the pT spectra and elliptic flow of low-pT baryons in comparison with the experimental data. Antiparticle-to-particle ratios of strange baryons are also significantly improved.

Highlights

The original string melting version of a multi-phase transport (AMPT) [1], which converts all the excited strings to partons before parton cascade and hadronizes with the quark coalescence mechanism, could fit the elliptic flow and two-pion interferometry at RHIC very well, but it failed to reproduce the pT spectra and rapidity distributions of hadrons
The thin curves represent results produced by the old quark coalescence, which gives higher yields at midrapidity and too soft pT spectra at both RHIC and LHC
The thick curves represent results produced by the new quark coalescence, which gives lower yields and harder pT spectra and is more consistent with the data

Summary

Introduction

The original string melting version of AMPT [1], which converts all the excited strings to partons before parton cascade and hadronizes with the quark coalescence mechanism, could fit the elliptic flow and two-pion interferometry at RHIC very well, but it failed to reproduce the pT spectra and rapidity distributions of hadrons. PT spectra and GeV and 2.76 elliptic flows of TeV [2] It has pions and been used to predict the identified particles correlations in the Pb+Pb collisions at. PT spectra, azimuthal anisotropies and 5.02 TeV [3] It still has some longitudinal deficiencies on baryon descriptions. A new constant parameter rBM, which controls the relative probability of a quark forming a baryon versus a meson, is introduced and its value has been determined by fitting the experimental data [4]. Note that in principle this parameter should be determined from the hadron wavefunctions In this new AMPT model, we use the Lund string fragmentation parameters a = 0.55 for Au+Au collisions at 200 GeV and a = 0.2 for Pb+Pb collisions at 2.76 TeV respectively, and b = 0.15 GeV−2 for both collisions.

Results for protons and antiprotons

Results for antiparticle-to-particle ratios

Conclusion