Parton coalescence at RHIC

TL;DR

This paper presents a covariant coalescence model for hadron production in relativistic heavy ion collisions at RHIC, successfully describing experimental spectra, particle ratios, and elliptic flows by incorporating soft and hard parton dynamics.

Contribution

It introduces a comprehensive coalescence model that includes transverse flow and minijet fragmentation, providing improved agreement with experimental data on hadron spectra and flow at RHIC.

Findings

Antiproton to pion ratio increases at low transverse momentum and reaches about one at intermediate momenta.

Model predicts decreasing particle ratios at high transverse momenta approaching pQCD results.

Elliptic flow calculations are consistent with experimental measurements.

Abstract

Using a covariant coalescence model, we study hadron production in relativistic heavy ion collisions from both soft partons in the quark-gluon plasma and hard partons in minijets. Including transverse flow of soft partons and independent fragmentation of minijet partons, the model is able to describe available experimental data on pion, kaon, and antiproton spectra. The resulting antiproton to pion ratio is seen to increase at low transverse momenta and reaches a value of about one at intermediate transverse momenta, as observed in experimental data at RHIC. A similar dependence of the antikaon to pion ratio on transverse momentum is obtained, but it reaches a smaller value at intermediate transverse momenta. At high transverse momenta, the model predicts that both the antiproton to pion and the antikaon to pion ratio decrease and approach those given by the perturbative QCD. Both collective flow effect and coalescence of minijet partons with partons in the quark-gluon plasma affect significantly the spectra of hadrons with intermediate transverse momenta. Elliptic flows of protons, Lambdas, and Omegas have also been evaluated from partons with elliptic flows extracted from fitting measured pion and kaon elliptic flows, and they are found to be consistent with available experimental data.