Extended Statistical Thermal Model and Rapidity Spectra of Hadrons at 200 GeV/A

TL;DR

This paper extends the statistical thermal model to successfully describe rapidity spectra of various hadrons at 200 GeV/A RHIC energy, incorporating local strangeness conservation and resonance decay effects.

Contribution

The paper introduces an extended thermal model with a unified temperature and rapidity-dependent chemical potentials to fit multiple hadron spectra at high energy.

Findings

Model accurately reproduces rapidity spectra of protons, antiprotons, kaons, and pions.

The model explains net proton distribution and nuclear transparency effects.

Resonance decay contributions are consistent with experimental data.

Abstract

We use the extended statistical thermal model to describe various hadron rapidity spectra at the highest RHIC energy (200 GeV/A). The model assumes the formation of hot and dense regions moving along the beam axis with increasing rapidities, yFB. It has been earlier shown that this model can explain the net proton flow i.e. p minus pbar, ratio pbar/p and the pion rapidity spectra. In this paper we have attempted to show that in addition to these quantities, this model can also successfully describe the individual rapidity spectra of protons, antiprotons, Kaons, antiKaons, pions, the ratios lambdabar/lambda and cascadebar/cascade. The experimental data set on p, pbar, K, Kbar and Pion provided by BRAHMS collaboration at the highest energy of Relativistic Heavy Ion Collider, sqrt(SNN) = 200 GeV are used. The theoretical results fit quite well with mid-rapidity data (for y < 1) of the lambdabar/lambda and the cascadebar/cascade ratios available (from STAR). We have used single set of model parameters including single value of the temperature parameter T for all the regions of the hot and dense matter formed. The chemical potentials are however assumed to be dependent on the fireball rapidity yFB. We have analyzed the contribution of the decay of the heavier resonances to the proton (antiproton) rapidity spectra. It is found that the rapidity spectrum of the product hadron is nearly same as that of the parent hadron. We have also imposed the criteria of exact strangeness conservation in every (local) region of the dense matter separately, which is necessary. We also discuss what can be learned about the nuclear transparency effect at the highest RHIC energy from the net proton rapidity distribution.