Identified hadron compositions in p+p and Au+Au collisions at high transverse momenta at $\sqrt{s_{_{NN}}} = 200$ GeV

TL;DR

This study measures high-$p_T$ hadron spectra in p+p and Au+Au collisions at 200 GeV, revealing differences in particle ratios and testing perturbative QCD predictions, with implications for understanding jet contributions and energy loss.

Contribution

It provides detailed high-$p_T$ hadron spectra and compares particle ratios in p+p and Au+Au collisions, highlighting the consistency and discrepancies with theoretical models.

Findings

Perturbative QCD matches $ o$ spectra for pions in p+p but not for kaons and protons.

Antiparticle-to-particle ratios decrease with increasing $p_T$, indicating varying jet contributions.

Hadron abundances in Au+Au at high $p_T$ are similar to p+p results, despite expected energy loss effects.

Abstract

We report transverse momentum ($p_{T} \leq15$ GeV/$c$) spectra of $\pi^{\pm}$, $K^{\pm}$, $p$, $\bar{p}$, $K_{S}^{0}$, and $\rho^{0}$ at mid-rapidity in p+p and Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV. Perturbative QCD calculations are consistent with $\pi^{\pm}$ spectra in p+p collisions but do not reproduce $K$ and $p(\bar{p})$ spectra. The observed decreasing antiparticle-to-particle ratios with increasing $p_T$ provide experimental evidence for varying quark and gluon jet contributions to high-$p_T$ hadron yields. The relative hadron abundances in Au+Au at $p_{T}{}^{>}_{\sim}8$ GeV/$c$ are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.