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

Abstract

We report transverse momentum ($p_T\le 15$ GeV/$c$) spectra of $\ddot{I}{€}^{\pm }$, $K^{\pm }$, $p$, $\bar{p}$, $K_S^0$, and $\ddot{I}{}^0$ at mid-rapidity in p+p and Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV. Perturbative QCD calculations are consistent with $\ddot{I}{€}^{\pm }$ 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.

6 pages, 3 figures, published at PRL