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

We report transverse momentum ($p_{T} \leq15$GeV\mathrm{/}$c$)spectraof$\pi^{\pm}$,$K^{\pm}$,$p$,$\bar{p}$,$K_{S}^{0}$,and$\rho^{0}$atmid-rapidityinp+pandAu+Aucollisionsat$\sqrt{s_{_{NN}}}$=200GeV\mathrm{.}PerturbativeQCDcalculationsareconsistentwith$\pi^{\pm}$spectrainp+pcollisionsbutdonotreproduce$K$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.