BNL
 
STAR focus: Identified hadron compositions in p+p and Au+Au collisions at high transverse momenta at √sNN = 200 GeV

The invariant yields d2N/(2πpTdpTdy) of π±, K±, K0S, ρ0, p, and pbar from non-singly diffractive p+pcollisions (σNSD=30.0±3.5 mb), those of K+p(pbar), K0S, and ρ0, in central Au+Au collisions, and NLO calculations with AKK and DSS FFs. The uncertainty of yields due to the scale dependence as evaluated in DSS calculations is about a factor of 2. Bars and boxes (bands) represent statistical and systematic uncertainties, respectively.

Yield ratios π-+, pbar/p, K-/K+, p/π+, pbar/π-, and K±, K0S± versus pT in p+p collisions, and nominal NLO calculations with AKK and DSS FFs without theoretical uncertainties. The open squares in panels (d) and (e) are the p/π+ and pbar/π- ratios in central Au+Au collisions with updated uncertainties at high pT, and all other data points are from p+p collisions. Bars and boxes (bands) represent statistical and systematic uncertainties, respectively.

(a) RAA of K±+p(pbar), K0S, ρ0, and π± in central Au+Au collisions as a function of pT. The curves are the calculations for K0S RAAwith and without jet conversion in medium. Bars and boxes (bands) represent statistical and systematic uncertainties, respectively. The height of the band at unity represents the normalization uncertainty. (b) The ratios of RAA[K±+p(pbar), ρ0] to RAA±) and RAA(K-+pbar) to RAA(K++p). The boxes and shaded bands represent the systematic uncertainties for RAA0)/RAA±) and RAA[K±+p(pbar)]/RAA±), respectively. The systematic uncertainties for RAA(K-+pbar)/RAA(K++p) are 2--12% and left off for clarity.

We report identified particle pT spectra at mid-rapidity up to 15 GeV/c from p+p and Au+Au collisions at √sNN = 200 GeV. The NLO pQCD models describe the π± spectra but fail to reproduce the K and p(pbar) spectra at high pT. The measured anti-particle to particle ratios are observed to decrease with increasing pT. This reflects differences in scattering contributions to the production of particles and anti-particles at RHIC. At pT≥8 GeV/c, a common suppression pattern is observed for different particle species. Incorporating our p+p data in generating the flavor separated FFs in the same kinematic range will provide new inputs and insights into the mechanisms of jet quenching in heavy ion collisions.


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