Charged hadron transverse momentum distributions in Au+Au collisions at sqrt(s_NN) = 200 GeV

Abstract

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at sqrt(s_NN) = 200 GeV. The spectra were measured for transverse momenta p_T from 0.25 to 4.5 GeV/c in a rapidity range of 0.2 < y_pi < 1.4. The evolution of the spectra is studied as a function of collision centrality, from 65 to 344 participating nucleons. The results are compared to data from proton-antiproton collisions and Au+Au collisions at lower RHIC energies. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. Comparing peripheral to central Au+Au collisions, we find that the yields at high p_T exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

Figures (4)

• Figure 1: Invariant yields for charged hadrons as a function of $p_T$ for 6 centrality bins. For clarity, consecutive bins are scaled by factors of 10. Statistical and systematic uncertainties are smaller than the symbol size.
• Figure 2: Ratio of the yield of charged hadrons as a function of $p_T$ for the most peripheral bin ($\langle N_{part} \rangle = 65 \pm 4$, upper plot) and the most central bin ($\langle N_{part} \rangle = 344 \pm 11$, lower plot) to a fit of proton-antiproton data (see text) scaled by $\langle N_{part}/2\rangle$. The dashed (solid) line shows the expection of $N_{coll}$ ($N_{part}$) scaling relative to $p+\bar{p}$ collisions. The brackets show the systematic uncertainty of the Au+Au data.
• Figure 3: Charged hadron yield in Au+Au in six centrality bins, divided by a fit to the most peripheral bin and by $\langle N_{part} /2 \rangle$. The dashed (solid) line shows the expectation for $N_{coll}$ ($N_{part}$) scaling relative to peripheral collisions. The brackets show the systematic uncertainty in the Au+Au data.
• Figure 4: Charged hadron yields per participant pair in 6 different transverse momentum bins, plotted as a function of $N_{part}$. The data are normalized to the yield in the most peripheral centrality bin. The dashed (solid) line shows the expectation for $N_{coll}$ ($N_{part}$) scaling from peripheral to central collisions. The brackets indicate the systematic uncertainty for the centrality evolution of this ratio (90% C.L.).