Identified Baryon and Meson Distributions at Large Transverse Momenta fromAu+AuCollisions atsNN=200  

Abstract

Transverse momentum spectra of pi+/-, p, and p up to 12 GeV/c at midrapidity in centrality selected Au + Au collisions at square root sNN=200 GeV are presented. In central Au + Au collisions, both pi +/- and p(p) show significant suppression with respect to binary scaling at pT approximately >4 GeV/c. Protons and antiprotons are less suppressed than pi+/-, in the range 1.5 approximately < pT approximately < 6 GeV/c. The pi-/pi+ and p/p ratios show at most a weak pT dependence and no significant centrality dependence. The p/pi ratios in central Au + Au collisions approach the values in p + p and d + Au collisions at pT approximately >5 GeV/c. The results at high pT indicate that the partonic sources of pi+/-, p, and p have similar energy loss when traversing the nuclear medium.

Spectra of identified high-pTπ±andpAbelev1, Aggarwal2, Ahammed3 et al. 2010Phys. Rev. CSelf Cite283190View full textAdd to dashboardCite

“…For protons, the error ranges from 21% (at 3 GeV/c) to 23% (at 6 GeV/c). These uncertainties are similar to the earlier evaluation from Au + Au data analysis [9]. Systematic uncertainties from other possible sources such as the momentum resolution (studied by embedding) and the uncertainty in determination of the centroid position (within the particle identification procedure) are negligible.…”

“…Figure 2 shows π − /π + andp/p ratios in Cu + Cu data at √ s NN = 200 GeV for the four centrality bins. The data show no systematic trends versus centrality within uncertainties, and a weak (if any) decreasing p/p with transverse momentum (as observed in Au + Au collisions [9]). Thus, to improve the statistical uncertainties in the following discussion, data are averaged over particle charge.…”

“…We are utilizing the idea that the baryon to meson ratio is found higher in gluon jets compared to quark jets [8]. Identified proton and pion measurements from pp collisions concur with this picture [1,9], as well as direct measurements of baryon and meson production in quark and gluon jets [10]. Thus, identified particle measurements at high-p T can then be used to analyze gluon and quark propagation through the medium and to probe the color-charge differences of energy loss [2,9,11,12].…”

Production of π/K/p from intermediate to high pT

“…The proton-to-pion ratio increases from ≈ 0.38 to ≈ 0.8 going from peripheral (60-80%) to central (0-5%) Pb−Pb collisions at p T ≈ 3 GeV/c, then decreases to the value measured for vacuum fragmentation (pp collisions) for p T > 10 GeV/c. The result obtained for the most central collisions is similar to that measured at RHIC [10,11]. The kaon-to-pion ratio also exhibits a small bump around p T = 3 GeV/c.…”

Antimatter production in proton-proton and heavy-ion collisions at ultrarelativistic energies

“…3. The coalescence estimate was obtained using the p/p, / , /p, and /p ratios both measured by the STAR Collaboration [9,44,45] and obtained from the THERMUS calculations. We note that in the coalescence picture the equilibrium abundances of particle yields are not required.…”