Scaling properties of proton and anti-proton production in s(NN)**(1/2) = 200-GeV Au + Au collisions.

The PHENIX collaboration
Adler, S.S. , Afanasiev, S. , Aidala, C. , Ajitanand, N.N. , Akiba, Y. , Alexander, J. , Amirikas, R. , Aphecetche, L. , Aronson, S.H. , Averbeck, R.
Phys.Rev.Lett. 91 (2003) 172301, 2003.

Abstract (data abstract)
We report on the yield of protons and anti-protons, as a function of centrality and transverse momentum, in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured at mid-rapidity by the PHENIX experiment at RHIC. In central collisions at intermediate transverse momenta (1.5 < $p_T$ < 4.5 GeV/$c$) a significant fraction of all produced particles are protons and anti-protons. They show a centrality-scaling behavior different from that of pions. The $\bar{p}$/$\pi$ and $p$/$\pi$ ratios are enhanced compared to peripheral Au+Au, $p$+$p$, and $e^+$$e^-$ collisions. This enhancement is limited to $p_T$ < 5 GeV/$c$ as deduced from the ratio of charged hadrons to $\pi^0$ measured in the range 1.5 < $p_T$ < 9 GeV/c.

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