The rapidity dependence of the proton-to-pion ratio in Au+Au and p+p collisions at [formula omitted] and 200 GeV

Abstract

The BRAHMS measured proton-to-pion ratios in Au+Au and p+p collisions at s N N = 62.4 GeV and s N N = 200 GeV are presented as a function of transverse momentum and collision centrality within the pseudo-rapidity range 0 ⩽ η ⩽ 3.8 . The results for Au+Au at s N N = 200 GeV are compared with predictions from models which incorporate hydro-dynamics, hadron rescattering and jet production, in the η interval covered. In Au+Au collisions at s N N = 200 GeV , η ≈ 2.2 , and at s N N = 62.4 GeV , η = 0 , the bulk medium can be characterized by the common value of μ B ≈ 65 MeV . The p / π + ( p T ) ratios measured for these two selections display a striking agreement in the p T range covered (up to 2.2 GeV/c). At a collision energy of 62.4 GeV and at forward pseudo-rapidity we found a crossing point of p / π + ratios measured in central and semi-peripheral Au+Au and in p+p reactions. The crossing occurs in the narrow η bin around value of 3.2, simultaneously in the whole covered p T range ( 0.3 GeV/c < p T < 1.8 GeV/c ).