부산대학교 도서관

We report measurements of the ratios of identified hadrons (π, K, p, Λ) in Au+Au collisions at $$ as a function of both collision centrality and transverse momentum (p_T). Ratios of anti-baryon to baryon yields are independent of p_T within 2 < p_T < 6 GeV/c indicating that, for such a range, our measurements are inconsistent with theoretical pQCD calculations predicting a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, a strong baryon enhancement relative to meson yields is observed as a function of collision centrality in this intermediate p_T region, leading to p/π and Λ/K ratios greater than unity. The nuclear modification factor, R_cp (central relative to peripheral collisions), is used to illustrate the interplay between jet quenching and hadron production. The physics implications of these measurements are discussed with reference to different theoretical models (Fries et al 2003 Phys. Rev. C 68 044902; Gyulassy et al 2001 Phys. Rev. Lett. 86 2537; Greco et al 2003 Phys. Rev. C 68 034904).