Kaon and Lambda Production at Intermediate pₜ: Insights into the Hadronization of the Bulk Partonic Matter Created in Au+Au Collisions at RHIC

الأصل · EN

Measurements of identified particles over a broad pₜ range may provide strong evidence for the existence of a thermalized partonic state in heavy-ion collisions (i.e. a quark-gluon plasma). Of particular interest are the centrality dependence and the azimuthal anisotropy in the yield of baryons and mesons at intermediate pₜ. The first measurements of v₂ and the number-of-binary-collisions scaled centrality ratio RCP for Kₛ⁰ and Λ+Λ production in Au+Au collisions at RHIC are presented. These measurements from the STAR detector establish the particle-type dependence of v₂ and RCP within 0.4 < pₜ < 6.0. At intermediate pₜ (1.5--4.5 GeV/c) v₂ of Kₛ⁰ and Λ+Λ is shown to follow a number-of-constituent-quark scaling with v₂kaon(pₜ/2)/2 = v₂lambda(pₜ/3)/3. RCP shows that lambda production at intermediate pₜ increases more rapidly with system size than kaon production: consistent with multi-parton dynamics in particle production. At pₜ = 5.5 GeV/c lambda, kaon, and charged hadron production are suppressed by a similar factor (RCP ≈ 0.33): establishing the extent of the centrality dependent baryon enhancement. The particle- and pₜ-dependence of v₂, and RCP are consistent with expectations based on hadronization of bulk partonic matter by coalescence. As such, the constituent-quark-number scaled v₂ may reflect the anisotropy established in a partonic stage providing strong evidence for the existence of a quark-gluon plasma in Au+Au collisions at RHIC.