Speaker
Description
The thermalized QCD matter formed in heavy-ion collisions is tilted in the reaction plane as a function of rapidity, while the production profile of partons from hard scatterings is symmetric in rapidity [1]. This leads to a rapidity-odd directed flow (v1) for high-pT hadrons and can provide valuable constraints on the initial longitudinal distribution of the fireball as well as the path length-dependent energy loss of partons. Hydrodynamic models suggest that the double sign change of v1 slope (dv1/dy) at midrapidity for net baryon as a function of beam energy is a signature of the first-order phase transition [2]. The light nuclei and strange hadrons might be more sensitive to the early EoS because of their heavy masses and smaller hadronic interaction cross section, respectively. Due to the different sensitivity of strange particles to hadronic phases, the mass ordering of elliptic flow (v2) is expected to be violated between proton and φ meson in the low-pT range (pT <1.5 GeV/c) [3].
In this talk, we will present the new precise v1 measurement of π, K, p and φ in Au+Au collisions at sNN = 27, 54.4 GeV and deuteron at sNN = 7.7 to 39 GeV. The first measurement of pseudorapidity and centrality dependence of the v1 of high-pT (>5 GeV/c) charged hadrons in Au+Au collisions at sNN = 54.4 and 200 GeV will be presented. The v2 of identified hadrons (π, K, p, φ, KS0 , Λ, Ξ, Ω) in Au+Au collisions at √sNN = 54.4 GeV will also be presented. These results will be compared to model calculations and the physics implications will be discussed.
Referene :
[1] P. Bozek, I. Wyskiel, Phys. Rev. C. 81, 054902 (2010); A. Adil, M. Gyulassy, Phys. Rev. C. 72, 034907 (2005).
[2] D. H. Rischke et al, arXiv:nucl-th/9505014 (1995); H. St¨ocker, Nucl. Phys. A 750, 121 (2005).
[3] T. Hirano et al., Phys. Rev. C 77, 044909 (2008); S. Takeuchi et al., Phys. Rev. C 92, 044907 (2015).
