Transverse hydrodynamics with sudden hadronization: production of strangeness

W Florkowski (1, 2) , R Ryblewski (2)

1 Institute of Physics
2 The H. Niewodniczański Institute of Nuclear Physics

We consider a physical scenario for ultra-relativistic heavy-ion collisions where, at the early stage, only transverse degrees of freedom of partons are thermalized, while the longitudinal motion is described by free streaming. When the energy density of the partonic system drops to a certain critical value, the partons hadronize and the newly formed hadronic system freezes out. This sudden change is described with the help of the Landau matching conditions followed by the simulations done with THERMINATOR. The proposed scenario reproduces well the transverse-momentum spectra, the elliptic flow coefficient v 2, and the HBT radii of pions and kaons studied at RHIC (Au+Au collisions at √ s NN = 200 GeV). It also reproduces quite well the transverse-momentum spectra of hyperons. The spacetime evolution of matter produced in the ultra-relativistic heavy-ion collisions is described most successfully by the perfect-fluid hydrodynamics [ 1, 2, 3 ]. With the initial conditions inferred from the Glauber model, the hydrodynamic approach describes very well the hadron transverse-momentum spectra and the elliptic flow coefficient v 2. With the Gaussian initial conditions, the hydrodynamic approach describes also the HBT radii [ 4 ]. Unfortunately, the use of the hydrodynamics is still challenged by the problem of early thermalization - the correct description of the data requires an early initialization time for hydrodynamics [ 5 ], which implicitly assumes a very early equilibration time. A possible solution to this problem was suggested in Ref. [ 6 ], where the idea was proposed that only transverse degrees of freedom are thermalized, while the longitudinal motion is described by free streaming (a physical picture explained naturally in the string models [ 7, 8]). In this framework, called below the transverse hydrodynamics, one can obtain the parton transverse-momentum spectra and v 2 which are consistent with the data [ 6, 9 ]. In this paper we generalize this approach by inclusion of the sudden-hadronization transition modeled with the help of the Monte Carlo code THERMINATOR [ 12 ].

Mots clés: 25.75.-q; 25.75.Dw; 25.75.Ld

W Florkowski, R Ryblewski. Transverse hydrodynamics with sudden hadronization: production of strangeness. Journal of Physics G: Nuclear and Particle Physics, 2010, 37 (9), pp.94023. ⟨10.1088/0954-3899/37/9/094023⟩. ⟨hal-00600842⟩