Speaker
Prof.
Jean-Yves Ollitrault
(Institut de Physique Theorique - CEA Saclay)
Description
Hydrodynamical models have generally failed to describe interferometry radii
measured at RHIC. In order to investigate this "HBT puzzle",
we carry out a systematic study of HBT radii in ultrarelativistic
heavy-ion collisions within a two-dimensional transport model.
We compute the out and side radii as a function of the transverse
momentum for various values of the Knudsen number, which measures the
degree of thermalization in the system.
In the case of central collisions, we show that the large difference
between the side and out radii, which is seen in hydrodynamical models
but not in data (HBT puzzle), appears only for unrealistically small
values of the Knudsen number. For realistic values of the Knudsen
number, our result for the ratio Ro/Rs is much closer to data than
standard hydrodynamical results.
The transverse momentum dependence of the radii, which is usually said
to reflect collective flow, also has a very limited sensitivity to the
degree of thermalization.
Finally, we study the azimuthal oscillations of Ro, Rs, and R_{os}
for non central collisions. Their amplitudes depend very little on the
Knudsen number. In particular, the azimuthal dependence of Rs is found
to reflect the initial eccentricity of the overlap area.
Author
Prof.
Jean-Yves Ollitrault
(Institut de Physique Theorique - CEA Saclay)
