Nuclear
Physics Colloquium
Location: Physics
Building Science Campus Riedberg, Max-von-Laue-Str. 1, room PHYS
2.116
Time: Thursday, October 24, 2013, 4:30-5:30pm (plus
10min for discussion)
Contact: hees@fias.uni-frankfurt.de
Onset of
hydrodynamical behavior in heavy ion collisions
Thomas Epelbaum (CEA)
The
heavy ion collisions performed at the RHIC and the LHC are among the
most impressive experimental achievements ever performed in physics. In
those two rings, heavy ions (lead, gold...) are smashed onto one another
at a speed that almost reaches the one of light. The analysis performed
on the products of these collisions are of great interest for
understanding Quantum Chromodynamics (QCD) at very high energies.
During
the past ten years or so, the RHIC and the LHC have more or less
established a striking feature of the collision products. These latters
– referred as the Quark Gluon Plasma, or QGP – seem to behave like a
nearly perfect fluid, and do so after a very short transient time: less
than 1 fm/c. This is assumed to be the case, because relativistic
hydrodynamics with a very small value of shear viscosity has been such a
successful theory to describe the experimental data. In the meantime,
theoretical models based on QCD have so far failed to predict such a
hydrodynamical behavior. The one that we will come to use – the Color
Glass Condensate (CGC) effective theory – even predict at its Leading
Order (LO) a negative longitudinal pressure of the system at the initial
time, with a value opposite to the energy density and the transverse
pressure. By contrast, hydrodynamics has among its postulates a small
anisotropy of the system. This apparent paradox between theory and
experiment has yet to receive a satisfying answer. Improvements of the
CGC are therefore needed.
We
will report here recent analytical and numerical progress performed
within this CGC framework, showing in particular that an early
isotropization of the system is possible.
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Physics Colloquium Homepage