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Searching Evidence for the Color Glass Condensate at RHIC. New Discoveries at RHIC BNL, May 14-15, 2004. J.-P. Blaizot and F. Gelis, SPhT, CEA Saclay and CNRS. Quantum ChromoDynamics. Non linear effects become important when. Gluon saturation
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Searching Evidence for the Color Glass Condensate at RHIC New Discoveries at RHIC BNL, May 14-15, 2004 J.-P. Blaizot and F. Gelis, SPhT, CEA Saclay and CNRS
QuantumChromoDynamics Non linear effects become important when
Gluon saturation a regime with weak coupling, many cooperating degrees of freedom, strong fields. Non linear effects important when Saturation scale Gribov, Levin, Ryskin 83 Mueller, Qiu 86
High density partonic systems Large occupation numbers Classical fields
The saturation scale From fit to DIS (HERA) In a nucleus The conditions in the central rapidity of a nucleus-nucleus collision at RHIC are similar to those at HERA
Early stages of a nucleus-nucleus collision Partons set free have typical tranverse momenta They are set free at (proper) time At that time (J.-P. B., A. Mueller, 87) Momentum distributions
NON LINEAR EVOLUTION EQUATIONS BALITSKY-KOVCHEGOV EQUATION COLOR GLASS CONDENSATE AND JIMWLK(*) EQUATION (*) Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov, Kovner
Geometrical scaling (Golec-Biernat,Kwiecinski,Stasto)
Numerical solution of the BK equation + DGLAP corrections (Gotsman, Levin, Lublinsky, Maor hep-ph/0209074)
PHOBOS Central Au+Au (200 GeV) 600 1200 Compilation by K. Eskola Total multiplicities
PHOBOS, PRL 87 Kharzeev & Levin, Phys. Lett. B523 (2001) 79
« Limiting fragmentation » PHOBOS, PRL 91 Interpretation in the color glass picture: J. Jalilian-Marian, nucl-th/0212018
y 0 0.05 0.1 0.2 0.4 0.6 1 1.4 2 Albacete et al, hep-ph/0307179 (Related analytical work by Iancu, Itakura, Triantafyllopoulos hep-ph/0403103)
- Saturation picture (color glass condensate) does provide a successful phenomenology, both at RHIC and at HERA. - Saturation manifests itself at lower energy in nucleus-nucleus collisions than in proton-proton collisions - Color glass only provides initial conditions. Because of final state interactions, AA collisions do not allow for direct tests. - dA are much better. Going to forward rapidity one gets a chance to « see » evolution of parton densities. - Phenomena should be more visible at the LHC
Why is it important to search for the color glass condensate ? • Saturation is a genuine, characteristic, QCD effect - Important to get a complete control of the initial conditions • May well turn into an essential piece in the chain of • arguments leading to the identification of the quark-gluon • plasma