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CERN Heavy Ion Forum
CERN Heavy Ion Forum on Transverse Thermalization
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TH Theory Conference Room (CERN)
TH Theory Conference Room
CERN
Description
1. "Early evolution of transversally thermalized partons"
by Wojciech Florkowski (INP Cracow & IF AS Kielce, Poland)
The idea that the parton system created in relativistic heavy-ion collisions (i) emerges in a state with transverse momenta close to thermodynamic equilibrium and (ii) its evolution at early times is dominated by the two- dimensional (transverse) hydrodynamics is investigated and shown to be consistent with data. It is argued that this mechanism may help to solve the HBT puzzle and the problem of early equilibration.
Our conclusions differ from those obtained earlier by Heinz and Wong. Apart from certain technical details, there are essentially two reasons for this discrepancy. Firstly, we assume that during the evolution the systems obeys the rules of truly two-dimensional thermodynamics. Secondly, we confront our results on v2 with the experimental data, whereas Heinz and Wong made a comparison with earlier three-dimensional hydrodynamic calculations.
2. "Elliptic flow from a transversally thermalized fireball"
Ulrich Heinz (CERN & Ohio State University)
The agreement of elliptic flow data at RHIC at central rapidity with the hydrodynamic model has led to the conclusion of very rapid thermalization. This conclusion is based on the intuitive argument that hydrodynamics, which assumes instantaneous local thermalization, produces the largest possible elliptic flow values and that the data seem to saturate this limit. In 2002, S.M.H. Wong and I investigated the question whether incompletely thermalized viscous systems may actually produce more elliptic flow than ideal hydrodynamics. Motivated by the extremely fast primordial longitudinal expansion of the reaction zone, we studied a toy model which exhibits thermalization only in the transverse directions but undergoes collisionless free-streaming expansion in the longitudinal direction. For collisions at RHIC energies, elliptic flow results from the model were compared with those from hydrodynamics. Our important conclusion, believed to be generic, was that, with the final particle yield and k_T-distribution fixed, the transversally thermalized model was not able to produce the measured amount of elliptic flow. I will report on this work, point out differences with the recent paper by Bialas, Chojnacki and Florkowski who come to different conclusions, and also tie our 2002 result to recent findings that viscous hydrodynamics generically produces less elliptic flow than ideal fluid dynamics.
More information: http://aliceinfo.cern.ch/static/HIF/welcome.html
by Wojciech Florkowski (INP Cracow & IF AS Kielce, Poland)
The idea that the parton system created in relativistic heavy-ion collisions (i) emerges in a state with transverse momenta close to thermodynamic equilibrium and (ii) its evolution at early times is dominated by the two- dimensional (transverse) hydrodynamics is investigated and shown to be consistent with data. It is argued that this mechanism may help to solve the HBT puzzle and the problem of early equilibration.
Our conclusions differ from those obtained earlier by Heinz and Wong. Apart from certain technical details, there are essentially two reasons for this discrepancy. Firstly, we assume that during the evolution the systems obeys the rules of truly two-dimensional thermodynamics. Secondly, we confront our results on v2 with the experimental data, whereas Heinz and Wong made a comparison with earlier three-dimensional hydrodynamic calculations.
2. "Elliptic flow from a transversally thermalized fireball"
Ulrich Heinz (CERN & Ohio State University)
The agreement of elliptic flow data at RHIC at central rapidity with the hydrodynamic model has led to the conclusion of very rapid thermalization. This conclusion is based on the intuitive argument that hydrodynamics, which assumes instantaneous local thermalization, produces the largest possible elliptic flow values and that the data seem to saturate this limit. In 2002, S.M.H. Wong and I investigated the question whether incompletely thermalized viscous systems may actually produce more elliptic flow than ideal hydrodynamics. Motivated by the extremely fast primordial longitudinal expansion of the reaction zone, we studied a toy model which exhibits thermalization only in the transverse directions but undergoes collisionless free-streaming expansion in the longitudinal direction. For collisions at RHIC energies, elliptic flow results from the model were compared with those from hydrodynamics. Our important conclusion, believed to be generic, was that, with the final particle yield and k_T-distribution fixed, the transversally thermalized model was not able to produce the measured amount of elliptic flow. I will report on this work, point out differences with the recent paper by Bialas, Chojnacki and Florkowski who come to different conclusions, and also tie our 2002 result to recent findings that viscous hydrodynamics generically produces less elliptic flow than ideal fluid dynamics.
More information: http://aliceinfo.cern.ch/static/HIF/welcome.html
Organised by
François Arleo, Yiota Foka and Urs Achim Wiedemann
