文档介绍：Pion Entropy and Phase Space Density at RHIC
John G. Cramer Department of Physics University of Washington, Seattle, WA, USA
Second Warsaw Meeting on Particle Correlations and Resonances in Heavy Ion Collisions Warsaw University of Technology
October 16, 2003
Phase Space Density: Definition & Expectations
Phase Space Density - The phase space density f(p,x) plays a fundamental role in quantum statistical mechanics. The local phase space density is the number of pions occupying the phase space cell at (p,x) with 6-dimensional volume Dp3Dx3 = h3.
The source-averaged phase space density is áf(p)ñ º ∫[f(p,x)]2 d3x / ∫f(p,x) d3x, ., the local phase space density averaged over the f-weighted source volume. Because of Liouville’s Theorem, for free-streaming particles áf(p)ñ is a conserved Lorentz scalar.
At RHIC, with about the same HBT source size as at the CERN SPS but with more emitted pions, we expect an increase in the pion phase space density over that observed at the SPS.
October 16, 2003
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John G. Cramer
hep-ph/0212302
Entropy: Calculation & Expectations
Entropy – The pion entropy per particle Sp/Np and the total pion entropy at midrapidity dSp/dy can be calculated from áf(p)ñ. The entropy S of a colliding heavy ion system should be produced mainly during the parton phase and should grow only slowly as the system expands and cools.
Entropy is conserved during hydrodynamic expansion and free-streaming. Thus, the entropy of the system after freeze-out should be close to the initial entropy and should provide a critical constraint on the early-stage processes of the system.
nucl-th/0104023
A quark-gluon plasma has a large number of degrees of freedom. It should generate a relatively large entropy density, up to 12 to 16 times larger than that of a hadronic gas.
At RHIC, if a QGP phase grows with centrality we would expect the entropy to grow strongly with increasing centrality and participant number.
Can Entropy provide the QGP “Smoking Gun”??
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