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or little Big Bang

Equilibration of Matter Near QCD Critical Point L.Bravina,I.Arsene,M.S.Nilsson, K.Tywoniuk,E.Zabrodin(Oslo University). or little Big Bang. ICHEP’06, Moscow University, 27.07.2006. Content.

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or little Big Bang

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  1. Equilibration of Matter Near QCD Critical Point L.Bravina,I.Arsene,M.S.Nilsson, K.Tywoniuk,E.Zabrodin(Oslo University) or little Big Bang ICHEP’06, Moscow University, 27.07.2006

  2. Content Motivation. Why 40 AGeV? Conditions of thermal and chemical equilibrium Statistical model of an ideal hadron gas Relaxation to equilibrium in central cell EOS of hot and dense matter in the cell Summary and perspectivesotoivation

  3. Motivation Why 40 AGeV?

  4. Equation of State Tricritical point is located around 10-40 GeV (LQCD) We have to explore this energy range to study the possible phase transition QGP can be formed already at low energies H. Stoecker, nucl-th/0506013 L. Bravina et al., PRC 60 (1999) 024904; 63 (2001) 064902

  5. Experimental Indications Onset of deconfinement or transition from baryon to meson dominated matter? M. Gazdzicki, nucl-th/0512034 J. Cleymans et al., hep-ph/0510283

  6. Central cell: Relaxation to equilibrium

  7. Equilibration in the Central Cell Kinetic equilibrium: Isotropy of velocity distributions Isotropy of pressure Thermal equilibrium: Energy spectra of particles are described by Boltzmann distribution Chemical equlibrium:Particle yields are reproduced by SM with the same values of

  8. Statistical model of ideal hadron gas input values output values Multiplicity Energy Pressure Entropy density

  9. Pre-equilibrium Stage Homogeneity of baryon matter Absence of flow The local equilibrium in the central zone is quite possible

  10. Kinetic Equilibrium Isotropy of velocity distributions Isotropy of pressure Velocity distributions and pressure become isotropic at t=9 fm/c (for 40 AGeV)

  11. Thermal and Chemical Equilibrium Evolution of yields Energy spectra Thermal and chemical equilibrium seems to be reached

  12. Negative net strangeness density Net strangeness density in the central cell at 11 to 80 AGeV Net strangeness in the cell is negative because of different interaction cross sections for Kaons and antiKaons with Baryons

  13. Equation of State T vs. energy, etc

  14. Isentropic expansion Expansion proceeds isentropically (with constant entropy per baryon). This result supports application of hydrodynamics

  15. EOS in the cell energy vs. baryon density temperature vs. energy Beginning of temperature ”saturation” (but no limiting Hagedorn temperature yet) Dense and hot equilibrated matter is formed

  16. How dense can be the medium? “Small” cell (V => 0) ”Big” cell (V = 5x5x5 fm^3) Dramatic differences at the non-equilibrium stage; after beginning of kinetic equilibrium the energy densities and the baryon densities are the same for ”small” and ”big” cell

  17. EOS in the cell pressure vs. energy sound velocity

  18. Modification of analysis (small cells)

  19. EOS in the cell temperature vs. baryo-chemical potential S.Ejiri et al., S. Ejiri et al., PRD 73 (2006) 054506 The “knee” is similar to that in 2-flavor lattice QCD

  20. Fixed vs. non-fixed cell At energies below 40 AGeV isentropic expansion starts much earlier The kink is seen at all energies and deserves further study

  21. Fixed vs. non-fixed cell pressure vs. energy (fixed cell) non-fixed cell In this plot no deviations from the straight-line are observed

  22. Summary and perspectives • There is a kinetic equilibrium stage of hadron-string matter in the central cell at t > 8 fm/c • The ratio P/e is approximately constant and equals 0.12 (AGS), 0.14 (40 AGeV), and 0.15 (SPS & RHIC) => onset of saturation • Entropy per baryon ratio remains constant during the time interval 8 fm/c < t < 20 fm/c. This supports application of hydrodynamics • Temperature vs. chemical potential: the knee structure which appears at the onset of equilibrium should be studied further

  23. Energy dependence of suppression for particle production in pA collisions Nuclear modification factors for pA collisions are compared for a large range of energies. Interplay of energy-mom conservation and shadowing at low pT. Cronin at pT > 2 GeV. Expect suppression for pT > 2 GeV at LHC due to gluon shadowing!

  24. Energy dependence of suppression for particle production in pA collisions Amount of shadowing is consistent with the Glauber-Gribov approach. Suppression factor for RHIC should be bigger compared to SPS at all pT. Arsene, Bravina, Kaidalov, Tywoniuk, Zabrodin

  25. Back-up slides: Anisotropic flow

  26. Elliptic flow of pions and protons at 40 AGeV Significant dip at midrapidity for proton flow in central events C. Alt et al. (NA49), PRC 68 (2003) 034903

  27. Elliptic flow of pions and protons at 40 AGeV However, the dip at midrapidity disappears if one uses the {2} or {4} cumulant method C. Alt et al. (NA49), PRC 68 (2003) 034903

  28. Elliptic flow of pions and protons at 40 AGeV

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