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Initial conditions and space-time scales in relativistic heavy ion collisions

Initial conditions and space-time scales in relativistic heavy ion collisions Yu. Sinyukov, BITP, Kiev (with participation of Y. Karpenko, A. Nazarenko) Expecting Stages of Evolution in Ultrarelativistic A+A collisions t Relatively small space-time scales (HBT puzzle) 10-15 fm/c

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Initial conditions and space-time scales in relativistic heavy ion collisions

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  1. Initial conditions and space-time scales in relativistic heavy ion collisions Yu. Sinyukov, BITP, Kiev (with participation of Y. Karpenko, A. Nazarenko) Quark Matter 2008

  2. Expecting Stages of Evolution in Ultrarelativistic A+A collisions t Relatively small space-time scales (HBT puzzle) 10-15 fm/c Early thermal freeze-out: T_th Tch 150 MeV 7-8 fm/c Elliptic flows 1-3 fm/c Early thermalization at 0.5 fm/c 0.2?(LHC) Quark Matter 2008

  3. Basic ideas for the early stage Yu.S. Acta Phys.Polon. B37 (2006) 3343; Gyulassy, Yu.S., Karpenko, Nazarenko Braz.J.Phys. 37 (2007) 1031; Akkelin, Yu.S., Karpenko arXiv:0706.4066 (see also in “Heavy Ion Collisions at the LHC - Last Call for Predictions”). At free streaming Hydrodynamic expansion: gradient pressure acts So, even if : and Free streaming: Gradient of density leads to non-zero collective velocities For nonrelativistic (massive) gas Quark Matter 2008

  4. Basic ideas for the late stage Yu.S., Akkelin, Hama: Phys. Rev. Lett. 89, 052301 (2002); + Karpenko: to be published; Akkelin, Yu.S., Karpenko arXiv:0706.4066 Hydro-kinetic approach Continuous emission t • is based on combination of Boltsmann equation and for hydro relativistic finite expanding system; • provides evaluation of escape probabili- ties and deviations (even strong) of distri-bution functions from local equilibrium; • accounts for conservation laws at the particle emission; PROVIDE earlier (as compare to CF-prescription) emission of hadrons, because escape probability accounts for whole particle trajectory in rapidly expanding surrounding (no mean-free pass criterion for freeze-out) x Y. Hama and collaborators Quark Matter 2008

  5. Distribution function at initial hypersurface Distribution function motivated by CGC effective FT Quark Matter 2008 T. Lappi, R. Venugopalan, Phys. Rev. C74 (2006) 054905

  6. Developing of collective velocities in partonic matter at pre-thermalstage (Yu.S. 2006) • Equation for partonic free streaming in hyperbolic coordinates: • Solution where Quark Matter 2008

  7. Flows from non-equilibrated stage (at proper time = 1 fm/c) |v| in approximation for initial Gauss elliptic profile Quark Matter 2008

  8. Comparision of flows at free streaming and hydro evolution Quark Matter 2008

  9. Energy profile. even being isotropic at becomes anisotropic at =1 fm/c. Supposing fast thermalization near this time, we use prescription Quark Matter 2008

  10. Equation of States Quark Matter 2008

  11. Transverse velocities at: =1fm/c; Gaussian profile, R=4.3 fm IC at 0=0.1 (RHIC) and 0.07(LHC) fm/c for Glasma from T. Lappy (2006) 1st order phase transition RHIC Crossover LHC Quark Matter 2008

  12. Yu.S. , Akkelin, Hama: Phys. Rev. Lett. 89 , 052301 (2002); + Karpenko: to be published Hydro-kinetic approach • MODEL • is based on relaxation time approximation for relativistic finite expanding system; • provides evaluation of escape probabilities and deviations (even strong) • of distribution functions [DF] from local equilibrium; • 3. accounts for conservation laws at the particle emission; • Complete algorithm includes: • solution of equations of ideal hydro [THANKS to T. Hirano for possibility to use code] ; • calculation of non-equilibrium DF and emission function in first approximation; • solution of equations for ideal hydro with non-zero left-hand-side that • accounts for conservation laws for non-equlibrated process of the system • which radiated free particles during expansion; • [Corresponding hydro-code (2007): Tytarenko,Karpenko,Yu.S.(to be publ.)] • Calculation of “exact” DF and emission function; • Evaluation of spectra and correlations. Is related to local * Quark Matter 2008

  13. Rate of collisions for pions in expanding hadron gas depending on T and p It accounts (in the way used in UrQMD) for pion cross sections with 360 hadron and resonance species with masses < 3 GeV. It is supposed that gas is in chemical equilibrium at Tch = 175 MeV and then is expanding. The decay of resonances into expanding liquid is taken into account. Quark Matter 2008

  14. Emission at RHIC top energy [PCE and FS initial stage] [Modified PCE-Hirano and FS initial stage] • EXTRA SLIDES Quark Matter 2008

  15. Emission at LHC energy Sqrt(s) = 5.5 TeV [PCE and FS initial stage] Quark Matter 2008

  16. Transv. spectra of pions (blue line is prediction) Quark Matter 2008

  17. Long –radii for pions(blue line is prediction) Quark Matter 2008

  18. Side- radii for pions(blue line is prediction) Quark Matter 2008

  19. Out –radii for pions(blue line is prediction) Quark Matter 2008

  20. Out-to-Side ratio for pions (blue line is prediction) Quark Matter 2008

  21. Emission densities for fixed pt=0.3 GeV/c EoS accounts for crossover (Laine&Schroder) and CFO with resonance decays. Preliminary Quark Matter 2008

  22. Emission densities for fixed pt=0.6 GeV/c EoS accounts for crossover (Laine&Schroder) and CFO with resonance decays. Preliminary Quark Matter 2008

  23. Emission densities for fixed pt=1.2 GeV/c EoS accounts for crossover (Laine&Schroder) and CFO with resonance decays. Preliminary Quark Matter 2008

  24. HBT long-radius in CGC approach, with EoS accounting for crossover (Laine&Schroder) and CFO with resonance decays. Preliminary Quark Matter 2008

  25. Conclusions • The relatively small increase of interferometry radii with energy, as compare with expectations, are caused by • increase of transverse flow due to longer expansion time; • developing of initial flows at early pre-thermal stage; • more hard transition EoS, corresponding to cross-over; • non-flat initial (energy) density distributions, similar to Gaussan; • early (as compare to CF-prescription) emission of hadrons, because escape probability account for whole particle trajectory in rapidly expanding surrounding (no mean-free pass criterion for freeze-out) • The hydrokinetic approach to A+A collisions is proposed. It allows one to describe the continuous particle emission from a hot and dense finite system, expanding hydrodynamically into vacuum, in the way which is consistent with Boltzmann equations and conservation laws, and accounts also for the opacity effects. Quark Matter 2008

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