initial conditions and space-time scales in relativistic heavy ion collisions
DESCRIPTION
Initial conditions and space-time scales in relativistic heavy ion collisions. Yu. Sinyukov, BITP, Kiev (with participation of Yu. Karpenko, S.Akkelin). Expecting Stages of Evolution in Ultrarelativistic A+A collisions. t. “Soft Physics” measurements. A. x. t. Δω K. A. - PowerPoint PPT PresentationTRANSCRIPT
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Initial conditions and space-time scales in relativistic heavy ion
collisions
Yu. Sinyukov, BITP, Kiev(with participation of Yu. Karpenko, S.Akkelin)
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Expecting Stages of Evolution in Ultrarelativistic A+A collisions
t
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“Soft Physics” measurements
xt
A
A
ΔωK
p=(p1+ p2)/2
q= p1- p2
(QS) Correlation function
Space-time structure of the matter evolution, e.g.,
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Approximately conserved observables
APSD - Phase-space density averaged over some hypersurface , where all particles are already free and over momen- tum at fixed particle rapidity, y=0. (Bertsch)0. (Bertsch)
t
z
Chemical. f.-o.
Thermal f.-o.
APSD is conserved during isentropic and chemically frozen evolution (including a free streaming):
n(p) is single- , n(p1, p2 ) is double
(identical) particle spectra,
correlation function is C=n(p1, p2
)/n(p1)n(p2 ) p=(p1+ p2)/2
q= p1- p2
S. Akkelin, Yu.S. Phys.Rev. C 70 064901 (2004):
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The averaged phase-space density. LHC prediction = 0.2-0.3
Non-hadronic
DoF
Limiting HagedornTemperature
S. Akkelin, Yu.S: Phys.Rev. C 73, 034908 (2006); Nucl. Phys. A 774, 647 (2006)
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Energy dependence of the interferometry radii
Energy- and kt-dependence of the radii Rlong, Rside, and Rout for central Pb+Pb (Au+Au) collisions from AGS to RHIC experiments measured near midrapidity. S. Kniege et al. (The NA49 Collaboration), J. Phys. G30, S1073 (2004).
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HBT PUZZLE
The interferometry volume only slightly increases with collision energy (due to the long-radius growth) for the central collisions of the same nuclei.
Explanation:
only slightly increases and is saturated due to limiting Hagedorn temperature TH =Tc (B = 0).
grows with
A is fixed
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HBT PUZZLE & FLOWS
Possible increase of the interferometry volume with due to geometrical volume grows is mitigated by more intensive transverse flows at higher energies:
, is inverse of temperature
Why does the intensity of flow grow?
More more initial energy density more (max) pressure pmax
BUT the initial acceleration is ≈ the same
HBT puzzle Intensity of collective flows grow
Time of system expansion grows:
Initial flows (< 1-2 fm/c) develop
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Ro/Rs ratio and initial flows
M.Borysova, Yu.S., S.Akkelin, B.Erazmus, Iu.Karpenko,Phys.Rev. C 73, 024903 (2006)
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Developing of collective velocities in partonic matter at pre-thermal stage (Gyulassy, Karpenko, Yu.S., Nazarenko, BJP (2007)
Distribution function at initial hypersurface 0=1
Venagopulan, 2003, 2005; Kharzeev 2006
Equation for partonic free streaming:
Solution
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Transverse velocities at: =1 fm/c; Gaussian profile, R=4.3 fm
1st order phase transition
Crossover
IC at =0.1 (RHIC) and 0.07 (LHC) fm/c for Glasma from T. Lappy (2006)
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Equation of States
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Freeze-out hypersurface for LHC energies
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Yu.S. , Akkelin, Hama: Phys. Rev. Lett. 89 , 052301 (2002); + Karpenko: to be published
*Is related to local
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;• 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;• Calculation of “exact” DF and emission function; • Evaluation of spectra and correlations.
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Emission at RHIC top energy
EXTRA SLIDES
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Emission at LHC energy Sqrt(s) = 5.5 TeV
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Emission function at large pT
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Transv. spectra of pions (blue line is prediction)
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Long –radii for pions (blue line is prediction)
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Side- radii for pions (blue line is prediction)
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Out –radii for pions (blue line is prediction)
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Out-to-Side ratio for pions (blue line is prediction)
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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.
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