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Initial conditions and space-time scales in relativistic heavy ion collisionsPowerPoint Presentation

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

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

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

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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)

Heavy Ion Collisions at the LHC

Last Call for Predictions

Expecting Stages of Evolution in Ultrarelativistic A+A collisions

t

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“Soft Physics” measurements collisions

A

x

t

ΔωK

A

(QS) Correlation function

Space-time structure of the

matter evolution, e.g.,

p=(p1+ p2)/2

q= p1- p2

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Approximately conserved observables collisions

t

Thermal f.-o.

- 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)

Chemical. f.-o.

n(p) is single- , n(p1, p2 ) is double (identical) particle spectra,

correlation function is C=n(p1, p2)/n(p1)n(p2)

z

p=(p1+ p2)/2

q= p1- p2

- APSD is conserved during isentropic and chemically frozen evolution (including a free streaming):

S. Akkelin, Yu.S. Phys.Rev. C 70 064901 (2004):

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The averaged phase-space density. collisionsLHC prediction = 0.2-0.3

Non-hadronic

DoF

Limiting

Hagedorn

Temperature

S. Akkelin, Yu.S: Phys.Rev. C 73, 034908 (2006);

Nucl. Phys. A 774, 647(2006)

HIC at the LHC

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Energy dependence of the interferometry radii collisions

Energy- and kt-dependence of the radii Rlong, Rside, and Rout forcentral Pb+Pb(Au+Au) collisions from AGS to RHICexperiments measurednear midrapidity. S. Kniege et al. (The NA49 Collaboration), J. Phys. G30, S1073 (2004).

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HBT PUZZLE collisions

- 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 collisions

- 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 collisions

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-thermalstage (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: pre-thermal

=1fm/c; Gaussian profile, R=4.3 fm

IC at =0.1 (RHIC) and 0.07(LHC) fm/c for Glasma from T. Lappy (2006)

1st order phase transition

Crossover

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Yu pre-thermal.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;
- 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.

Is related to local

*

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Transv. spectra of pions (blue line is prediction) pre-thermal

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Out-to-Side ratio for pions (blue line is prediction) pre-thermal

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Conclusions pre-thermal

- 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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