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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

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t

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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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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. LHC 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)

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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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- 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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- 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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M.Borysova, Yu.S., S.Akkelin, B.Erazmus, Iu.Karpenko,

Phys.Rev. C 73, 024903 (2006)

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- Distribution function at initial hypersurface 0=1

Venagopulan, 2003, 2005; Kharzeev 2006

- Equation for partonic free streaming:

- Solution

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=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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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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- EXTRA SLIDES

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HIC at the LHC

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HIC at the LHC

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- 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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HIC at the LHC

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