Computer simulation of particle production in hydrokinetic approach to A A collisions

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Computer simulation of particle production in
hydrokinetic approach to AA collisions

• S.V Akkelin1, Y. Hama2, Iu.A.Karpenko1, Yu.M.
  Sinyukov1
• 1Bogolyubov Institute for Theoretical Physics
• 2University of Sao Paulo
• work in progress

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Relativistic hydrodynamics
Hydrodynamic equations
Ideal fluid
EoS pp(e) ICs
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Hydrokinetic approach
Ideal hydro
IC EoS
Relaxation time approximation
analytics
Setting
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Models

• Toy model relativistic massive Boltzmann gas
  of pions
• More realistic model QGP crossover phase
  transition hadron-resonance gas

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Toy model Initial conditions

• Chemically equilibrated pion gas at
• Collective velocities
• Energy density profile Woods-Saxon, Au
• Temperature in the cental plateau

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Toy model

• HYDRO
• Chemically frozen evolution in
• EoS for chem. frozen massive pion gas

Useful parametrization

• KINETICS
• Cross section

(ideal hydro expansion)

• Collision rates according to cross section

Relaxation time
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Results, 400mb case

• Pion emission function integrated over d2p
  (pT01.5 GeV)
• at z0, pz0

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Results, 400mb case
The same one, 3D view
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Results, 40mb case
Pion emission function integrated over d2p
(pT01.5 GeV) at z0, pz0
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Results, 40mb case
The same, 3D view
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Escaping in different directions
More cross section
More opacity
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Freeze-out hypersurfaces
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Pion spectra from the toy model
CFp at T110 MeV escape w 400mb Teff200 MeV
Escape w 40mb Teff235 MeV
Lower scattering rate(bigger relaxation time)
Higher effective temperature
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Interferometry radii
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A More Realistic Model

• ICs
• ICs energy density (T.Hirano, K.Tsuda, Phys.
  Rev. C 66, 054905, used for 130 GeV AuAu RHIC
  and 17 GeV PbPb SPS energies)

• Corresponding initial temperature

• All the initial chemical potentials are zero

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A More Realistic Model EoS

• Equation of state is taken from
• PT calculations for QGP (M. Laine, Y.Shröder),
  nf3 caseZero chemical potentials
• Hadron-resonance gas below Tc.(H. Bebie, P.
  Gerber, J. L. Goity, and H. Leutwyler, Nucl.
  Phys. B378, 95, 1992 used by T. Hirano et al.)
• The switching between these EoS is performed.

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EoS pressure temperature
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EoS closer look
The switching
Switching temperature Tsw156 MeV, corresponds to
e0.325 GeV/fm3
No 1st-order phase transition
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Details of kinetics

• Cross section Linear growth from 60mb (HG
  phase) to 250mb (QGP phase)
• Can choose any large enough s in QGP

• ?1 for HG phase
• ?0 for QGP (no hadrons)

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A More Realistic Model Results
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Different pT

• More low-pT particles are emitted from the
  center at the late times
• More high-pT particles are emitted from the QGP
  boundary at early times

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A More Realistic Model Spectra
Continuous emission ?Teff190 MeV CFp at 110 MeV
? Teff175 MeV
Escape process
Higher effective temperature
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Interferometry radii
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Conclusions

• The calculations within the first approximation
  to hydro-kinetic approach is performed in two
  particular models.
• The effective temperature of (pion) spectra is
  increased in a case of early emission.
• Ro/Rs ratio can decrease in hydro-kinetic model
  as compared with standard Landau/Cooper-Frye
  approach.
• There is strong x-p correlation particles with
  higher momenta are emitted earlier from the
  periphery of the system. There are different
  effective freeze-outs for different pT.
• Emission region is rather wide (not approximated
  by sharp freeze-out hypersurface).

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• THANK YOU
• for your attention