Physics%20at%20NICA:%20the%20view%20from%20LPI%20RAS

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NICA round table III 06.11.08
Physics at NICA the view from LPI RAS
A.V. Leonidov
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• Big goals
• Qualitative and quantitative description of
  deconfined
• matter and associated features of multiparticle
  production
• Description of the features of particle
  production related
• to dense strongly interacting medium present
• in nucleus-nucleus collisions and not present
  in
• proton-proton and proton-nucleus ones.

• Remarks on elementary particle source its
  generalization
• on high density case.
• Rescattering of elementary sources and
  transverse and
• longitudinal spectra in pA and AB collisions.
• Event-by-event fluctuations of transverse
  momenta
• Is the produced dense strongly interacting
• matter homogeneous on the event-by-event basis?

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• Gross features of multiparticle production at
  moderate energies
• such as transverse spectra and particle yields
  equivalent in

and

• Transverse spectra are of thermal form with a
  temperature
• T160-200 MeV.

• Same value as a coefficient in the Hagedorn
  spectrum

• Simplified description hadronic string with
  hand-made
• rules for its breaking and creation of
  transverse momentum

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Quantitative picture
D. Kharzeev, K. Tuchin (2005) P. Castorina, D.
Kharzeev, H. Satz (2007)

• Fundamental mechanism of particle production is
• a Hawking-Unruh radiation through the
  confinement
• horizon an interface between open color and
  hidden
• phases.
• Based on close relations between Unruh radiation
  and
• Schwinger pair creation mechanism
• Particle production through quantum tunneling

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A fundamental challenge for theory is a
generalization of the PKS approach to dense
deconfined sources and description of their
coexistence with hidden color hadronic phase.
At NICA energies a quark-junction matter?
Gluon strings in baryons structured as a
junction (have a Mercedes form)
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Rescattering and transverse and longitudinal
spectra in pA and AB collisions
A.L., M. Nardi, H. Satz (1997)
Particle spectrum of a fireball at rest
Particle spectrum of a moving fireball
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Multiparticle production proceeds through
creation of a string of elementary sources
shifted in transverse direction due to
rescattering
cluster distribution function in longitudinal
and transverse rapidity
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Longitudinal cluster distribution
Works quite well for AB collisions at SPS
energies for protons and pions
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Pion and nucleon rapidity spectra, Au-Au
collisions
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Cluster distribution in transverse rapidity
Distribution width controlled by
fixed by reproducing pA transverse spectra
number of rescatterings
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Pion and nucleon transverse momentum spectra,
Au-Au collisions
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• Reproduces pion and proton transverse spectra
• in pA and AB collisions at SPS energies very
  well
• with T150 MeV.
• Problems with kaon transverse spectra
• Are the kaon spectra anomalous already at pA
  level?
• Arent we we putting in some flow by hand by
  using
• the random walk in transverse rapidity? Random
  walk
• in transverse momentum looks more natural from
• the point of view of Regge phenomenology.

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Event-by-event fluctuations in transverse momentum
A.L., M. Gazdzicki, G. Roland (1999)
Measure of event-by event fluctuations
and
calculated in LNZ approach too large at SPS
energies in nuclear collisions

• Value of

calcula

• Fluctuation patterns are much more sensitive to
  genuine
• nucleus-nucleus phenomena than spectra
• What is an event-by-event pattern in transverse
  momentum
• fluctuations in pA ?

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Is the produced dense strongly interacting matter
homogeneous on the event-by-event basis?
Early stage of high energy nuclear collisions is
inevitably inhomogeneous on the event-by-event
basis due to deconfined degrees of freedom.
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M. Guylassy, D. Rischke, B. Zhang (1997)

• Such a hot-spot structure means that transverse
  energy density is
• random
• strongly correlated

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Event-by-event versus averaging
Inclusive averaging can be dangerous!
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M. Kirakosyan, A.L. (2008)
Energy loss spraying of WW proper field modes
(e.g. of a constituent quark) due to their
interaction with the medium gt medium-induced
radiative loss
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Main challenge
Realistic microscopic description of domains of
deconfined dense strongly interacting matter
as created in nuclear collision and its
incorporation in the MC generators