Transparency, Mixing and Reflection in Relativistic NucleusNucleus Collisions

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Transparency, Mixing and Reflection in
Relativistic Nucleus-Nucleus
Collisions
Mark Gorenstein
BITP, Kiev and FIAS, Frankfurt
hep-ph/0511058, Gazdzicki and M.G.
Phys. Rev. C73 (2006) HSD and UrQMD
Konchakovski, M.G., Bratkovskaya et al
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Participants and Spectators in AA Collisions
Centrality Trigger Transparency and Mixing in
AA Baryon Number Fluctuations Hadron
Multiplicity Fluctuations Projectile and Target
Hemispheres Role of Acceptance
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Scaled variance
Nucleons participants and spectators.
Pb-Pb 158 AGeV
NA49 Measured by ZDC
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Gazdzicki and M.G. hep-ph/0511058
T
M
R
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Bonus
NA49 at SPS a dedicated facility to study
event-by-event fluctuations in nuclear collisions
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HSD is close to T-models for baryon flows
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Independent Sources Number of Sources is
Proportional to Number of Participants
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HSD is close to T-models for pion sources
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(1.1 ltylt 2.6) (-2.6ltylt-1.1)
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Conclusions
Study of fluctuations gives a unique possibility
to investigate the early stage dynamics of
initial flows The existing models are divided
into 3 limiting groups T-, M-, R- models HSD
and UrQMD are close to T-models NA49 data for
charged hadron multiplicity fluctuations are
consistent with M-models
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Scaled variances
AntibaryonsBaryons Total
?
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ch

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Conclusions

• The fluctuations of the number of target
  participants strongly influence the baryon number
  and charged multiplicity fluctuations
• The consequences depend crucially on the
  mixing-transparency effects
• Because of their too much transparency the HSD
  and UrQMD transport models cannot reproduce the
  NA49 results on multiplicity fluctuations
• The fluctuations in the projectile and target
  hemisphere tell us about mixing. The centrality
  dependence of the fluctuations is needed.
• The fluctuations of the baryon number and
  electric charge in different acceptance are
  important
• Pure statistical fluctuations could be seen in
  most central collisions with Np 2A