A'N'Sissakian, A'S'Sorin

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Physics Program
A.N.Sissakian, A.S.Sorin
Round Table Discussion II Searching for the mixed
phase of strongly interacting matter at the JINR
Nuclotron Nuclotron facility development JINR,
Dubna, October 6 7, 2006
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AGS
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NUCLOTRON JINR
Project parameters maximum energy 5 GeV/nucl.
for nuclei with ? 200.
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PHASE DIAGRAMS
Y.B.Ivanov, V.N.Russkikh, V.D.Toneev, Phys. Rev.
C73 044904 (2006)
For central collisions at the Nuclotron energy
even if an average state of the whole strongly
interacting system does not approach the mixed
phase, an essential part of the system volume
will spend a certain time in the mixed phase.
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http//theor.jinr.ru/meetings/2005/roundtable/

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Phases of strongly interacting matter
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Nuclotron
http//www.gsi.de/
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FAIR GSI
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Nuclotron
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Nuclotron facility development

• Accelerator/experiment options under discussion
• 1. Synchrotron with a beam energy of up to 10
  AGeV, beam intensity of Au/Pb/U ions more than
  106/s, internal fixed target.
• 2. Collider with c.m. energy of ?sNN 7 GeV
  (equivalent to a fixed target energy of about 24
  AGeV) and luminosity of 1027cm-2 s-1
  (corresponding to a reaction rate of 6 kHz for Au
  beams).

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Required parameters   The following basic
initial parameters have been accepted in
designing physical installation   -        
Kinetic energy of each colliding beam 2.5 A
GeV -         The setup covers solid angle close
to 4? -         Average
luminosity of colliding beams 1?1027
cm-2?s-1. -         Total cross section of heavy
ion interaction (UU) 7 b -         The mean
multiplicity of charged particles in a central
collision 600 -         Fraction of central
collisions 5 -         Fraction of events
with strange particles 6 -         Fraction
of events with lepton pairs in domain of ?
meson 10-4   The following interaction rate
characterizes the setup capability   - Frequency
of interaction 7?103 /s -         Total
number of interactions per year assuming the
statistics is being collected for 50 of the
calendar time 1?1011 -         A number of
central interactions per year 5?109 -        
A number of central interactions with strange
particles per year 3?108 -         A number of
central interactions with lepton pairs in the
domain of ? meson per year 5?105   From
these estimations it is possible to conclude that
luminosity 1027 cm-2?s-1 may be sufficient for
the decision of the above form
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From the accelerator hand of the project the
scheme I differs from schemes II and III mainly
in one point only scheme I presumes the
construction of two new storage rings operating
at a fixed magnetic field, schemes II and III
require creation of a new synchrotron of maximum
energy of 10 GeV/u. The price of two storage
rings is comparable with the cost of a new
synchrotron. New linear injector for the
Nuclotron may have the same structure and price
for all the schemes if EBIS ion source is
applied.   Owing to wider experimental
possibilities preference is given the collider
version of the new facility and this scheme is
described in the project.  
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The collider option permits to scan a larger
region of the QCD phase diagram, and is
preferable with respect to the fixed target
option.
The project has to be realized within 5-6 years
in order to be operational well before the FAIR
project. This boundary condition limits the size
of the project and restricts the technology of
the accelerator and of the experimental setup to
available solutions.
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http//theor.jinr.ru/meetings/2006/roundtable/
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• The NICA project is dedicated to the design and
  construction at JINR of a new relativistic
  heavy-ion superconducting collider based on the
  Nuclotron accelerator complex.
• General goal of the project is to start in the
  coming 5?6 years experimental study of hot and
  dense strongly interacting QCD matter and search
  for possible manifestation of signs of the mixed
  phase and critical endpoint in heavy ion
  collisions. The MPD is proposed for these goals.
• Additionally, as a result of the project
  realisation, the potentials of the Nuclotron
  accelerator complex will be sufficiently
  increased in all the fields of its current
  physics program and the facility creation will
  open new fields of experimental studies.
• The project realization presumes fulfilment of
  the following tasks
• - Upgrade of the Nuclotron and reaching its
  design parameters,
• - Development of highly charged heavy ion
  sources,
• - Creation of a new linear injector,
• Creation of two new superconducting storage rings
  to provide collider experiment with heavy ions
  like Au or U at energy 2.5 x 2.5 GeV/u
  (equivalent fixed target energy is 24 GeV/u )
  with average luminosity of 1027 cm-2?s-1 if
  magnetic rigidity of the collider rings is chosen
  to be equal to the Nuclotron project one, the
  maximum experiment energy reaches 5 x 5 GeV/u
  (equivalent fixed target energy is 70 GeV/u ).
• There are two versions of the collider and
  detector projects. In the first collider version,
  one of the new storage rings will be used as an
  ion beam accumulator at intermediate energy that
  permits generation of intensive beams of
  completely stripped heavy ions and then provides
  acceleration in the Nuclotron up to maximum
  energy of 5?6 GeV/u (depending on the Z/A ratio)
  for fixed target experiments.
• The project of a new linear injector allows also
  an effective acceleration of light ions to
  Nuclotron injection energy in order to increase
  intensity of polarized ion beams.

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The physics program
1. The nuclear matter equation-of-state at high
densities. 2. In-medium properties of hadrons.
3. Space-time evolution of nuclear
interaction. 4. The first order deconfinement
and/or chiral symmetry restoration phase
transitions. 5. The QCD critical endpoint.
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 Future heavy-ion experiments in the beam energy
range between 2 and 24 AGeV 1. Multistrange
hyperons. The yields, spectra and collective flow
of (multi) strange hyperons are expected to
provide information on the early and dense phase
of the collision as they are produced close to
threshold. Therefore, these particles are
promising probes of the nuclear matter
equation-of-state at high baryon density. 2.
Event-by-event fluctuations. The hadron yields
and momenta should be analyzed event-wise in
order to search for nonstatistical fluctuations
which are predicted to occur in the vicinity of
the critical endpoint and when penetrating the
coexistence phase of the first order
deconfinement and/or chiral phase transition. In
order to subtract the (dominant) contributions
from resonance decays one should measure the
yields of the relevant short-lived particles such
as the f and the K mesons. 3. HBT
correlations. Measurement of short correlations
between hadrons p, K, p, ? allows one to
estimate the space-time size of a system formed
in nucleus-nucleus interactions. Alongside with
the increase of fluctuations, the spatial size of
the system is expected to be getting smaller near
the deconfinement phase transition due to
softening of the equation of state (the softest
point effect).
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 4. Penetrating probes. Measurements of dilepton
pairs make it possible to investigate in-medium
spectral functions of low-mass vector mesons
which are expected to be noticeably modified due
to effects of chiral symmetry restoration in
dense and hot matter. (Note that for dilepton
production processes there is an suppression by
3-4 orders of magnitude. For average luminosity
of colliding beams 1027 cm-2 s-1 a number of
central interactions with lepton pairs in the
domain of rho-meson is 105-106 per year,
assuming the statistics is being collected for
50 of the calendar time). Specific properties of
the sigma-meson as a chiral partner of pions,
which characterizes a degree of chiral symmetry
violation, may be in principle detected near the
phase boundary via a particular channel of
sigma-decay into dileptons or correlated
gamma-gamma pairs. Above a beam energy of about
15 AGeV also charmonium might be detectable.
J/Psi mesons are a promising probe for the
deconfinement phase transition (needs additional
consideration).  5. Open charm (above 15 AGeV).
D-mesons probe the early phase of the collision
and are sensitive to in-medium effects due to
chiral symmetry restoration. Alongside with a low
yield these mesons have some particularities in
their detection what should be considered later
in more details. Possibly it is a good task when
higher colliding energy will be reached.
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Experiments at AGS have studied hadron production
(p, K, p, ?) in AuAu collisions at beam
energies between 2 and 10 AGeV. At 6 AGeV also ?
hyperons have been observed. Event-by-event
fluctuations have not been analysed. No dilepton
data have been measured. Therefore, new
experiments in this energy range should
concentrate on the excitation function of
(multi)strange hyperons and on event-by-event
observables.
In the beam energy range between 10 and 20 AGeV
no collision experiments with beams of heavy
nuclei have been performed. Therefore, the
collider option offers the unique opportunity to
perform pioneering experiments which should
measure all hadrons including multi-strange
hyperons, their phase-space distributions and
collective flow. This includes also
event-by-event observables.
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Theoretical (model and lattice) predictions for
the location of the critical end-point. Points
are calculated in different models specified in
M. Stephanov, Int. J. Mod. Phys. A20, 4387
(2005)hep-ph/0402115.
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Conclusions

• A study of the phase diagram in the domain
  populated by heavy-ion
• collisions with the bombarding energy 5
  24 GeV/nucleon to search for the mixed phase
  seems to be a very attractive task.
• 2. The use of the isospin asymmetry as an
  additional conserving parameter to characterize
  the created hot and dense system attracts new
  interest in this problem (critical end-boundary
  hypersurface ? ).
• 3. The available theoretical predictions are
  strongly model dependent giving rather dispersive
  results. There are no lattice QCD predictions for
  this highly nonpertubative region. Much
  theoretical work should be done and only future
  experiments may disentangle these models.
• A JINR Nuclotron possibility of accelerating
  heavy ions to the project energy of 5A GeV and
  increasing it up to 24A GeV can be realized in 5
  - 6 years. This will enable us to effort a unique
  opportunity for scanning heavy-ion interactions
  in energy, centrality and isospin asymmetry. It
  seems to be optimal to have the gold and uranium
  beams in order to scan in isospin asymmetry in
  both central and semi-central collisions at not
  so high temperatures.

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THANK YOU FOR ATTENTION!