Research%20in%20Relativistic%20Nuclear%20Physics%20at%20the%20Faculty%20of%20Physics%20of%20the%20University%20of%20Bucharest

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Research in Relativistic Nuclear Physics at the
Faculty of Physics of the University of Bucharest

• Alexandru JIPA
• Atomic and Nuclear Physics Department, Faculty of
  Physics, University of Bucharest, ROMANIA

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Introduction

• 1970 JINR Dubna first relativistic nuclear
  collisions using accelerator systems members of
  the Atomic and Nuclear Physics Chair were
  involved (Prof. C.Besliu, Prof. N.Ghiordanescu)
  studies related to the cumulative effect
• 70s 80s many Diploma Thesis in
  Relativistic Nuclear Physics related to the
  results obtained in symmetric and asymmetric
  nucleus-nucleus collisions at 4.5 A GeV/c SKM
  200 Collaboration, mainly
• 80s Ph.D. Thesis
• 90s Relativistic Nuclear Physics course
  students specialized in Nuclear and Particle
  Physics
• 1996-present - Master studies in Nuclear and
  Particle Physics 3 semesters 3 courses
  Relativistic Nuclear Physics, Anomal States and
  Phase Transitions in Nuclear Matter, Processing
  of the Information at Complex experimental
  set-ups
• 3 Diploma Theses, 3 Master Theses, 1 Ph.D.
  Theses per academic year with subjects from
  Relativistic Nuclear Physics

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International Collaborations

• Direct involving
• SKM 200 Collaboration (JINR Dubna)
• MARUSYA Collaboration (JINR Dubna)
• BRAHMS Collaboration (BNL Upton, New York)
• NA50 Collaboration (CERN Geneva) only at the
  beginning of 90s
• Indirect involving
• ALICE (CERN Geneva) Ph.D. students, members of
  different Romanian research institutes
• ATLAS (CERN Geneva) Ph.D. students, members of
  different Romanian research institutes
• CMS (CERN Geneva) Ph.D. students, members of
  different Romanian research institutes
• BECQUEREL Collaboration (JINR Dubna) - Ph.D.
  students, members of different Romanian research
  institutes

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National Collaborations

• Institute of Space Sciences many students have
  a job and excellent conditions to continue their
  works in the filed also, they are to possibility
  to work for Ph.D. Thesis (Advisors Prof. Calin
  Besliu (14), Prof. Alexandru Jipa (7))
• Institute of Nuclear Physics and Engineering
  Applied Nuclear Physics Department, mainly
• University of Civil Marine Constanta
• Different High Schools

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Main research studies and results

• Global characterization of He-A_T, C-A_T, O-A_T,
  Ne-A_T collisions at 4.5 A GeV/c (multiplicities,
  participants, momentum spectra, cross sections)
• Inverse slopes for pions (temperatures), baryonic
  chemical potential, baryonic and energy densities
• Space-time characterization of the particle
  source, correlations in the particle source
  (fireball)
• Investigations for thermal equilibration in
  fireball, hydrodynamic flow (global analysis
  jets of nuclear matter),

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Main research studies and results (2)

• Transverse momentum - longitudinal momentum
  correlations (connections with anomal states
  cumulative effect)
• Behaviour of the antiparticle to particle ratios
  for stopped charged particles in streamer chamber
• Some evidences for the influence of the nuclear
  medium on the particle properties (modification
  of the rest mass with the increase of the
  density)
• Studies on intermittent behaviour

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Results obtained in BRAHMS Collaboration
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RHIC experiments

• Run 1 June - September 2000
• First Physics Run
• AuAu _at_ two energies
• ?SNN 56 and 130 GeV

• Run 2 July 2001- January 2002
• AuAu _at_ ?SNN 200 GeV
• (maximal design energy)
• pp (reference data)

• Run 3 December 2002- May 2003
• dAu _at_ ?SNN 200 GeV
• pp _at_ ?SNN 200 GeV

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• Run 4 December 2003- May 2004
• AuAu _at_ ?SNN 200 GeV AuAu _at_ ?SNN 63
  GeV pp_at_ ?SNN 200 GeV
• Run 5 December 2004- May 2005
• CuCu_at_ ?SNN 200 GeV pp_at_ ?SNN 200 GeV

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• Data do not show suppression
• Enhancement (RAAgt1)
• due to initial state multiple
• scattering (Cronin effect)
• Known in pA collisions

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High pt Suppression in AuAu
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d-Au, ?sNN 200 GeV
Charged particle multiplicities for the
centrality ranges of 0-30 and 30-60. The
square points and circular points from SiMA and
TMA detectors, respectively, while the triangles
are from the BBC detectors.
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d-Au Nuclear Modification factor at ? 3.2
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Evolution of the nuclear modification factor
measured by BRAHMS for the 10 most central d-Au
collisions at sqrt(s_NN) 200 GeV, as o function
of pseudorapidity
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Central to peripheral ratio Rcp as a function of
pseudorapidity measured by BRAHMS for d-Au
collisions at the RHIC top energy (central to
peripheral, semi-central to peripheral)

• In central collisions increased Cronin effect
  
• additional suppression at forward rapidities
  suppression mechanism that scales
• with the collision centrality
• Colour Glass Condensate
• pQCD and string breaking for soft coherent
  particle production

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The difference between positive and negative
hadrons in dAu at 4 degrees
This measured difference (2 at 3GeV/c) is not
easily explained if pion production is dominant.
(NLO pQCD) It has been early dubbed as beam
fragmentation
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• The experimental results from BRAHMS RHIC are
  consistent with formation of a hot dense system
  that
• Exhibits a high degree of reaction transparency
  leading to the formation of a near baryon free
  central region
• There is an appreciable energy loss of the
  colliding nuclei, so the conditions for the
  formation of a very high energy density zone with
  approximate balance between matter and antimatter
  in a rapidity interval of -1.51.5 around
  mid-rapidity are present
• There are indications that the initial energy
  density is considerable large, so it is difficult
  to consider that the hadrons are isolated and
  well defined entities
• Relative abundances of different particles
  suggest chemical equilibrium at a temperature
  around 175 MeV
• Small values of the chemical potential are
  observed
• General conditions for formation of a deconfined
  system of quarks and gluons appear, but .

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other features defining the quark-gluon plasma
are absent or are not been identified up to now
(vanishing interactions between quarks,
characteristics of the chiral symmetry
restoration, clear phase transition behaviour of
the system
Main questions The properties of the matter
as it is created in high energy nucleus-nucleus
collisions clearly bears the imprint of a system
characterized by quark and gluon degree of
freedom over a range larger than the
characteristic dimensions of the nucleon? The
color change is effective at distances larger
than those of conventional confined objects?
(high p_T suppression could be a such candidate,
but there are some problems the magnitude of
the observed effect can not be reproduce)
There is no doubt that the experiments at RHIC
have revealed a plethora of new phenomena for the
most part have come as a surprise. In this sense
it is clear that the matter that is created at
RHIC differs from anything that has been seen
before. What name to give it must await our
deeper understanding of this matter White paper
of the BRAHMS Collaboration
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Other Romanian physicists participating in
BRAHMS Dr. Dan Argintaru, Dr. Florin Constantin,
Dr. Daniel Felea, Asist.Prof.Dr.Marius Calin,
Ciprian Mitu, Mihai Potlog, Silvia Ochesanu,
Costin Caramarcu Dr. Rory Clarke postdoc Other
Ph.D. students and Master Students involved in
the researches in the Relativistic Nuclear
Physics field Claudian Grigorie, Ileana Stefan,
Bogdan Iliescu, Amelia Horbuniev, Cristian
Bordeianu, Valentin Grossu, Madalin Cherciu,
Tiberiu Esanu, Rodica Dinu