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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. Introduction. - PowerPoint PPT Presentation
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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
Introduction• * 1970 – JINR Dubna – first relativistic nuclear collisions using accelerator
systems – members of the Atomic and Nuclear Physics Chair were involved (Prof. C.Beşliu, Prof. N.Ghiordănescu) – studies related to the cumulative effect
• *’70’s – ’80’s – 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
• *’80’s – Ph.D. Thesis• ’90’s – 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
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 ’90’s• 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
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. Călin Beşliu (14), Prof. Alexandru Jipa (7))
• Institute of Nuclear Physics and Engineering – Applied Nuclear Physics Department, mainly
• University of Civil Marine Constanţa
• Different High Schools
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),
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
Results obtained in BRAHMS Collaboration
Kpnd,
RHIC experimentsRHIC experiments
Run 1: June - September 2000
First Physics Run
Au+Au @ two energies
SNN = 56 and 130 GeV
Two independent rings ~3.8 km in circumference
Run 2: July 2001- January 2002
Au+Au @ SNN = 200 GeV
(maximal design energy)
p+p (reference data)
Run 3: December 2002- May 2003
d+Au @ SNN = 200 GeV
p+p @ SNN = 200 GeV
Run 4: December 2003- May 2004
Au+Au @ SNN = 200 GeV; Au+Au @ SNN = 63 GeV; p+p@ SNN = 200 GeV
Run 5: December 2004- May 2005
Cu+Cu@ SNN = 200 GeV; p+p@ SNN = 200 GeV
RAA =Yield(AA)
NCOLL(AA) Yield(NN)
Scaled N+N reference
Nuclear Modification Factor
RAA<1 Suppression relative to scaled NN reference
Data do not show suppression Enhancement (RAA>1)
due to initial state multiple scattering (“Cronin effect”) Known in p+A collisions
High pt Suppression in Au+AuAt Mid-Rapidity (=0)
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.
d-Au Nuclear Modification factor at ~3.2
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
Central to peripheral ratio Rcp as a function of pseudorapidity measured by BRAHMS ford-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
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”
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 -1.5;+1.5 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 ….
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 plethoraof 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
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