38 research outputs found
Strange Particle Production in p+p, p+Pb and Pb+Pb Interactions from NA49
Recent NA49 results on Lambda, Antilambda, Xi- and Antixi+ production in
minimum bias p+p and centrality selected p+Pb collisions at 158 GeV/c, and the
results on Lambda, Antilambda, K+ and K- production in central Pb+Pb collisions
at 40, 80 and 158 A GeV are discussed and compared with other available data.
By comparing the energy dependence of Lambda and Antilambda production at
mid-rapidity a striking similarity is observed between p+p and A+A data. This
is also seen in the energy dependence of the Lambda/pi ratio. K+/pi at
mid-rapidity is affected in a similar way, due to the associated production of
K+ together with Lambda particles. The observed yields increase faster than the
number of wounded nucleons when comparing p+Pb to p+p. As already observed in
A+A collisions, the increase is larger for multistrange than for strange
baryons and for baryons than for anti-baryons.Comment: 8 pages, 10 figures, To appear in proceedings of Strange Quark in
Matter 2001-A Flavourspace Odyssey, Frankfurt am Main, Germany, 24-29. Sept.
200
Chemical equilibrium study at SPS 158A GeV
A detailed study of chemical freeze-out in nucleus-nucleus collisions at beam
energy 158A GeV is presented. By analyzing hadronic multiplicities within the
statistical hadronization approach, the chemical equilibration of p-p, C-C,
Si-Si and Pb-Pb systems is studied as a function of the number of participating
nucleons in the system. Additionally, Two Component statistical hadronization
model is applied to the data and is found to be able to explain the observed
strangeness hadronic phase space under-saturation.Comment: 4 pages, 3 figures to appear in the proceedings of the ''Strangeness
in Quark Matter 2004'' conferenc
An Overview of Fluctuation and Correlation Results in Relativistic Heavy Ion Collisions
A great deal of recent data on event-by-event fluctuation and correlation
measurements has been released by several experiments at the SPS and RHIC.
Recent results on charge fluctuations, balance functions in pseudorapidity, and
average transverse momentum fluctuations will be reviewed. The results will be
compared to various model predictions after examining contributions to each
observable from known physics processes.Comment: 8 pages, 3 figures. Contribution to the Proceedings of the 17th
International Conference on Ultra Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2004), Oakland, California, 11-17 Jan 2004. Submitted to
J.Phys.
Strangeness and the discovery of quark-gluon plasma
Strangeness flavor yield s and the entropy yield S are the observables of the
deconfined quark-gluon state of matter which can be studied in the entire
available experimental energy range at AGS, SPS, RHIC, and, in near future, at
the LHC energy range. We present here a comprehensive analysis of strange, soft
hadron production as function of energy and reaction volume. We discuss the
physical properties of the final state and argue how evidence about the
primordial QGP emerges.Comment: 16 pages: Invited talk at 5th International Conference on Physics and
Astrophysics of Quark Gluon Plasma, February 8 - 12, 2005, Salt Lake City,
Kolkata, India, to appear in: Journal of Physics: Conference Serie
Relativistic Nucleus-Nucleus Collisions: from the BEVALAC to RHIC
I briefly describe the initial goals of relativistic nuclear collisions
research, focusing on the LBL Bevatron/Bevalac facility in the 1970's. An early
concept of high hadronic density fireball formation, and subsequent isentropic
decay (preserving information as to the high density stage) led to an outline
of physics observables that could determine the nuclear matter equation of
state at several times nuclear ground state matter density. With the advent of
QCD the goal of locating, and characterizing the hadron-parton deconfinement
phase transformation suggested the need for higher , the research
thus moving to the BNL AGS and CERN SPS, finally to RHIC at BNL. A set of
physics observables is discussed where present data span the entire
domain, from Bevalac and SIS at GSI, to top RHIC energy. Referring,
selectively, to data concerning bulk hadron production, the overall
evolution of directed and radial flow observables, and of pion pair
Bose-Einstein correlation are discussed. The hadronization process is studied
in the grand canonical statistical model. The resulting hadronization points in
the plane T vs. converge onto the parton-hadron phase boundary
predicted by finite lattice QCD, from top SPS to RHIC energy. At lower
SPS and top AGS energy a steep strangeness maximum occurs at which the
Wroblewski parameter 0.6; a possible connection to the QCD
critical point is discussed. Finally the unique new RHIC physics is addressed:
high hadron suppression and jet "tomography".Comment: 19 pages, 11 figure
QGP fireball explosion
We identify the major physics milestones in the development of strange
hadrons as an observable for both the formation of quark-gluon plasma, and of
the ensuing explosive disintegration of deconfined matter fireball formed in
relativistic heavy ion collisions at 160--20A GeV. We describe the physical
properties of QGP phase and show agreement with the expectations based on an
analysis of hadron abundances. We than also demonstrate that the m_t shape of
hadron spectra is in qualitative agreement with the sudden breakup of a
supercooled QGP fireball.Comment: 10 pages, incl. 4 figures J. Phys. G in press; presented at
STRANGENESS2000 International Conference, Berkeley July 200
Strangeness Report
The paper provides a short report on strangeness production in
ultrarelativistic nucleus-nucleus collision, with the main stress on strange
particle abundances.Comment: Proceedings of Quark Matter 200
Centrality and dE_{T}/d\etadN_{ch}/d\eta$ in Heavy Ion Collisions at Mid-Rapidity
The PHENIX experiment at RHIC has measured transverse energy and charged
particle multiplicity at mid-rapidity in Au + Au collisions at
= 19.6, 130, 62.4 and 200 GeV as a function of centrality. The presented
results are compared to measurements from other RHIC experiments, and
experiments at lower energies. The dependence of
and per pair of participants is consistent with logarithmic
scaling for the most central events. The centrality dependence of
and is similar at all measured incident
energies. At RHIC energies the ratio of transverse energy per charged particle
was found independent of centrality and growing slowly with . A
survey of comparisons between the data and available theoretical models is also
presented.Comment: Proccedings of the Workshop: Focus on Multiplcity at Bari, Italy,
June 17-19,2004. To be submitted to the Jornal of Physics, "Conference
series". Includes: 20 Pages, 15 figures, 3 Tables, 80 Referencie
Resonances and fluctuations of strange particle in 200 GeV Au-Au collisions
We perform an analysis of preliminary data on strange particles yields and
fluctuations within the Statistical hadronization model. We begin by describing
the theoretical disagreements between different statistical models currently on
the market. We then show how the simultaneous analysis of yields and
fluctuations can be used to differentiate between the different models, and
determine if one of them can be connected to underlying physics. We perform a
study on a RHIC 200 GeV data sample that includes stable particles, resonances,
and the event-by-event fluctuation of the ratio. We show that the
equilibrium statistical model can not describe the fluctuation, unless an
unrealistically small volume is assumed. Such small volume then makes it
impossible to describe the total particle multiplicity. The non-equilibrium
model,on the other hand, describes both the fluctuation and yields
acceptably due to the extra boost to the fluctuation provided by the high
pion chemical potential. and abundance is described
within error bars, but the is under-predicted to 1.5 standard
deviations. We suggest further measurements that have the potential to test the
non-equilibrium model, as well as gauge the effect of re-interactions between
hadronization and freeze-out.Comment: References added, equations corrected. As accepted for publication by
Journal of Physics
Strangeness and Quark Gluon Plasma
A brief summary of strangeness mile stones is followed by a chemical
non-equilibrium statistical hadronization analysis of strangeness results at
SPS and RHIC. Strange particle production in AA interactions at
\sqrt{s_{NN}}\ge 8.6 GeV can be understood consistently as originating from the
deconfined quark--gluon plasma in a sudden hadronization process. Onset of QGP
formation as function of energy is placed in the beam energy interval 10--30A
GeV/c. Strangeness anomalies at LHC are described.Comment: 30 pages including numerouse figures, tables. Opening Lecture:
Strangeness and Quark Gluon Plasma -- what has been learned so far and where
do we go at SQM2003, North Carolina, March 2003, submitted to J. Phys.