60 research outputs found
Event-by-Event Fluctuations of Particle Ratios in Central Pb+Pb Collisions at 20 to 158 AGeV
In the vicinity of the QCD phase transition, critical fluctuations have been
predicted to lead to non-statistical fluctuations of particle ratios, depending
on the nature of the phase transition. Recent results of the NA49 energy scan
program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb
collisions at beam energies of 20-30 AGeV. This observation has been
interpreted as an indication of a phase transition at low SPS energies. We
present first results on event-by-event fluctuations of the kaon to pion and
proton to pion ratios at beam energies close to this maximum.Comment: 4 pages, 4 figures, Quark Matter 2004 proceeding
Results on correlations and fluctuations from NA49
The large acceptance and high momentum resolution as well as the significant
particle identification capabilities of the NA49 experiment at the CERN SPS
allow for a broad study of fluctuations and correlations in hadronic
interactions. In the first part recent results on event-by-event charge and p_t
fluctuations are presented. Charge fluctuations in central Pb+Pb reactions are
investigated at three different beam energies (40, 80, and 158 AGeV), while for
the p_t fluctuations the focus is put on the system size dependence at 158
AGeV. In the second part recent results on Bose Einstein correlations of h-h-
pairs in minimum bias Pb+Pb reactions at 40 and 158 AGeV, as well as of K+K+
and K-K- pairs in central Pb+Pb collisions at 158 AGeV are shown. Additionally,
other types of two particle correlations, namely pi p, Lambda p, and Lambda
Lambda correlations, have been measured by the NA49 experiment. Finally,
results on the energy and system size dependence of deuteron coalescence are
discussed.Comment: 10 pages, 12 figures, Presented at Quark Matter 2002, Nantes, France,
Corrected error in Eq.
Bose-Einstein Correlations of Charged Kaons in Central Pb+Pb Collisions at
Bose-Einstein correlations of charged kaons were measured near mid-rapidity
in central Pb+Pb collisions at 158 AGeV by the NA49 experiment at the
CERN SPS. Source radii were extracted using the Yano-Koonin-Podgoretsky and
Bertsch-Pratt parameterizations. The results are compared to published pion
data. The measured dependence for kaons and pions is consistent with
collective transverse expansion of the source and a freeze-out time of about
9.5 .Comment: 14 pages with 7 figures, submitted to Phys. Lett.
Cascade and anti-cascade production in central Pb+Pb collisions at 158 GeV/c per nucleon
Results of the production of Xi and Xi-bar hyperons in central Pb+Pb
interactions at 158 GeV/c per nucleon are presented. This analysis utilises a
global reconstruction procedure, which allows a measurement of 4pi integrated
yields to be made for the first time. Inverse slope paramters, which are
determined from an exponential fit to the transverse mass spectra, are shown.
Central rapidity densities are found to be 1.49 +- 0.08 and 0.33 +- 0.04 per
event per unit of rapidity for Xi and Xi-bar respectively. Yields integrated to
full phase space are 4.12 +- 0.02 and 0.77 +- 0.04 for Xi and Xi-bar. The ratio
of Xi-bar/Xi at mid-rapidity is 0.22 +- 0.03.Comment: 10 pages, 9 figure
Energy Dependence of and Production at CERN-SPS Energies
Rapidity distributions for and hyperons in central
Pb-Pb collisions at 40, 80 and 158 AGeV and for mesons
at 158 AGeV are presented. The lambda multiplicities are studied as a
function of collision energy together with AGS and RHIC measurements and
compared to model predictions. A different energy dependence of the
and is observed. The
ratio shows a steep increase with collision energy. Evidence for a
ratio greater than 1 is found at 40 AGeV.Comment: 6 pages, 9 figures, QM2002 proceedings, submitted to Nucl. Phys.
Recommended from our members
Selected problems in experimental intermediate energy. Progress report, February 1, 1994--January 31, 1997
A complete description of the research program of the intermediate energy group at the University of Houston may be found in previous progress reports, renewal proposals, and proposals to the various accelerator advisory committees. Recent documents are appended to this report and summaries of current research activities are presented in the next section. The objectives of the research program are to: (1) investigate selected, forefront problems in experimental intermediate energy physics; (2) educate students in this field of research; and, (3) develop the instrumentation necessary to undertake this experimental program. Generally, the research is designed to search for physical processes which cannot be explained by conventional models of elementary interactions. As one example, we use nuclear targets where the nucleus provides a many body environment of strongly interacting particles, and where one attempts to observe the perturbation of a known interaction by this environment. These effects, however, may be masked by the complexity of the many body problem and may be difficult to observe. Therefore, experiments of this type must be carefully chosen and analyzed for deviations from the more conventional models
Recommended from our members
Selected problems in experimental intermediate energy physics. Final technical report, February 1, 1991--January 31, 1994
A complete description of the research program of the intermediate energy group at the University of Houston may be found in previous progress reports, renewal proposals, and proposals to various accelerator advisory committees. The summaries of activities are presented in the next section. The objectives of the research program are to: (1) investigate selected, forefront problems in experimental intermediate energy physics; (2) educate students in this field of research; and (3) develop the instrumentation necessary to undertake this experimental program. There were three major thrusts of the program: (1) strange particle physics, where a strange quark is embedded in the nuclear medium; (2) muon electro-weak decay, which involves a search for a violation of the standard model of the electro-weak interaction; and (3) measurement of the spin dependent structure function of the neutron and proton
Recommended from our members
Selected problems in experimental intermediate energy physics
The objectives of this research program are to: investigate forefront problems in experimental intermediate energy physics; educate students in this field of research; and, develop the instrumentation necessary to undertake this experimental program. Generally, the research is designed to search for physical processes which cannot be explained by conventional models of elementary interactions. This includes the use of nuclear targets where the nucleus provides a many body environment of strongly perturbation of a known interaction by this environment. Unfortunately, such effects may be masked by the complexity of the many body problem and may be difficult to observe. Therefore, experiments must be carefully chosen and analyzed for deviations from the more conventional models. There were three major thrusts of the program; strange particle physics, where a strange quark is embedded in the nuclear medium; muon electro-weak decay, which involves a search for a violation of the standard model of the electro-weak interaction; and measurement of the spin dependent structure function of the neutron
Caesium dosing reduces uptake of radiocaesium by sheep
In sheep grazing pasture contaminated by radiocaesium, administration of stable caesium was found to inhibit the uptake of radiocaesium. Eight lambs feeding on a contaminated pasture received an oral dose of 500 mg CsCl and after 6 days had a radiocaesium load 17% lower than that of a control group on the same pasture. The rate of radiocaesium excretion from 4 lambs, in metabolism cages and fed uncontaminated grass, was unaffected by CsCl dosing in comparison with controls. Thus. caesium dosing appeared to inhibit uptake but did not alter rates of caesium loss by normal processes of metabolism. Measurements of stable and radioactive caesium excretion rates were interpreted using a compartment model, based on the hypothesis of two major caesium reservoirs within the sheep, with derived biological half-lives approximately 4 and 25 days, and capacities 20 and 80% of total, respectively. Caesium dosing appeared to saturate the latter reservoir and consequently inhibit further uptake. If a practicable method of application could be achieved, caesium dosing could be useful in the management of sheep and other grazing animals on radiocaesium-contaminated pasture and could find application to radiological protection in humans
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