14 research outputs found
Rapidity and transverse momentum dependence of pion-pion Bose-Einstein correlations measured at 20, 30, 40, 80, and 158 AGeV beam energy
Preliminary results on pion-pion Bose-Einstein correlations in central Pb+Pb collisions measured by the NA49 experiment are presented. Rapidity as well as transverse momentum dependence of the HBT-radii are shown for collisions at 20, 30, 40, 80, and 158 AGeV beam energy. Including results from AGS and RHIC experiments only a weak energy dependence of the radii is observed. Based on hydrodynamical models parameters like lifetime and geometrical radius of the source are derived from the dependence of the radii on transverse momentum
Energy Dependence of π−π−Bose-Einstein-Correlations in Central Heavy Ion Collisions measured by the Experiment NA49)
Um Signaturen für die Erzeugung eines Quark-Gluon Plasmas zu untersuchen, wurden im Rahmen eines Energie-Scan Programmes mit dem Experiment NA49 am CERN-SPS Beschleunigerring bei 5 unterschiedlichen Strahlenergien Schwerionenkollisionen untersucht. Eine Möglichkeit, Informationen über die raum-zeitliche Struktur einer solchen Kollision zu erhalten, ist durch die Untersuchung von Bose-Einstein-Korrelationen gegeben. Die Untersuchung der Energieabhängigkeit dieser Korrelationen ist Gegenstand dieser Arbeit. Um die Dynamik der Kollisionen zu studieren, wird die Analyse für die einzelnen Energien in Abhängigkeit des mittleren transversalen Impulses und der Paarrapidität durchgeführt. In der Arbeit werden zunächst die theoretischen Grundlagen zur Untersuchung von Schwerionenkollisionen mit Hilfe von Bose-Einstein-Korrelationen erarbeitet. Nach einer kurzen Darstellung des Experimentes NA49 folgt eine detaillierte Beschreibung der Datenselektion und der verwendeten Analyse-Methode. Die Ergebnisse werden im Rahmen eines Modells zur Beschreibung einer Teilchenquelle interpretiert
Modification of jet-like correlations in Pb-Au at the SPS
A high statistics study of high- two-particle azimuthal correlations in
Pb-Au at GeV, performed by the CERES experiment at the
CERN-SPS, is presented. A broad away-side correlation with significant dip at
is observed. The shape and magnitude of the correlation
is similar to measurements at RHIC. In comparison to PYTHIA calculations, we
observe a significant excess of soft particles at the away-side. A study of
charge correlations between trigger and associated particles disfavors vacuum
fragmentation of the away-side jet and suggests significant energy transfer of
the hard-scattered parton to the medium.Comment: Proceedings to Quark Matter 2009 Conference, Knoxville, Tennessee,
US
Two- and three-particle azimuthal correlations of high-pt charged hadrons in Pb-Au collisions at 158A GeV/c
Azimuthal correlations of hadrons with high transverse momenta serve as a
measure to study the energy loss and the fragmentation pattern of jets emerging
from hard parton-parton interactions in heavy ion collisions. Preliminary
results from the CERES experiment on two- and three-particle correlations in
central Pb-Au collisions are presented. A strongly non-Gaussian shape on the
away-side of the two-particle correlation function is observed, indicating
significant interactions of the emerging partons with the medium. Mechanisms
like deflection of the initial partons or the evolution of a mach cone in the
medium can lead to similar modifications of the jet structure on the away-side.
An analysis based on three-particle correlations is presented which helps to
shed light on the origin of the observed away-side pattern.Comment: 4 pages, 2 figures, contribution to the Quark Matter conference 200
Evidence for an exotic S=-2, Q=-2 baryon resonance in proton-proton collisions at the CERN SPS
Results of resonance searches in the Xi - pi -, Xi - pi +, Xi -bar+ pi -, and Xi -bar+ pi + invariant mass spectra in proton-proton collisions at sqrt[s]=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi - pi - baryon resonance with mass of 1.862±0.002 GeV/c2 and width below the detector resolution of about 0.018 GeV/c2. The significance is estimated to be above 4.2 sigma . This state is a candidate for the hypothetical exotic Xi --3/2 baryon with S=-2, I=3 / 2, and a quark content of (dsdsu-bar). At the same mass, a peak is observed in the Xi - pi + spectrum which is a candidate for the Xi 03/2 member of this isospin quartet with a quark content of (dsusd-bar). The corresponding antibaryon spectra also show enhancements at the same invariant mass
System size and centrality dependence of the balance function in A + A collisions at sqrt s NN = 17.2 GeV
Electric charge correlations were studied for p+p, C+C, Si+Si and centrality selected Pb+Pb collisions at sqrt s_NN = 17.2$ GeV with the NA49 large acceptance detector at the CERN-SPS. In particular, long range pseudo-rapidity correlations of oppositely charged particles were measured using the Balance Function method. The width of the Balance Function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions
System size and centrality dependence of the balance function in A+A collisions at sqrt[sNN]=17.2 GeV
Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at sqrt[sNN]=17.2 GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions
Two- and three-particle azimuthal correlations of high-pt charged hadrons in Pb+Au collisions at 158 GeV per nucleon
Ein wesentliches Ziel der Physik mit schweren Ionen ist die Untersuchung der Zustände von Kernmaterie bei hohen Dichten bzw. Temperaturen. Solche Zustände lassen sich durch Kollisionen von hochenergetischen schweren Ionen in Teilchenbeschleunigern wie dem Super Proton Synchrotron SPS am Europäischen Kernforschungszentrum CERN in Genf erzeugen und untersuchen. Die vorliegende Arbeit beschäftigt sich mit der Analyse des Einflusses des in einer solchen Kollision erzeugten Mediums auf hochenergetische Teilchen, welche dieses Medium durchqueren. Hierzu werden Korrelationen zwischen Teilchen mit hohem Transversalimpuls pt als Funktion der Zentralität der Kollisionen und der Ladung der beteiligten Teilchen untersucht. Ziel ist es, hierdurch eine experimentelle Grundlage für die theoretische Beschreibung der Eigenschaften des Mediums in solchen Kollisionen bereitzustellen. ..