We report on recent data of e+e− pair emission in proton nucleus collisions at energies above the light vector meson production thresholds. Invariant mass distributions for the p+Nb system at Ekin ...3.5 GeV are compared to data from elementary p+p reactions at the same beam energy. We observe a constant π0/ω yield ratio for both systems but an excess in the mass region above the π0 mass. Furthermore we present here the normalization procedure that was applied to p+Nb collisions by measuring the production of negative pions in the HADES acceptance.
The High Acceptance DiElectron Spectrometer HADES has been recently commissioned at GSI, Darmstadt. It has been designed for systematic studies of hadron properties inside nuclear matter. We report ...first preliminary results on invariant masses e
+e
--pairs which were measured in
12C +
12C collisions at
E
kin
=
2
GeV
⋅
A
. The analysis methods are briefly outlined and a comparison with detailed Monte-Carlo simulations is shown.
We present the transverse momentum spectra and rapidity distributions of {pi}{sup -} and K{sub S}{sup 0} in Ar + KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the High ...Acceptance Di-Electron Spectrometer (HADES). The reconstructed K{sub S}{sup 0} sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental {pi}{sup -} and K{sub S}{sup 0} distributions to predictions by the Isospin Quantum Molecular Dynamics (IQMD) model. The model calculations show that K{sub S}{sup 0} at low transverse momenta constitute a particularly well-suited tool to investigate the kaon in-medium potential. Our K{sub S}{sup 0} data suggest a strong repulsive in-medium K{sup 0} potential of about 40 MeV strength.
The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega! ...invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.
We report first results on a deep subthreshold production of the doubly strange hyperon Xi- in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High ...Acceptance Di-Electron Spectrometer at SIS18/GSI. A high-statistics and high-purity Lambda sample was collected, allowing for the investigation of the decay channel Xi--->Lambdapi-. The deduced Xi-/(Lambda+Sigma0) production ratio of (5.6±1.2-1.7+1.8)×10-3 is significantly larger than available model predictions.
The invariant-mass spectrum of e+e- pairs produced in 12C+12C collisions at an incident energy of 2 GeV per nucleon has been measured for the first time. The measured pair production probabilities ...span over 5 orders of magnitude from the pi(0)-Dalitz to the rho/omega invariant-mass region. Dalitz decays of pi(0) and eta account for all the yield up to 0.15 GeV/c(2), but for only about 50% above this mass. A comparison with model calculations shows that the excess pair yield is likely due to baryon-resonance and vector-meson decays. Transport calculations based on vacuum spectral functions fail, however, to describe the entire mass region.
Dielectron spectroscopy at 1-2 AGeV with HADES Spataro, S.; Agodi, C.; Belver, D. ...
European physical journal. A, Hadrons and nuclei (Print),
11/2008, Letnik:
38, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
The HADES spectrometer at GSI (Darmstadt) is investigating the
e
+
e
-
pair production in p+p,
p
+
A
and
A
+
A
collisions. In this contribution we would like to highlight the physics motivations and ...the experiments performed so far, focusing mainly on the first results coming from
12
C +
12
C collisions at 1 and 2AGeV, and on preliminary results from
p
+
p
/
d
+
p
collisions at 1.25AGeV.
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