A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of
on the 3
level is ...derived. Comparing this value with the number of successfully reconstructed
hyperons allows to determine an upper limit on the ratio
, which is confronted with statistical and coalescence-type model calculations.
.
Results on the deep sub-threshold production of the short-lived hadronic resonance K*(892)
0
are reported for collisions of Ar + KCl at 1.76A GeV beam energy, studied with the High Acceptance ...Di-Electron Spectrometer (HADES) at SIS18/GSI. The K*(892)
0
production probability per central collision of
and the K*(892)
0
/K
0
ratio of
are determined at the lowest energy so far (
i.e.
deep below the threshold for the corresponding production in nucleon-nucleon collisions,
MeV). The K*
0
/K
0
ratio is compared with results of other experiments and with the predictions of the UrQMD transport approach and of the statistical hadronization model. The experimental K*
0
yield and the K*
0
/K
0
ratio are overestimated by the transport model by factors of about five and two, respectively. In a chemically equilibrated medium the ratio corresponds to a temperature of the thermalized system being systematically lower than the value determined by the yields of the stable and long-lived hadrons produced in Ar + KCl collisions. From the present measurement, we conclude that sub-threshold K* production either cannot be considered to proceed in a system being in thermal equilibrium or these short-lived resonances appear undersaturated, for example as a result of the rescattering of the decay particles in the ambient hadronic medium.
We present an analysis of the hyperons Λ(1405) and Σ(1385)
+
for p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the
H
igh
A
cceptance
D
i-
E
lectron
S
pectrometer (HADES). A ...Λ(1405) signal could be reconstructed in both charged decay channels Λ(1405)→Σ
±
π
∓
. The obtained statistics of the Σ(1385)
+
signal allows also differential studies.
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 + Sigma;{0}) production ratio of (5.6 +/- 1.2_{-1.7};{+1.8}) x 10;{-3} is significantly larger than available model predictions.
We report on baryon resonance production and decay in proton-proton collisions at a kinetic energy of \(3.5\) GeV based on data measured with HADES. The exclusive channels \(pp \rightarrow ...np\pi^{+}\) and \(pp \rightarrow pp\pi^{0}\) as well as \(pp \rightarrow ppe^{+}e^{-}\) are studied simultaneously for the first time. The invariant masses and angular distributions of the pion-nucleon systems were studied and compared to simulations based on a resonance model ansatz assuming saturation of the pion production by an incoherent sum of baryonic resonances (R) with masses \(<2~\) GeV/\(c^2\). A very good description of the one-pion production is achieved allowing for an estimate of individual baryon-resonance production-cross-sections which are used as input to calculate the dielectron yields from \(R\rightarrow pe^+e^-\) decays. Two models of the resonance decays into dielectrons are examined assuming a point-like \(RN \gamma^*\) coupling and the dominance of the \(\rho\) meson. The results of model calculations are compared to data from the exclusive \(ppe^{+}e^{-}\) channel by means of the dielectron and \(pe^+e^-\) invariant mass distributions.
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.
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