Results on $Lambda$p femtoscopy are reported at the lowest energy so far. At a beam energy of 1.76A~GeV, the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $Lambda
$ sample was collected, allowing for the investigation of $Lambda$ p correlations at small relative momenta. The experimental correlation function is compared to corresponding model calculations allowing the determination of the space-time extent of the $Lambda$p emission source. The $Lambda$p source radius is found slightly smaller than the pp correlation radius for a similar collis ion system. The present $Lambda$p radius is significantly smaller than that found for Au+Au/Pb+Pb collisio ns in the AGS, SPS and RHIC energy domains, but larger than that observed for electroproduction from He. Taking into account all available data, we find the $Lambda$p source radius to increase almost linearly with the number of participants to the power of one-third.
We report first results on a deep sub-threshold 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 (HADES) at SIS18/
GSI. A high-statistics and high-purity $Lambda$ sample was collected, allowing for the investigation of the decay channel $Xi^- to Lambda pi^-$. The deduced $Xi^-/(Lambda+Sigma^0)$ production ratio of $(5.6 pm 1.2 ^{+1.8}_{-1.7})cdot 10^{-3}$ is significantly larger than available model predictions.
Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragment
ation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.
