A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of 6 Li projectiles on a carbon target at 2 A GeV was performed. Signals of the Λ-hyperon and 3 Λ H and 4 Λ H hypernuclei were observed for final states of p+π − , 3 He+π − and 4 He+π − , respectively, with significance values of 6.7, 4.7 and 4.9σ. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be 262 +56 −43 ± 45 ps for Λ, 183 +42 −32 ± 37 ps for 3 Λ H, and 140 +48 −33 ± 35 ps for 4 Λ H.

Hypernuclear production cross sections have been deduced for the first time with induced reaction of heavy ion beam on fixed target and by means of the invariant mass method by the HypHI Collaboration exploiting the reaction of 6 Li + 12 C at 2 A GeV or √ s N N = 2.70 GeV. A production cross section of 3.9 ± 1.4 μb for 3 H and of 3.1 ± 1.0 μb for 4 H respectively in the projectile rapidity region was inferred as well as the total production cross section of the hyperon was measured and found to be equal to 1.7 ± 0.8 mb. A global fit based on a Bayesian approach was performed in order to include and propagate statistical and systematic uncertainties. Production ratios of 3 H/ 4 H, 3 H/ and 4 H/ were included in the inference procedure. The strangeness population factors S 3 and S 4 of 3 H and 4 H respectively were extracted. In addition, the multiplicities of the hyperon, 3 H, and 4 H together with the rapidity and transversal momentum density distributions of the observed hypernuclei were extracted and reported.

International audienceThe N/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at the GSI Schwerionen Synchrotron (SIS). Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. For the interpretation of the data, calculations with the statistical multifragmentation model for a properly chosen ensemble of excited sources were performed. The parameters of the ensemble, representing the variety of excited spectator nuclei expected in a participant-spectator scenario, are determined empirically by searching for an optimum reproduction of the measured fragment-charge distributions and correlations. An overall very good agreement is obtained. The possible modification of the liquid-drop parameters of the fragment description in the hot freeze-out environment is studied, and a significant reduction of the symmetry-term coefficient is found necessary to reproduce the mean neutron-to-proton ratios 〈N〉/Z and the isoscaling parameters of Z⩽10 fragments. The calculations are, furthermore, used to address open questions regarding the modification of the surface-term coefficient at freeze-out, the N/Z dependence of the nuclear caloric curve, and the isotopic evolution of the spectator system between its formation during the initial cascade stage of the reaction and its subsequent breakup

The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of (124)Sn and radioactive beams of (124)La and (107)Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (DeltaT approximately 0.6 MeV) appear for residue production near the onset of multifragmentation.