Production of nuclei and hypernuclei in pion-induced reactions near threshold energies

The ultrarelativistic quantum molecular dynamics model is employed to simulate π^-+C and π^-+W collisions at plab=1.7 GeV motivated by the recent HADES results. By comparing the proton and Λ transverse momentum spectra, it was observed that the data and transport model calculation show a good agreement, if cluster formation is included to obtain the free proton spectra. Predictions of light cluster (d, t, ³He, ⁴He, as well as _Λ³H and ΞN) multiplicities and spectra are made using a coalescence mechanism. The resulting multiplicities suggest that the pion beam experiment can produce a substantial amount of _Λ³H, especially in π^-+W collisions due to the stopping of the Λ inside the large tungsten nucleus. The findings are supplemented by a statistical multifragmentation analysis suggesting that even larger hyperfragments are produced copiously. It is suggested that even double strange hypernuclei are in reach and might be studied in more detail using a slightly higher pion beam momentum.