Single and multinucleon antiproton-4He annihilation at rest

The antiproton annihilation at rest in a NTP 4He-gas target has been studied by means of the Obelix spectrometer installed at the LEAR accelerator of CERN. Reactions with production of 2π−2π+, 2π−3π+, 2π−2π+p, 2π−π+2p, 2π−3p (with pion momentum > 80 MeV/c and proton momentum > 300 MeV/c) have been selected and single- and multinucleon annihilations identified. For the first time some known mesonic and baryonic resonances have been observed in antiproton-4He annihilations and branching ratios are evaluated for a number of reaction channels.