Recent results on antiproton annihilation in 4He

With experimental data of \({\bar p}\) annihilation at rest on nuclei of 4He, collected by the Obelix spectrometer (LEAR, CERN), we have studied a number of reactions with 4 and 5 charged particles in the final state, distinguishing the annihilations on more than one nucleon, and with strangeness production. The main results of our observations are: (a) a higher (up to 20 times) strangeness production in 4He than in H; (b) the evidence of a possible signature of a \(\overline{K}pp\) (\(\overline{K} ppn\)) bound state; (c) a measurement of a double strangeness production (2K+) and a hint for some production yields of double-strange bound systems like 2K−2n; (d) a signal compatible with the baryonic \(\Theta^+(1530)\) resonance, interpreted as a pentaquark system.