annihilation at rest into five pions

annihilation at rest into five pions was studied in the ASTERIX spectrometer by stopping antiprotrons from LEAR in a H2 or D2 gas target. In annihilations in H2 leading to the π+π−π+π−π0 final state, the invariant mass spectra of two, three, and four pions show no evidence for any new narrow states. In the difference of the four pion mass spectra recoiling against a π− and those recoiling against a π+ shows a resonance-like structure (“ζ (1480)”), confirming a previous analysis with a smaller event sample. The ζ (1480) mass is shown to depend strongly on the momentum of the spectator proton. In H2, we searched for the ζ (1480) in the reaction (1480), ζ (1480) →π+π−π+π− to clarify whether the ζ (1480) is identical to the 4π-mode of thef2 (1520). No evidence for this decay mode was found. A prominent resonance in innihilation into five pions is the ω meson. We find two quasi-two-body intermediate states: and (1235). The mass and width of theb1 (1235) are determined to be:(1) $$M_{bI} = 1225 \pm 5\user2{MeV, }\Gamma _{b1} = 113 \pm 12MeV.$$