Delayed fission from the antiproton annihilation in 209Bi — evidence for hypernuclear decay

Abstract Delayed fission following the annihilation of stopped antiprotons in 209 Bi has been observed with a yield of approximately 3 × 10 −4 . The lifetime for delayed fission as measured by the recoil-distance technique is (2.5 +2.5 −1.0 )×10 −10 s. The observed delayed fission is interpreted as resulting from the decay of hypernuclei in the region of masses near 200 produced in the annihilation of antiprotons in 209 Bi.