Evidence for virtual Δ++ knock-out from 9Be by 1 GeV protons

Inclusive differential cross sections of 4,6,8 He, 6,7,8 Li formation in p 9 Be interactions at T p = 1 GeV have been measured. Enhancement of the 8 He yield is observed in the spectator momentum range ( P c ), which is evidence for the process of virtual Δ ++ -isobar knock-out from 9 Be. The ratio of the spectroscopic factors of (Δ ++ 8 He) and (p 8 Li) configurations in 9 Be is estimated to be (6±3) × 10 −4 .