Physics
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Item Proton propagation in nuclei studied in the A dependence of the (e,e’p) reaction in the quasifree region(1989-08) Geesaman, D.F.; Gilman, R.; Green, M.C.; Holt, R.J.; Schiffer, J.P.; Zeidman, B.; Garino, G.; Saber, M.; Segel, R.E.; Beise, E.J.; Dodson, G.W.; Hoibraten, S.; Pham, L.D.; Redwine, R.P.; Sapp, W.W.; Williamson, C.F.; Wood, S.A.; Chant, N.S.; Roos, P.G.; Silk, J.D.; Deady, M.; Maruyama, X.K.The A dependence of the (e,e’p) reaction in the quasifree region has been measured at an average Q2 of 0.33 (GeV/c)2 for targets of 12C, 27Al, 58Ni, and 181Ta. The outgoing proton kinetic energy was 180±30 MeV. By comparing the ratio of (e,e’p) coincidence to (e,e’) singles yields, average proton transmissions are obtained for each target. The resulting ‘‘mean free path’’ or, more precisely, the attenuation length for protons in the nucleus is significantly longer than expectations based on the free nucleon-nucleon cross section.Item Measurement of 16O(γ,n)15O at medium energies(1989-05) Beise, E.J.; Dodson, G.; Garçon, M.; Høibråten, S.; Maher, C.; Pham, L.D.; Redwine, R.P.; Sapp, W.; Wilson, K.E.; Wood, S.A.; Deady, M.Exclusive differential cross sections for the 16O(γ,n)15O process have been measured for Eγ=150, 200, and 250 MeV and θL=49°, 59°, and 88°. This measurement is the first of its type to be reported for the energy region above the pion production threshold. An uncollimated bremsstrahlung beam was incident on an H2O target, and neutrons were measured with a recoil proton spectrometer with resolution sufficient to identify the residual 15O ground state. The results are compared to (γ,p) data and to calculations including effects from meson exchange currents.Item Reaction 58Ni(π+,2p) at 160 MeV(1986-07) Burger, W.J.; Beise, E.J.; Gilad, S.; Redwine, R.P.; Roos, P.G.; Chant, N.S.; Breuer, H.; Ciangaru, G.; Silk, J.D.; Blanpied, G.S.; Preedom, B.M.; Ritchie, B.G.; Blecher, M.; Gotow, K.; Lee, D.M.; Ziock, H.Data for the 58Ni(π+,2p) reaction at Tπ=160 MeV were obtained for a number of angle pairs. The resultant angular correlations for T1+T2>160 MeV (guaranteed pion absorption) peak at a separation angle corresponding to absorption on a deuteron at rest. However, simple estimates of initial- and final-state scatterings suggest that less than 50% of the absorption cross section arises from absorption on nucleon pairs. The data show little evidence for scattering of pions before absorption on nucleon pairs.