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Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 22: Plenar

HK 22.3: Gruppenbericht

Dienstag, 17. März 1998, 10:30–11:00, P

Short-range-correlations in 16O studied with the reaction 16O(e,epp)14C — •C.J.G. Onderwater1,2, R. Starink1,2, K. Allaart1,2, W.J.W. Geurts1,2, W.H.A. Hesselink1,2, P. Heimberg1,2, A.R. Pellegrino1,2, M. Steenbakkers1,2, J.A. Templon1,2, D.L. Groep2, E.C. Aschenauer2, E. Jans2, L. Lapikás2, W-J. Kasdorp2, G. van der Steenhoven2, M. van Batenburg2, J.J. van Leeuwe2, J.J.M. Steijger2, M.A. van Uden2, E. Cisbani3, S. Frullani3, F. Garibaldi3, M. Iodice3, G-M. Urciuoli3, Th.S. Bauer4,2, D.J. Boersma4,2, A. Misiejuk4,2, N. Kalantar-Nayestanaki5, R. De Leo6, R. Perrino7, and L.B. Weinstein81Free University, Amsterdam,The Netherlands — 2NIKHEF, Amsterdam, The Netherlands — 3INFN-Sezione Sanità, Rome, Italy — 4Universiteit Utrecht, Utrecht, The Netherlands — 5KVI, Groningen, The Netherlands — 6Universitá di Bari, Italy — 7INFN-Lecce, Italy — 8Old Dominion University, Norfolk, USA

The reaction 16O(e,epp)14C has been studied at an energy transfer in the range ω=160−260 MeV and an average three-momentum transfer q=300 MeV/c. The electrons were scattered off 16O nuclei contained in a waterfall target. Triple coincidence data were taken over a wide range of proton emission angles using two highly segmented plastic scintillator arrays with solid angles of 235 and 550 msr, respectively. >From the momenta of the scattered electrons and the emitted protons the excitation-energy and the momentum of the residual 14C nucleus were determined. If final state interactions are neglected the latter is equal to the centre-of-mass momentum of the proton-pair in 16O. A first indication for the importance of short-range-correlations (SRC) has been obtained by comparing the data, taken for ω=190−230 MeV with a simple factorized-approach of the cross sections for the transitions to the ground-state and the lowest excited states in 14C. It is found that the excitation-energy spectrum of the 14C nucleus and the corresponding pair centre-of-mass momentum distributions can be reconciled with direct knock-out of two protons from the 1p shell and that the proton-pairs were most likely in a 1S0 state. This result is confirmed by calculations, that fully account for the dynamics of the protons in the initial and final state and the various processes contributing to the reaction. These calculations indicate that knockout of 1S proton-pairs mainly originates from SRC, whereas emission of 3P pairs is largely due to two-body (Δ) currents. Additional information on the reaction mechanism, in particular on the contribution of two-body hadronic currents, has been obtained from the measurements at various values of the energy transferred by the virtual photon.

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