Two-nucleon knockout contributions to the 12^{12}C(e,e′p)(e,e'p) reaction in the dip and {Δ\Delta}(1232) regions

The contributions from $^{12}$C$(e,e'pn)$ and $^{12}$C$(e,e'pp)$ to the semi-exclusive $^{12}$C$(e,e'p)$ cross section have been calculated in an unfactorized model for two-nucleon emission. We assume direct two-nucleon knockout after virtual photon coupling with the two-body pion-exchange currents in the target nucleus. Results are presented at several kinematical conditions in the dip and $\Delta$(1232) regions. The calculated two-nucleon knockout strength is observed to account for a large fraction of the measured $(e,e'p)$ strength above the two-nucleon emission threshold.Comment: 12 Revtex pages, 4 postscript figures (available upon request), University of Gent preprint SSF94-02-0

Viscosity and fission time scale of^{156}Dy

In the fusion-fission reaction Ar-40+Cd-116-->Dy-156-->fission, performed at beam energies E(b) = 216 MeV and 238 MeV, gamma rays were measured in coincidence with fission fragments. The gamma-ray spectra are interpreted using a modified version of the statistical-model code CASCADE. From a comparison of the experimental and calculated spectra it is deduced that the nuclear viscosity is in the range 0.01 <gamma <4. The extracted fission time scale is of the order of 10(-19) s

The 4^4He(e,e′p)(e,e'p) Cross Section at Large Missing Energy

The $(e,e'p)$ reaction on $^{4}{He}$ nuclei was studied in kinematics designed to emphasize effects of nuclear short-range correlations. The measured cross sections display a peak in the kinematical regions where two-nucleon processes are expected to dominate. Theoretical models incorporating short-range correlation effects agree reasonably with the data.Comment: 4 pages LaTeX, using espcrc1.sty and wrapfig.sty (included), two figures. Talk presented by J. Templon at the 15th Int. Conf. on Few-Body Problems in Physics, Groningen, The Netherlands, 22-26 July, 199

Lack of evidence for a superdeformed band in^{192}Pb

An experiment was performed to measure the lifetimes of the states in the superdeformed band reported in Pb192. No evidence for such a band was found, despite the fact that the experimental conditions were nearly identical to those of an earlier measurement where this band was proposed. The problems and questions encountered in the analysis are described. The arguments presented here indicate that further measurements are needed to establish the existence of a superdeformed band in this nucleus unambiguously

Electron-induced neutron knockout from 4^{4}He

The differential cross section for electron-induced neutron knockout in the reaction 4He(e,e′n)3He has been measured for the first time with a statistical accuracy of 11%. The experiment was performed in quasielastic kinematics at a momentum transfer of 300  MeV/c and in the missing-momentum range of 25–70  MeV/c. The comparison of the data with theoretical calculations shows an impressive increase of the cross section resulting from final state interaction effects. Specifically , the p−n charge-exchange process dominates the cross section in this kinematical regime. (APS