Results obtained by solving Alt-Grassberger-Sandhas ͑AGS͒-type integral equations for the photodisintegration of 4 He, employing the Malfliet-Tjon potential, are compared with the latest experimental data. Good agreement between theory and experiment is found in electric dipole approximation for the total cross section, but the differential cross sections differ at higher energies. This discrepancy is reduced, but not fully removed by taking into account the electric quadrupole contributions. In order to get some feeling for the sensitivity to the underlying potential, we also show calculations based on the Yamaguchi potential. They differ from the Malfliet-Tjon results in a way which resembles the trends known from triton photodisintegration. ͓S0556-
Three- and four-nucleon photodisintegration processes are quite efficiently
treated by means of effective two-body integral equations in momentum space. We
recall some aspects of their derivation, present previous and most recent
results obtained within this framework, and discuss general features, trends
and effects observed in these investigations: At low energies final-state
interaction plays an important role. Even more pronounced is the effect of
meson exchange currents. A considerable potential dependence shows up in the
low-energy peak region. The different peak heights are found to be closely
correlated with the corresponding binding energies. Above the peak region only
the difference between potentials with or without p-wave contributions remains
relevant. In the differential cross sections the electric quadrupole
contributions have to be taken into account. The remarkable agreement between
theory and experiment in $p$-$d$ radiative capture is achieved only when
incorporating this contribution, together with most of the above-mentioned
effects. In the final part of this report we briefly review also methods
developed, and results achieved in three- and four- nucleon
electrodisintegration. We, in particular, compare them with a recent access to
this problem, based on the construction of nucleon-nucleus potentials via
Marchenko inversion theory.Comment: 20 pages LaTeX and 22 postscript figures included, uses epsfig.sty
and espcrc1.sty. Invited talk at the XVth International Conference on
Few-Body Problems in Physics (22-26 July, 1997, Groningen, The Netherlands).
To be published in the conference proceedings in Nucl. Phys.
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