The cross sections of the processes 4He(γ,p)3H and 4He(γ,n)3He are calculated taking into account the full final state interaction via the Lorentz integral transform method. This is the first consistent microscopic calculation beyond the three-body breakup threshold. The results are obtained with a semirealistic central nucleon-nucleon potential including also the Coulomb force. The cross sections show a pronounced dipole peak at 27 MeV which lies within the rather broad experimental band. At higher energies, where experimental uncertainties are considerably smaller, one finds a good agreement between theory and experiment. The calculated sum of three- and four-body photodisintegration cross sections is also listed and is in fair agreement with the data.
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We would like to thank M. A. Marchisio for supplying us with the computer code for the Lanczos algorithm. S.Q. acknowledges for support. The work of N.B. was supported by the Israel Science Foundation (Grant No. 202∕02). V.D.E. thanks the Department of Physics of the University of Trento for support and hospitality.