A four-nucleon calculation of the total ${}^4\mathrm{He}$ photodisintegration cross section is performed. The full final-state interaction is taken into account for the first time. This is achieved via the method of the Lorentz integral transform. Semirealistic $\mathrm{NN}$ interactions are employed. Different from the known partial two-body ${}^4\mathrm{He}(\gamma ,n{)}^3\mathrm{He}$ and ${}^4\mathrm{He}(\gamma ,p{)}^3\mathrm{H}$ cross sections our total cross section exhibits a pronounced giant resonance. Thus, in contrast to older $(\gamma ,np)$ data, we predict quite a strong contribution of the $(\gamma ,np)$ channel at the giant resonance peak energy.

• Received 21 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.4015