Differential distributions for the double photoionization of helium

We have calculated in the dipole approximation the triple and double differential distributions for the double photoionization of helium far away from the threshold. We have demonstrated that there is a kinematical region where this distribution is enhanced. It corresponds to a real intermediate state in the process. We obtained a simple analytical expression for the asymmetry coefficient, which is valid if the energies of the photoelectron exceeds strongly the single-particle binding energy. The results are in good agreement with the numerical results obtained in the literature