The 4 He(γ,n)3 He Reaction with Full Final-State Interaction

Abstract

The total cross sections of the processes 4 He(γ, p) 3 H and 4 He(γ, n) 3 He are calculated. For these exclusive reactions we investigate the question of the giant dipole peak height, but we also consider higher energies. The calculation includes full Final State Interaction (FSI) via the Lorentz Integral Transform (LIT) approach [1] and employs the semi-realistic MTI-III potential [2]. The LIT method has already been successfully applied to the calculation of the exclusive d(e, e ′ p)n reaction [3]. We would like to emphasize that FSI is taken rigorously into account also in the region beyond the three-body break-up threshold. From the total photoabsorption cross section for the same potential calculated in [4,5] we are also able to determine the sum of three-and four-body break-up cross sections. Here (as well as in [5,4]) only the transitions induced by the unretarded dipole operator D are taken into account. The total exclusive cross section of the photodisintegration of 4 He into the two-fragments (N , 3 ), where N represents the scattered proton (neutron) and 3 the 3 H ( 3 He) nucleus, is given byWith µ and k we indicate the reduced mass and the relative momentum of the two fragments, respectively; ω γ is the incident photon energy, E α and Ψ α are energy and wave function of the α particle bound state, whereasis the formal scattering solution of the (N,3) channel at energy E f : φ 1 is the unperturbed wave function describing the relative motion of nucleon 1 with respect to nucleons 2, 3 and 4 bound to form nucleus 3, V 1 is the corresponding N-3 interaction part of the full nuclear Hamiltonian H and A is the antisymmetrization operator. The Coulomb interaction is taken into account both by using Coulomb wave functions for φ 1 in the (p, 3 H) channel (instead of spherical Bessel functions for (n, 3 He)), and in the calculation of the bound