Be9 photodisintegration cross section within cluster effective field theory

A low-energy calculation of 9 Be photodisintegration cross section is presented within an 𝛼⁢𝛼⁢𝑛 cluster approach. The 𝛼⁢𝑛 and 𝛼⁢𝛼 contact interactions are derived from cluster effective field theory. The two-body potentials defined in momentum space are regularized by a Gaussian cutoff. The associated low-energy constants are found by comparing the calculated low-energy 𝑇 matrix with its effective range expansion. A three-body state-dependent potential is also introduced in the model. First, the 9 Be three-body binding energy is studied within the nonsymmetrized hyperspherical harmonics method. Then, the low-energy cross section is calculated via the Lorentz integral transform method, focusing on the dominant electric dipole transitions. A twofold evaluation of the nuclear current matrix element is presented, employing both the electric dipole transition operator (Siegert theorem) and the one-body convection current operator. This approach is adopted to allow for a discussion of the effect of the many-body currents.