Charge dependent potentials and neutron-neutron scattering length

Abstract

Nuclear charge-dependent potentials of Brueckner and Watson type are obtained by inserting different masses of the charged and neutral pions. The pair formation terms are completely suppressed following the work of Klein. These potentials are then employed to calculate the charge dependence of the 1S scattering lengths a np and a pp, and the energy difference of the first T = 1 state of 6Li and 6He. The three coupling constants for π-N systems and the hard core radius are treated as open parameters to be fixed by empirical data. It is found that the coupling constants are very close to one another except for a small deviation from charge symmetry. By use of the coupling constants thus obtained the scattering length for the neutron-neutron system in an 1S state is calculated. The results are compared with a recent measurement and satisfactory agreement is obtained.