Narrow Results

Nuclear physics programs recently carried out at the RCNP cyclotron facility have been discussed with emphasis on the two subjects in relation to the chiral symmetry. One is the three-nucleon reactions at intermediate energies and effects of the three-nucleon force, which may be consistently understood in the chiral effective field theory. Another is the high-resolution measurements of spin-isospin excitations and a possibility for explaining the fine-structures in giant resonances by the chiral mean field model.

We discuss the importance of the three-nucleon isospin $T=3/2$ component in elastic neutron-deuteron scattering and in the deuteron breakup reaction. The contribution of this amplitude originates from charge-independence breaking of the nucleon-nucleon potential. We study the magnitude of that contribution to the elastic scattering and breakup observables, taking the Av18 nucleon-nucleon potential alone or combined with the Urbana IX three-nucleon force as well as the locally regularized chiral N⁴LO nucleon-nucleon potential alone or supplemented by the chiral N²LO three-nucleon force. We find that the isospin $T=3/2$ component is important for the breakup reaction and the proper treatment of charge-independence breaking in this case requires the inclusion of the ${}^1{S}_0$ state with isospin $T=3/2$. For neutron-deuteron elastic scattering the $T=3/2$ contributions are insignificant and charge-independence breaking can be accounted for by neglecting $T=3/2$ component and using the effective t-matrix generated with the so-called $“2/3-1/3^{″}$ rule.