Phenomenology of nuclear forces

  • Strongly repulsive core. The \( s \)-wave phase shift becomes negative at \( \approx 250 \) MeV implying that the singlet \( S \) has a hard core with range \( 0.4-0.5 \) fm.
  • Charge independence (almost). Two nucleons in a given two-body state always (almost) experience the same force. Modern interactions break charge and isospin symmetry lightly. That means that the pp, neutron-neutron and pn parts of the interaction will be different for the same quantum numbers.
  • Non-central. There is a tensor force. First indications from the quadrupole moment of the deuteron pointing to an admixture in the ground state of both \( l=2 \) (\( ^3D_1 \)) and \( l=0 \) (\( ^3S_1 \)) orbital momenta.