New precision mass measurements of neutron-rich calcium and potassium   isotopes and three-nucleon forces
  We present precision Penning-trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system the mass of $^{51}$K was measured for the first time, and the precision of the $^{51,52}$Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, $^{52}$Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces at neutron-rich extremes. 
A.T. Gallant, J.C. Bale, T. Brunner, U. Chowdhury, S. Ettenauer, A.   Lennarz, D. Robertson, V.V. Simon, A. Chaudhuri, J.D. ...
nucl-ex nucl-th