Probing Nuclear forces beyond the drip-line using the mirror nuclei $^{16}$N and $^{16}$F

Radioactive beams of O-14 and O-15 were used to populate the resonant states 1/2(+), 5/2(+) and 0(-), 1(-), 2(-) in the unbound F-15 and F-16 nuclei, respectively, by means of proton elastic scattering reactions in inverse kinematics. Based on their large proton spectroscopic factor values, the resonant states in F-16 can be viewed as a core of O-14 plus a proton in the 2s(1/2) or 1d(5/2) shell and a neutron in 1p(1/2). Experimental energies were used to derive the strength of the 2s(1/2)-1p(1/2) and 1d(5/2)-1p(1/2) proton-neutron interactions. It is found that the former changes by 40% compared with the mirror nucleus N-16, and the latter changes by 10%. This apparent symmetry breaking of the nuclear force between mirror nuclei finds explanation in the role of the large coupling to the continuum for the states built on an l = 0 proton configuration.