Gamow-Teller strengths in the A=14 multiplet: A challenge to the shell model

A new experimental approach to the famous problem of the anomalously slow Gamow-Teller (GT) transitions in the β decay of the A=14 multiplet is presented. The GT strength distributions to excited states in C14 and O14 were studied in high-resolution (d,He2) and (He3,t) charge-exchange reactions on N14. No-core shell-model calculations capable of reproducing the suppression of the β decays predict a selective excitation of Jπ=2+ states. The experimental confirmation represents a validation of the assumptions about the underlying structure of the N14 ground state wave function. However, the fragmentation of the GT strength over three 2+ final states remains a fundamental issue not explained by the present no-core shell model using a 6 ω model space, suggesting possibly the need to include cluster structure in these light nuclei in a consistent way.