RPA puzzle in 12C weak decay processes

We explain the origin of the difficulties that appear in a straightforward application of the QRPA in 12C, and we demonstrate that it is imperative to use the projected QRPA (PQRPA). Satisfactory results, not only for the weak processes among the ground states of the triad {12B,12C,12N}, but also for the inclusive ones are obtained. We sketch as well a new formalism for the neutrino–nucleus interaction that furnishes very simple final formulae for the muon capture rate and neutrino induced cross sections.