Superradiant 3/2^+ state and parity mixing in fast reaction-decay correlations

The 12C(3He,d)13 N reaction is studied in an experiment with a high-resolution magnetic spectrograph, in coincidence with protons detected in silicon detectors near the target. This allows for the observation of angular correlation patterns between the proton transfer and proton decays from populated unbound resonances. A formalism describing the spin polarization of direct reactions is developed to analyze these correlations, and verified on the known directionally asymmetric decay−distributions arising from parity mixing in the 13 N( 3/2-,5/2+ ) doublet. The same formalism is used to study the decays from the continuum-aligned, broad 3/2+ resonance at 7.9 MeV excitation energy, which arises from superradiant coupling. Again, the angular correlation patterns are asymmetric, which here is reproduced by adding an "artificial" 3/2− resonance with equal strength to the reaction formalism. This parity-mixing approach serves as a first approximation to a more advanced reaction model of rapid reaction and decay sequences.