Second-Class Currents and Experimental Nuclear Mirror Asymmetry

Weak-current effects can explain the experimentally observed mirror asymmetry in nuclear $\beta$ decays despite the absence of energy dependence predicted by a naive model for second-class currents. Meson exchange with $\omega \to \pi$ decay in the nucleus can result either from second-class currents or electromagnetic $\omega \rho$ mixing and can be enhanced by a factor $A$ due to nuclear coherence.