Resonance Mixing , “ Dipoles ” , and ‘ Zombies ”

If the lively discussion of the p-w system and the A2 splitting at this conference is any guide, the problems of resonance mixtures will continue to be an active one for some time, Therefore I would like to review here a simple formalism for treating the problem and in particular to emphasize certain points: 1. The parameter which gives the nonorthogonality of the underlying states caused by their mixing is in principle directly measurable in a “missing-mass” type experiment, being given by the interference term between the Breit-Wigner shapes. Thus the need for a large interference term in the A2 rules out any kind of “weak mixing” explanation. 2. Perhaps even more striking than the “dipole” is the apparent need in the A2 problem for a “dead” state, which couples neither to production nor decay. This seems forced by the similiarity of the A2 effect in all decay modes. Perhaps such states should be looked for in isolation. Simple formulae are given for the cross section shapes for such phenomena. -