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The decay is dominantly an electromagnetic transition. Strangeness-conserving weak interactions should, however, admix a small component into the decay, leading to for the and even from an unpolarized . The most general amplitude for is ( is not second class (1) )

The average helicity of the or produced in the decay of an unpolarized is then (2)

If the is polarized, then the angular distribution of the outgoing with respect to the initial spin direction is

The parameter is a measure of the strength of the nonleptonic strangeness-conserving part of the weak-interaction Hamiltonian. and exchanges between free quarks in the and give

Quantum-chromodynamics effects do not appear to modify this result significantly, (3) although diagrams consisting of weak vertex corrections to gluon exchange could be important. If the weak amplitude is taken to be equal to that in (multiplied by ), then one finds

A measurement of these small weak-interaction effects should help to clarify the structure of the nonleptonic weak Hamiltonian.

Several authors (4) have suggested measurements of parity violation resulting from interference between the processes

This effect should be entirely swamped (except perhaps for a very small momenta) by the admixture into the photon-mediated decay discussed here.

This work was supported in part by the U. S. Department of Energy under Contract No. EY76-C-03-0068, and by a Feynman fellowship.

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