**
**PION PHOTOPRODUCTION and the ISOSPIN = 0,1 RULE

Low energy photopion production is of fundamental interest because of:
(a) its relatively simple dynamics;
(b) low energy theorems based on chiral symmetry
and gauge invariance;

(c) tests of the
isospin properties of the electromagnetic interactions, and their T-invariance;

(d) quark model predictions for the magnitudes of the electric and magnetic
Delta(1232) -> N gamma transitions.

I will just summarize my contribution to (a) and (c).

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Dynamics of low energy pion photoproduction

A.Donnachie and G.Shaw, Ann. Phys. (NY) 37(1966)333 [97
citations]

This was the main paper in my Ph.D. thesis. It used fixed-t dispersion
relations and recently determined pion nucleon phase shifts to show
that for photon enegies below 500 MeV, the multipole amplitudes could be
understood in terms of the following
dominant processes: (a) the Born terms(ie the nucleon and pion
exchange contributions); (b,c) contributions from the Delta(1232) baryon
resonance; and (d) unitarity/rescattering corrections in non-resonant multipoles.

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Isospin properties of the electromagnetic current

In preparation.