Spin correlation measurements in pseudoscalar meson photoproduction

Because polarized photon beams and polarized proton targets have improved considerably and the techniques for measuring recoil bary on polarizations are continually improving, it is becoming feasible to measure double and triple spin correlations in pseudoscalar meson photoproduction. Of the large number of such experiments possible, only a few will add significantly ne new information to that already obtained from the existing cross section and limited polarization measurements. Using a simple, general, and transparent method, we shall show that all such measurements fall into three classes: (a) those which are equivalent to more simple measurements, (b) those which are highly bounded by previous measurements, and (c) those which yield truly new information.