PRIMAKOFF SCATTERING FOR POLARIZED PHOTONS OR POLARIZED PROTONS

We present a way to measure the axial coupling of the proton for the n eutral strangeness current in coherent pi0 production induced by photo n-proton scattering. By means of the gamma-Z-pi0 triangle anomaly, the parity violating asymmetries for polarized photon or polarized proton Primakoff effect filter the couplings so as to leave the proton axial coupling only. We calculate the relevant observables induced by the e lectroweak interference and give results for regions of energy and Q2 of possible experimental interest. The polarized proton asymmetry is p redicted to be 10(-6)-10(-5) when Q2 approximately 0.1-0.5 GeV2.