A search fot photon-induced asymmetry in the azimuthal distribution of giant air showers

McBreen and Lambert (1981) pointed out that photons of energy above 1019 eV would produce pairs in the magnetic field of the earth. Such an effect might be used to search for a ux of primary photons at extreme energies. This issue has recently become topical because of the predictions of large photon uxes above 1019 eV from the decay of super-heavy relic particles and because the Pierre Auger Observatory offers promise of large number of events even at 1020 eV. Bertou et al (2000) have explored the potential of the Auger instrument for such a search in some detail. One of us (Hinton 1999, unpublished) has searched for an azimuthal aymmetry using a sample of Haverah Park events without success. We will report the results of an extended search for which we have included a new sample of events above 1019 eV that arrived at large zenith angles (Ave et al. 2000).