DETERMINING THE GLUON DISTRIBUTIONS IN THE PROTON AND PHOTON FROM 2-JET PRODUCTION AT HERA

Two-jet production from the direct photon contribution at HERA is a se nsitive measure of the small-x gluon in the proton. We propose measure ments of ratios of the jet cross-sections which will clearly distingui sh between gluons with or without singular behaviour at small x. Furth ermore, we show that analogous ratio measurements for the resolved pho ton contribution provide a sensitive way of determining the gluon dist ribution in the photon.