EMERGENCE OF JET DOMINANCE IN GAMMA-P INTERACTIONS AT FIXED-TARGET ENERGIES

In Fermilab experiment E683 we have used a large solid angle calorimet er to study the production of hadronic events with large transverse en ergy in gamma p and pi p collisions at center-of-mass energies from 20 to 25 GeV. We observe a sudden shift in yp event topology with increa sing transverse energy, indicative of the emergence of jet dominance. This is the first observation of such a shift in event topology in fix ed-target interactions. pi p interactions in the same kinematic region and under identical triggering conditions exhibit only a slight shift in event topology.