2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/38003A search for photoproduction events which contain a rapidity gap between the two highest transverse energy jets has been conducted at HERA using the ZEUS detector. The jets have transverse energies greater than 6~GeV, and are separated by pseudorapidity intervals of up to four units. The fraction of events containing a gap is measured as a function of the gap-width. It is expected that this gap-fraction will fall exponentially with the gap-width, until the dominant gap-production mechanism becomes colour singlet exchange, at which point it will plateau. An indication of a plateau in the measured gap-fraction has been found, at a higher level than that expected from electroweak exchange.7 pages, 4 postscript figures, lines now wrapped to 80 charactersHigh Energy Physics - Experimenttext