The inclusive cross section times branching ratio for J/ψ→e+e- has been measured in the forward region in the UA6 experiment for pp and pp collisions at √s = 24.3 GeV. The ratio of the pp to pp cross sections is found to be 0.76 ± 0.14 ± 0.06. This demonstrates that gluon-gluon fusion dominates over quark-antiquark annihilation in the formation of the cc state.
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We are indebtedto J.P. Guillet for his help with the theoreticailn terpretatioonf our data. We wish to thank the CERN PS and SPS Divisionsf or the efficient operationo f the antiprotonso urcea ndthe SPS Collider.W e also thankt heEP and SPS Divisionsf or their extensives upportd uringboth the installation and the runnings tageso f UA6. Finally, we gratefully acknowledgteh ed edicatedsu pporto f the UA6 technical and secretariaslt aff.This work is partiallys up- portedb y the Swiss NationalS cienceF oundationt,h e US National Science Foundationa nd US Department of Energy.