The extraction of the bare triple-Pomeron vertex; a crucial ingredient for diffraction

Abstract

The triple-Pomeron coupling lies at the heart of the predictions for high energy diffractive processes. We explain why the existing determinations, which use single-particle inclusive hadronic data a+b -> a+Y, underestimate the value of the bare coupling, due to the neglect of soft rescattering which populates the rapidity gaps. We describe how data for the process gamma+p -> J/psi +Y can be used to give a much more reliable estimate of the bare coupling. We use the existing, fragmentary, J/psi data from HERA to show that the triple-Pomeron coupling is probably about 3 times larger than the previous determinations. We emphasize the importance of an explicit measurement of the mass spectrum of the Y system which accompanies J/psi production at HERA. The consequences for ultra high energy cosmic ray showers are mentioned.