Large multiplicity fluctuations and saturation effects in onium collisions

Abstract

This paper studies two related questions in high energy onium-onium scattering: the probability of producing an unusually large number of particles in a collision, where it is found that the cross section for producing a central multiplicity proportional to $k$ should decrease exponentially in $\sqrt{k}$. Secondly, the nature of gluon (dipole) evolution when dipole densities become so high that saturation effects due to dipole-dipole interactions become important: measures of saturation are developed to help understand when saturation becomes important, and further information is obtained by exploiting changes of frame, which interchange unitarity and saturation corrections.Comment: 30 pages LaTeX2e, 11 figures included using epsfig. Compressed postscript of whole paper also available at http://www.hep.phy.cam.ac.uk/theory/papers