Multiplicity distribution of colour dipoles at small~$x$

Abstract

The colour dipole multiplicity distribution is analysed for the wave function of a heavy onium state at small $x$. Numerical results for the average multiplicity and the effect of cutoffs on its power growth are presented. Then, the full multiplicity distribution is analysed: the second multiplicity moment is derived and the tail of the distribution is shown to behave as $\exp (-{\log }^{2}n)$. These results are confirmed by a Monte Carlo simulation which also gives the fluctuations in the spatial density of dipoles.

Comments: submitted as uuencoded postscript file of whole paper: 14 pages with 5 figures. Postscript also available from http://www.hep.phy.cam.ac.uk/theory/papers/index.html