An impact-parameter model for multiplicity distributions

We study a model for hadron-hadron scattering in which at each value of impact parameter the multiplicity follows a Poisson distribution whose mean is determined by the profile function. This model permits a calculation of the full multiplicity distribution once the profile function is given. Geometrical scaling and KNO scaling are linked together; the rise in σ_el/σ_tot at the \(Sp\bar pS\) implies a violation of KNO scaling. The energy dependence of moments of the multiplicity distribution is “predicted” quite well. Implications for hard-scattering models are discussed.