Testing Qcd Predictions for Multiplicity Distributions at Hera

On the basis of a recently introduced generalization of the negative binomial distribution the influence of higher-order perturbative QCD effects on multiplicity fluctuations are studied for deep inelastic e + p scattering at HERA energies. It is found that the multiplicity distributions measured by the H1 Collaboration indicate violation of infinite divisibility in agreement with pQCD calculations. Attention is called to future experimental analysis of combinants whose nontrivial sign-changing oscillations are predicted using the generalized negative binomial law. E-mail: [email protected] Over the past 15 years of experimental and theoretical study of multiplicity distributions (MDs) in a variety of collision processes a universal law emerged known as the negative binomial (NB) regularity [1]. The negative binomial distribution (NBD) proved to be very successful in describing the observed shape of MDs not only in full phase-space but also in restricted subdomains. At the same time the NBD naturally arises in branching processes which share many common features with the parton cascades of QCD. Thus the theoretical basis of the NB regularity is well founded, at least qualitatively. The NBD has two parameters, the shape parameter k and the mean value 〈n〉. Its analytic form can be written as Pn = 1 n! Γ(k + n) Γ(k) (