Correlations and fluctuations in hardonic multiciplicity distribution: The meaning of KNO scaling

Abstract

Charged hadronic multiplicity distributions at Fermilab, ISR and collider energies are shown to be described by generalized Bose-Einstein distributions of the type encountered in quantum optics. Systematic energy-dependent deviations from KNO scaling are well described by simple cases of this formula, which in the limit of large n have a simple and explicit scaling form, valid to a few percent at the CERN collider energy. It is suggested that this framework is generic, i.e., practically independent of dynamical details. The essential feature is that the field variables of the “radiant surface” for hadronic emission are distributed as gaussian random varibles (with k effective sources) as suggested by a typical central limit theorem argument. In order to bring the lower energy data into a form easily comparable with higher energy data, particularly for the crucial large multiplicity events ( n/ n ⪢ 1 , it is essential to remove the two charges of the “leading” particles from the counting rules. The long tail of the KNO distribution is to be identified with coherent fluctuations analogous to those occuring in the Hanbury-Brown-Twiss effect.