The negative binomial distribution in quark jets with fixed flavour
  We show that both the multiplicity distribution and the ratio of factorial cumulants over factorial moments for 2-jet events in e+e- annihilation at the Z^0 peak can be well reproduced by the weighted superposition of two negative binomial distributions, associated to the contribution of $b\bar b$ and light flavoured events respectively. The negative binomial distribution is then suggested to describe the multiplicity distribution of 2-jet events with fixed flavour. 
Alberto Giovannini (Turin U. & INFN, Turin), Sergio Lupia (Munich, Max   Planck Inst.), Roberto Ugoccioni (Lund U.)