On the forward–backward correlations in a two-stage scenario

It is demonstrated that in a two-stage scenario with elementary Poissonian emitters of particles (colour strings) arbitrarily distributed in their number and average multiplicities, the forward–backward correlations are completely determined by the final distribution of forward particles. The observed linear form of the correlations then necessarily requires this distribution to have a negative binomial form. For emitters with a negative binomial distribution in the produced particles distributed so as to give the final distribution also of the negative binomial form, the forward–backward correlations have an essentially non-linear form which disagrees with the experimental data.