Multiplicity distribution and entropy of produced gluons in deep inelastic scattering at high energies

Abstract: In this paper we found the multiplicity distribution of the produced gluons in deep inelastic scattering at large $z=\ln\LbQ^2_s/Q^2\Rb\,\,\gg\,\,1$ where $ Q_s $ is the saturation momentum and $Q^2$ is the photon virtuality. It turns out that this distribution at large $n > \bar{n}$ almost reproduces the KNO scaling behaviour with the average number of gluons $ \bar{n} \propto \exp\Lb z^2/2 \kappa\Rb$, where $\kappa = 4.88 $ in the leading order of perturbative QCD. TheKNO function $\Psi\Lb \frac{n}{\bar{n}}\Rb = \exp\Lb -\,n/\bar{n}\Rb$. For $n < \bar{n}$ we found that $\sigma_n \propto\Big( z - \sqrt{2 \,\kappa\,\ln (n-1)}\Big)/(n-1)$. Such small $n$ determine the value of entropy of produced gluons $S_E = 0.3\, z^2/(2\,\kappa)$ at large $z$. The factor $0.3$ stems from the non-perturbative corrections that provide the correct behaviour of the saturation momentum at large $b$.