Medium dependence of multiplicity distributions in MLLA

TL;DR

This paper investigates how a QCD medium affects multiplicity distributions in MLLA, revealing opposite dispersion behaviors depending on whether the anomalous dimension or the coupling is held fixed.

Contribution

It introduces a medium modification in the QCD evolution equations and compares the effects under different fixed parameters, providing new insights into medium dependence.

Findings

Dispersion decreases with medium strength when fixing gamma.

Dispersion increases with medium strength when fixing alpha_s.

Opposite behaviors are observed depending on the fixed parameter choice.

Abstract

We study the modification of the multiplicity distributions in MLLA due to the presence of a QCD medium. The medium is introduced though a multiplicative constant ($f_{med}$) in the soft infrared parts of the kernels of QCD evolution equations. Using the asymptotic ansatz for quark and gluons mean multiplicities $<n_G>=e^{\gamma y}$ and $<n_Q>=r^{-1}e^{\gamma y}$ respectively, we study two cases: fixed $\gamma$ as previously considered in the literature, and fixed $\alpha_s$. We find opposite behaviors of the dispersion of the multiplicity distributions with increasing $f_{med}$ in both cases. For fixed $\gamma$ the dispersion decreases, while for fixed $\alpha_s$ it increases.