Evolution of average multiplicities of quark and gluon jets

TL;DR

This paper investigates how the average number of particles in quark and gluon jets changes with energy using advanced perturbative QCD calculations, highlighting the significance of higher order corrections and comparing with experimental data.

Contribution

It introduces third-order (3NLO) calculations for jet multiplicities and analyzes the sensitivity of various quantities to higher order and nonperturbative effects.

Findings

Gluon jets have higher average multiplicities than quark jets.

Gluon jets' multiplicities grow faster with energy.

Certain observables are more sensitive to higher order corrections.

Abstract

The energy evolution of average multiplicities of quark and gluon jets is studied in perturbative QCD. Higher order (3NLO) terms in the perturbative expansion of equations for the generating functions are found. First and second derivatives of average multiplicities are calculated. The mean multiplicity of gluon jets is larger than that of quark jets and evolves more rapidly with energy. It is shown which quantities are most sensitive to higher order perturbative and nonperturbative corrections. We define the energy regions where the corrections to different quantities are important. The latest experimental data are discussed.