Hadronization
Bryan Webber
TL;DR
This review assesses how hadronization modifies perturbative QCD predictions, detailing three main model families (independent fragmentation, string, cluster) and their integration into event generators, to explain data from $e^+e^-$ and DIS. It highlights a robust pattern of $1/Q$ power corrections for infrared-safe observables like event shapes and the role of coherence and small-$x$ dynamics in jet fragmentation, framed in part by infrared renormalon ideas. The paper also discusses fragmentation functions, their Altarelli–Parisi evolution, and the extraction of gluon fragmentation from longitudinal observables, connecting experimental results at LEP and HERA with theoretical expectations. Overall, it argues that hadronization corrections are substantial and theoretically intricate, necessitating both refined models and higher-order perturbative calculations for precise QCD tests and $\alpha_s$ determinations.
Abstract
Hadronization corrections to the predictions of perturbative QCD are reviewed. The existing models for the conversion of quarks and gluons into hadrons are summarized. The most successful models give a good description of the data on $e^+e^-$ event shapes and jet fragmentation functions, and suggest that the dominant hadronization effects have a $1/Q$ dependence on the hard process energy scale $Q$. In several cases the $1/Q$ terms can be understood in terms of a simple longitudinal phase-space model. They can also be inferred by relating non-perturbative renormalon effects to the infrared cutoff dependence of perturbative contributions.