Overview of hadronization of quarks in proton-proton and e⁺e⁻ collisions

¹ University of Trieste, Italy
² INFN Trieste, Italy

^* e-mail: mfaggin@cern.ch

Published online: 16 February 2024

Abstract

The so-called hadronization is a non-perturbative QCD phenomenon corresponding to the formation of colourless hadrons from coloured quark con stituents. The hadron formation in point-like e⁺e⁻ collisions can be described by string models. According to the Lund model, the qq¯ pair production in the scattering is followed by a shower of light partons produced via multiple colour-string breaking, which produce colour singlets in the final states. The probability to obtain a hadron of a given species carrying a certain momentum fraction of the original quark is quantified by the fragmentation functions. They are assumed universal and usually constrained from e⁺ e⁻ and e⁻p collisions, and they successfully describe the production of mesons in e⁺e⁻ and pp colli sions at the colliders. However, recent measurements of pp collision data from the LHC showed a surprising relative enhancement of baryon production com pared to mesons, and model predictions based on string fragmentation do not describe the data. In this talk, an overview of the most recent experimental re sults of hadron production cross section in pp collisions at the LHC compared with e⁺e⁻ results will be provided. A comparison with novel theoretical models implementing hadronization mechanisms different from the Lund string frag mentation will be also discussed, as well as experimental results obtained in larger systems, like p–Pb and Pb–Pb collisions.