| Project Detail |
The fragmentation process is one of the most intriguing and poorly understood phenomenon of quantum chromodynamics (QCD). It belongs to the non-perturbative domain of QCD and is usually described by process-independent fragmentation functions (FFs). Traditionally, non-perturbative effects in the fragmentation process related to the quark-spin degree of freedom have been neglected and only recently their importance has been brought to light by the discovery of the Collins effect in transversely polarized quark jets. Such effect, described by a new spin-dependent FF, is a polarimeter for the transverse polarization of the quark initiating the jet and is presently used to access the partonic structure of nucleons. This project is dedicated to the study of the spin-dependence of the fragmentation process in the framework of the recent string+3P0 model, an extension of the Lund Model reproducing the Collins effect and other effects observed in fragmentation, to the development of the model, and to its implementation in the PYTHIA8 event generator for the simulation of the electron-positron annihilation process in hadrons. The end goal is the introduction of spin-effects in the polarized fragmentation of arbitrary string configurations originated from the parton showering process. The implementation of the string+3P0 model in the PYTHIA8 generator will be achieved by extending the StringSpinner package, which will be used for the phenomenological description of the spin-dependent observables measured in electron-positron annihilation. The proposed project will bring to new insights on the spin-dependence of the fragmentation process and to a practical open access MC event generator program acting as a theoretical laboratory for the study of this process. On a longer term, the project is expected to lay the foundation for the systematic introduction of spin effects in the PYTHIA8 generator for other collision processes as well. |
