StringSpinner -- adding spin to the PYTHIA string fragmentation

TL;DR

StringSpinner enhances the PYTHIA 8 event generator by incorporating spin effects into hadronization, enabling simulation of polarized processes using the string+${}^3P_0$ model and transversity PDFs.

Contribution

It introduces a plugin for PYTHIA 8 that models spin effects during hadronization, allowing for polarized process simulations with customizable transversity distributions.

Findings

Simulated Collins asymmetries in polarized SIDIS.

Demonstrated how to modify transversity parametrizations.

Validated spin propagation in the string fragmentation model.

Abstract

StringSpinner is a plugin for the introduction of the spin effects in the hadronization part of the PYTHIA 8 event generator. The spin effects are generated for pseudoscalar meson production by propagating the quark polarization along the fragmentation chain according to the rules of the quantum mechanical string+${}^3P_0$ model. By using parametrizations for the transversity parton distribution functions, StringSpinner allows to simulate the polarized semi inclusive deep inelastic scattering process on protons and neutrons. The instructions to use StringSpinner and to modify the parametrizations of the transversity distribution functions are presented, as well as an example of the calculation of the Collins asymmetries as obtained from simulations of the transversely polarized semi inclusive deep inelastic scattering process.