Available plugins

The model produces fragmentation weights which are in turn used to perform a rejection sampling algorithm that modifies the Pythia fragmentation function. The final result are unweighted samples that follow a new fragmentation function determined by the ONNX model.

This allows the user to study the evolution of an observable with respect to the parton shower and, in particular, compute its IRC-safety in terms of the gradient of its entropy with respect to the evolution scale. Additionally, hadronization effects are also considered, allowing the user to compute the hadronization sensitivty of an observable in terms of the induced Fisher Information matrix over the hadronization parameters.

The color singlet system's produced by `Pythia8` as input to the Lund fragmentation model are, instead, passed to `Sherpa`. The path to the pre-build `Sherpa` library (lib, include, etc) must be provided. Currently, instructions on how to install `Sherpa` are not provided. The current implementation was done for git branch `rel-3-0-x` on `https://gitlab.com/sherpa-team/sherpa.git`.

The tool can be used to build template packages that can be used as part of the Pythia plugin system.

At the end of the parton shower, all gluons are split into quark-antiquark pairs carrying the large-N_c-limit color tags. Quarks and anti-quarks with matching color and anti-color tags are formed into color neutral clusters. These clusters subsequently undergo two-body decays to hadrons according to the given quantum numbers.