Timelike Dipole-Antenna Showers with Massive Fermions

TL;DR

This paper develops a formalism for timelike dipole-antenna showers with massive fermions, compares it to fixed-order calculations and resummations, and implements it in PYTHIA 8 for experimental data analysis.

Contribution

It introduces a complete formalism for massive fermion showers, including implementation and validation against theoretical and experimental benchmarks.

Findings

Good agreement with fixed-order matrix elements up to Z to 6 partons

Consistent matching with analytical NLL resummations

Effective comparison to experimental data in b-tagged Z decays

Abstract

We present a complete formalism for final-state (timelike) dipole-antenna showers including fermion masses, but neglecting polarization and finite-width effects. We make several comparisons of tree-level expansions of this shower algorithm to fixed-order matrix elements for hadronic Z decays, up to and including Z to 6 partons, to which the algorithm can be consistently matched over all of phase space. We also compare to analytical resummations at the NLL level. The shower algorithm has been implemented in the publicly available VINCIA plugin to the PYTHIA 8 event generator, which enables us to compare to experimental data at the fully hadronized level. We also include comparisons to selected observables in b-tagged Z decays.