Implementation of supersymmetric processes in the HERWIG event generator

TL;DR

This paper documents the integration of supersymmetry into the HERWIG event generator, adopting a general MSSM framework with optional R-parity violation and a completely general sparticle spectrum. It specifies parameter and mixing conventions, including careful translations between common formalisms (Haber-Gunion, Baer) and ISAJET inputs via ISAWIG, and provides an exhaustive set of hard-scattering matrix elements for 2→2, 2→1, and 2→3 processes across hadron-hadron and lepton-lepton collisions. R-parity conserving and violating production channels are implemented, with spin correlations and beam polarization, and decay matrix elements cover both two- and three-body decays. The work delivers a practical, comprehensive framework enabling realistic SUSY event generation in collider simulations, integrating with existing SM physics and allowing user-driven spectra from data files. Overall, it expands HERWIG’s applicability to SUSY phenomenology and LHC-era analyses by providing detailed, validated matrix elements and robust interfaces for MSSM parameter inputs.

Abstract

We describe the implementation of supersymmetric processes in the HERWIG Monte Carlo event generator. We define relevant parameter and mixing conventions and list the hard scattering matrix elements. Our implementation is based on the Minimum Supersymmetric Standard Model, with the option of R-parity violation. The sparticle spectrum is completely general. Both hadron-hadron and lepton-lepton collisions are covered. This article supplements a separate publication in which the general features of HERWIG 6.2 are described, and updates the treatment of supersymmetry to version 6.4.