CompHEP 4.4 - Automatic Computations from Lagrangians to Events

TL;DR

The paper introduces CompHEP 4.4, a tool for automatic computations from Lagrangians to events, highlighting enhancements for multi-particle final states at colliders. Key innovations include quark flavor combinatorics simplification, color-flow treatment for shower/hadronization interfaces, LanHEP-based MSSM modeling, a robust CompHEP–PYTHIA interface, and new symbolic/numerical batch modes. It demonstrates practical application through the SingleTop generator, which achieves near-NLO consistency by combining LO matrix elements with real-emission corrections and spin correlations. The authors also outline future directions such as distributed Monte Carlo, FORM-based symbolic computations, and expanded Les Houches Accord interfaces for SUSY and PDFs, underscoring the framework's potential for efficient, accurate collider simulations.

Abstract

We present a new version of the CompHEP program (version 4.4). We describe shortly new issues implemented in this version, namely, simplification of quark flavor combinatorics for the evaluation of hadronic processes, Les Houches Accord based CompHEP-PYTHIA interface, processing the color configurations of events, implementation of MSSM, symbolical and numerical batch modes, etc. We discuss how the CompHEP program is used for preparing event generators for various physical processes. We mention a few concrete physics examples for CompHEP based generators prepared for the LHC and Tevatron.

Figures (3)

• Figure 1: Very incomplete list of processes computed by means of CompHEP in the past
• Figure 2: Scattering Topology (see the Figures for other topologies in Boos:2000ap)
• Figure 3: LO order and representative loop and tree NLO diagrams to the t-channel single top production