AMEGIC++ 1.0, A Matrix Element Generator In C++

TL;DR

The paper addresses the computational bottleneck of multi-particle production in high-energy collisions by introducing AMEGIC++ 1.0, a matrix-element generator that automatically produces tree-level helicity amplitudes and translates them into optimized C++ libraries.It combines a robust helicity formalism with a multi-channel phase-space integration strategy (including RAMBO and SARGE) to efficiently navigate the high-dimensional, highly resonant integration landscape.A comprehensive implementation is described, covering diagram generation, helicity translation, color and Coulomb corrections, string-based algebraic representations, and phase-space channel construction, with extensive class-level descriptions and a complete installation/running guide.The approach significantly improves evaluation efficiency by precomputing and compiling amplitudes into libraries and by tailoring integration channels to the singular structure of each diagram, enabling practical studies of complex multi-jet processes and providing a foundation for future model extensions.

Abstract

The new matrix element generator AMEGIC++ is introduced, dedicated to describe multi-particle production in high energy particle collisions. It automatically generates helicity amplitudes for the processes under consideration and constructs suitable, efficient integration channels for the multi-channel phase space integration. The corresponding expressions for the amplitudes and the integrators are stored in library files to be linked to the main program.

Figures (19)

• Figure 1: Three boson vertices available within AMEGIC++. Note that all boson lines might be on-- or off--shell. Scalar and vector bosons are depicted as dotted and wavy lines, respectively, whereas a gluon is marked by a curly line.
• Figure 2: Four boson vertices available within AMEGIC++. Note that all boson lines might be on-- or off--shell. Scalar and vector bosons are depicted as dotted and wavy lines, respectively, whereas a gluon is marked by a curly line.
• Figure 3: Five gluon vertex available within AMEGIC++. Note that all boson lines might be on-- or off--shell.
• Figure 4: Scalar propagators can be cut easily. Scalar and vector bosons are depicted as dotted and wavy lines, respectively.
• Figure 5: Diagrams related to the Coulomb correction as implemented within AMEGIC++.