HELAS and MadGraph with goldstinos

TL;DR

This paper introduces Fortran subroutines for calculating helicity amplitudes involving goldstinos, enabling automatic generation of such amplitudes in MadGraph, with applications to gravitino production cross sections.

Contribution

It adds new subroutines to the HELAS library for goldstinos, allowing seamless integration with MadGraph for high-energy physics simulations.

Findings

Validated the codes using goldstino equivalence theorem

Ensured gauge invariance of helicity amplitudes

Presented cross sections for gravitino production processes

Abstract

Fortran subroutines to calculate helicity amplitudes with goldstinos, which appear as the longitudinal modes of massive gravitinos in high energy processes, are added to the HELAS (HELicity Amplitude Subroutines) library. They are coded in such a way that arbitrary amplitudes with external goldstinos can be generated automatically by MadGraph, after slight modifications. All the codes have been tested carefully by making use of the goldstino equivalence theorem and the gauge invariance of the helicity amplitudes. Hadronic total cross sections for associated gravitino productions with a gluino and a squark are also presented.