One-loop multi-leg calculations in gauge theories: the Golem library

I present a program designed for the numerical evaluation of one-loop multi-leg scattering amplitudes. This program, called Golem95 , is written in FORTRAN-95 , and it contains all the form factors involved in one-loop calculations of amplitudes with up to six external legs, for arbitrary internal masses (complex masses are supported). This library is based on the traditional algebraic reduction (Golem reduction) of the form factors into a certain redundant set of basis integrals; this reduction formalism is able to avoid the problem of the Gram determinant spurious singularity. Golem95 can be used to calculate one-loop amplitudes in the framework of an algebraic reduction approach, as well as in the framework of inspired- unitarity reconstruction of the amplitudes ( GoSam ) [ 1 ].