Golem95C: A library for one-loop integrals with complex masses

Abstract

We present a program for the numerical evaluation of scalar integrals and tensor form factors entering the calculation of one-loop amplitudes which supports the use of complex masses in the loop integrals. The program is built on an earlier version of the golem95 library, which performs the reduction to a certain set of basis integrals using a formalism where inverse Gram determinants can be avoided. It can be used to calculate one-loop amplitudes with arbitrary masses in an algebraic approach as well as in the context of a unitarity-inspired numerical reconstruction of the integrand.Comment: 22 pages, 3 figure

HW ±/HZ + 0 and 1 jet at NLO with the POWHEG BOX interfaced to GoSam and their merging within MiNLO

“…When integrating over the phase space, the virtual matrix elements are evaluated with SAMURAI [28] or, alternatively, with Golem95 [29]. The first program evaluates the amplitude using integrand reduction methods [30] extended to D-dimensions [31], whereas the latter allows to compute the same amplitude evaluating tensor-integrals.…”

“…The interplay of the two reduction strategies is used to guarantee the highest speed for the produced codes, while keeping the required precision for good numerical stability of the results. For the evaluation of the scalar one-loop integrals QCDLoop [32,33], OneLOop [34] or Golem95C [29] can be used.…”

RECOLA2: REcursive Computation of One-Loop Amplitudes 2

“…For the evaluation of the one-loop integrals, a task that demands high standards with respect to numerical stability and CPU performance, amplitude generators are either equipped with own internal implementations, or they rely on external libraries like FF [36], LoopTools [37], QCDLoop [38], OneLOop [39], Golem95C [40], PJFry [41], Package-X [42], and Collier [43,44]. In the case of Recola, the public Fortran95 library Collier is used which achieves a fast and stable calculation of tensor integrals via the strategies developed in Refs.…”

A novel method to compute one loop 4 point functions

“…This method extends rather easily to the case where there are collinear/soft divergences. The results of all these formula have been coded into a FORTRAN 95 program and checked against the existing results [4], [9].…”