NGluon: A package to calculate one-loop multi-gluon amplitudes

Abstract

We present a computer library for the numerical evaluation of colour-ordered n-gluon amplitudes at oneloop order in pure Yang-Mills theory. The library uses the recently developed technique of generalised unitarity. Running in double precision the library yields reliable results for up to 14 gluons with only a small fraction of events requiring a re-evaluation using extended floating point arithmetic. We believe that the library presented here provides an important contribution to future LHC phenomenology. The program may also prove useful in cross checking results obtained by other methods. In addition, the code provides a sample implementation which may serve as a starting point for further developments. Program summary Program title: NGluonCatalogue identifier: AEIZ_v1_0 Program summary URL: Nature of problem: Evaluation of next-to-leading order corrections for gluon scattering amplitudes in pure gauge theory. Solution method: Purely numerical approach based on tree amplitudes obtained via Berends-Giele recursion combined with unitarity method. Restrictions: Running in double precision the number of gluons should not exceed 14. Running time: Depending on the number of external gluons between less than a millisecond (4 gluons) up to a 1 s (14 gluons) per phase space point.

Monodromy-like relations for finite loop amplitudes

“…At tree-level, old and new computational techniques have almost trivialized the computation of helicity amplitudes for any multiplicity [1][2][3][4]. Similarly, at the one-loop level highly-refined methods exists for determining amplitudes in massless theories [5][6][7][8]. The emergence of novel structures can have far-reaching consequences, potentially reshaping the way one organizes the theory beyond tree and one-loop level.…”

RECOLA2: REcursive Computation of One-Loop Amplitudes 2

“…The traditional as well as the new techniques for the calculation of oneloop amplitudes have been implemented in many codes such as FeynArts/ FormCalc [20][21][22], CutTools [23], Blackhat [24], Helac-1loop [13], NGluon [25], Samurai [26], Madloop [27], GoSam [28], and OpenLoops [14]. In this article we present the Fortran95 library Recola for the generation of tree-level and one-loop amplitudes in the SM.…”

Electroweak corrections to lepton pair production in association with two hard jets at the LHC

“…In the past years, many groups have concentrated their efforts to make NLO calculations feasible, and a lot of codes have been designed [3][4][5][6][7][8][9][10][11] with a high level of automatisation and impressive performances, however with their range of applicability mostly restricted to the QCD sector of the SM. For EW corrections, the situation is more involved and a complete automatisation has not been achieved yet, while different groups are working in this direction [12,13].…”