Scattering Amplitudes with Open Loops

Abstract

We introduce a new technique to generate scattering amplitudes at one loop. Traditional tree algorithms, which handle diagrams with fixed momenta, are promoted to generators of loop-momentum polynomials that we call open loops. Combining open loops with tensor-integral and Ossola-Papadopoulos-Pittau reduction results in a fully flexible, very fast, and numerically stable one-loop generator. As demonstrated with nontrivial applications, the open-loop approach will permit us to obtain precise predictions for a very wide range of collider processes.

Triple Higgs boson production at a 100 TeV proton-proton collider

“…All tree-level and next-to-leading order (i.e. matched via the MC@NLO method [89]) background processes have been generated using MadGraph 5/aMC@NLO, apart from the di-Higgs plus jets (hh + jets) background, which was simulated using HERWIG++ in conjunction with the OpenLoops matrix-element generator [32,90]. The default parton density functions were used in each case: for the signal and tree-level backgrounds (including hh+jets) the NNPDF23 nlo as 0119 set was used, whereas for the NLO samples the NNPDF23 nlo as 0118 qed set was employed [91].…”

Higgs boson production in association with top quarks in the POWHEG BOX

“…Even though the background to ttH represents a major hurdle which needs to be overcome in order to properly measure this very important production channel, a very accurate control of the signal is still the first necessary step, and the possibility for the experimental community to have access to several public tools is very valuable. Our implementation answers this need and provides the original NLO-QCD analytic calculation [22][23][24][25] in the same framework (POWHEG BOX in this case) as other processes that enter the ttH studies, from tt production [41] to single-top production [42] or Higgs production in gluon-gluon fusion [43,44], offering a fully consistent alternative to analogous studies in the MadGraph5 aMC@NLO [45] and Open Loops [46] frameworks.…”

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].…”