Feynman rules for the rational part of the standard model one-loop amplitudes in the ’t Hooft-Veltman γ 5 scheme

6,211

5,572

We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations -parton-level fixed order, shower-matched, merged -in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

Section: Jhep07(2014)079mentioning

confidence: 99%

The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations

Alwall

Frederix

Frixione

et al. 2014

6,211

5,572

“…The missing (4 − D)-dimensional contributions-called R 2 rational terms-are universal and can be restored from process-independent effective counterterms [92][93][94]. Corresponding Feynman rules have been derived for QED in [92], for QCD in [95] and for the complete EW Standard Model in [96][97][98][99]. We implemented all QCD and EW R 2 counterterms in OpenLoops and validated them against independent algebraic results in D = 4 − 2 dimensions.…”

Section: Tree and One-loop Amplitudes With Openloopsmentioning

confidence: 99%

NLO electroweak automation and precise predictions for W + multijet production at the LHC

Kallweit

Lindert

Maierhöfer

et al. 2015

151

204

We present a fully automated implementation of next-to-leading order electroweak (NLO EW) corrections in the OpenLoops matrix-element generator combined with the Sherpa and Munich Monte Carlo frameworks. The process-independent character of the implemented algorithms opens the door to NLO QCD+EW simulations for a vast range of Standard Model processes, up to high particle multiplicity, at current and future colliders. As a first application, we present NLO QCD+EW predictions for the production of positively charged on-shell W bosons in association with up to three jets at the Large Hadron Collider. At the TeV energy scale, due to the presence of large Sudakov logarithms, EW corrections reach the 20-40% level and play an important role for searches of physics beyond the Standard Model. The dependence of NLO EW effects on the jet multiplicity is investigated in detail, and we find that W + multijet final states feature genuinely different EW effects as compared to the case of W + 1 jet.

“…For both models, the R 2 rules have been taken from refs. [55][56][57]. In view of the complexity of the models, all counterterms have been cross-checked with an independent Mathematica package.…”

Section: Calculation Of the O(αmentioning

confidence: 99%

Weak corrections to Higgs hadroproduction in association with a top-quark pair

Frixione

Hirschi

Pagani

et al. 2014

120

129

We present the calculation of the next-to-leading contribution of order α 2 S α 2 to the production of a Standard Model Higgs boson in association with a top-quark pair at hadron colliders. All effects of weak and QCD origin are included, whereas those of QED origin are ignored. We work in the MadGraph5 aMC@NLO framework, and discuss sample phenomenological applications at a 8, 13, and 100 TeV pp collider, including the effects of the dominant next-to-leading QCD corrections of order α 3 S α.