Next-to-leading order W + 5 -jet production at the LHC

6,050

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

6,050

5,572

“…in (4.2) factorizes as 6) with n µ a light-like vector, n 2 = 0. Similarly, in the limit where p ′ i and p ′ r become collinear the tree-level matrix element M (0), ir N +1 factorizes as…”

Section: Jhep11(2014)014mentioning

confidence: 99%

“…the SM and beyond, has shown an extraordinary progress in the recent years. Today, 2 → 4 processes at next-to-leading order (NLO) are state of the art [1][2][3][4][5], and even higher multiplicities are affordable [6]. Several tools for the automated calculation of NLO differential cross sections are available [7,8], including the merging with parton showers [9].…”

Section: Introductionmentioning

confidence: 99%

On the singular behaviour of scattering amplitudes in quantum field theory

Buchta

Chachamis

Draggiotis

et al. 2014

Abstract:We analyse the singular behaviour of one-loop integrals and scattering amplitudes in the framework of the loop-tree duality approach. We show that there is a partial cancellation of singularities at the loop integrand level among the different components of the corresponding dual representation that can be interpreted in terms of causality. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences.

“…The q T spectrun of the diphoton pair has been calculated in fully-differential Monte Carlo codes at LO [13][14][15][16] and at NLO [23][24][25]. Recently, first calculations for diphoton production in association with two [26][27][28] and three [28] jets at NLO became available.…”

Section: Jhep06(2015)185mentioning

confidence: 99%

Diphoton production at hadron colliders: transverse-momentum resummation at next-to-next-to-leading logarithmic accuracy

Cieri

Coradeschi

Florian

2015

Abstract:We consider the transverse-momentum (q T ) distribution of a diphoton pair produced in hadron collisions. At small values of q T , we resum the logarithmically-enhanced perturbative QCD contributions up to next-to-next-to-leading logarithmic accuracy. At intermediate and large values of q T , we consistently combine resummation with the known next-to-leading order perturbative result. All perturbative terms up to order α 2 S are included in our computation which, after integration over q T , reproduces the known nextto-next-to-leading order result for the diphoton pair production total cross section. We present a comparison with LHC data and an estimate of the perturbative accuracy of the theoretical calculation by performing the corresponding variation of scales. In general we observe that the effect of the resummation is not only to recover the predictivity of the calculation at small transverse momentum, but also to improve substantially the agreement with the experimental data.