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11 papers found.
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Two-loop master integrals for the leading QCD corrections to the Higgs coupling to a W pair and to the triple gauge couplings ZW W and γ∗ W W

We compute the two-loop master integrals required for the leading QCD corrections to the interaction vertex of a massive neutral boson X 0, e.g. H, Z or γ∗, with a pair of W bosons, mediated by a SU(2) L quark doublet composed of one massive and one massless flavor. All the external legs are allowed to have arbitrary invariant masses. The Magnus exponential is employed to identify ...

Adaptive integrand decomposition in parallel and orthogonal space

We present the integrand decomposition of multiloop scattering amplitudes in parallel and orthogonal space-time dimensions, d = d ∥ + d ⊥, being d ∥ the dimension of the parallel space spanned by the legs of the diagrams. When the number n of external legs is n ≤ 4,thecorrespondingrepresentationofmultiloopintegralsexposesasubsetofintegration variables which can be easily integrated ...

Two-loop master integrals for the mixed EW-QCD virtual corrections to Drell-Yan scattering

We present the calculation of the master integrals needed for the two-loop QCD × EW corrections to \( q+\overline{q}\to {l}^{-}+{l}^{+} \) and \( q+\overline{q}^{\prime}\to {l}^{-}+\overline{\nu} \) , for massless external particles. We treat the W and Z bosons as degenerate in mass. We identify three types of diagrams, according to the presence of massive internal lines: the ...

Spin polarisation of \(t\bar{t}\gamma \gamma \) production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO

Eur. Phys. J. C Spin polarisation of t t¯γ γ production at NLO+PS with GOSAM interfaced to MADGRAPH5_AMC@NLO Hans van Deurzen 2 Rikkert Frederix 1 Valentin Hirschi 0 Gionata Luisoni 2 Pierpaolo ... Mastrolia 2 5 Giovanni Ossola 3 4 0 SLAC, National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, CA 94025-7090 , USA 1 Physik Department T31, Technische Universität München , James-Franck-Str

Three-loop master integrals for ladder-box diagrams with one massive leg

The three-loop master integrals for ladder-box diagrams with one massive leg are computed from an eighty-five by eighty-five system of differential equations, solved by means of Magnus exponential. The results of the considered box-type integrals, as well as of the tower of vertex- and bubble-type master integrals associated to subtopologies, are given as a Taylor series expansion ...

Multi-leg one-loop massive amplitudes from integrand reduction via Laurent expansion

We present the application of a novel reduction technique for one-loop scattering amplitudes based on the combination of the integrand reduction and Laurent expansion. We describe the general features of its implementation in the computer code Ninja, and its interface to GoSam. We apply the new reduction to a series of selected processes involving massive particles, from six to ...

Magnus and Dyson series for Master Integrals

We elaborate on the method of differential equations for evaluating Feynman integrals. We focus on systems of equations for master integrals having a linear dependence on the dimensional parameter. For these systems we identify the criteria to bring them in a canonical form, recently identified by Henn, where the dependence of the dimensional parameter is disentangled from the ...

GoSam-2.0: a tool for automated one-loop calculations within the Standard Model and beyond

We present the version 2.0 of the program package GoSam for the automated calculation of one-loop amplitudes. GoSam is devised to compute one-loop QCD and/or electroweak corrections to multi-particle processes within and beyond the Standard Model. The new code contains improvements in the generation and in the reduction of the amplitudes, performs better in computing time and ...

Automated one-loop calculations with GoSam

We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD ...

One-loop Higgs plus four gluon amplitudes: full analytic results

We consider one-loop amplitudes of a Higgs boson coupled to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of a complex field ϕ that couples to the self-dual field strengths and compute the one-loop corrections to the ϕ-NMHV amplitude, which contains one gluon of positive helicity whilst the remaining three have negative helicity. We use ...