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We detail the calculation of two-loop all-plus helicity amplitudes for pure Yang-Mills theory. The four dimensional unitarity methods and augmented recursion techniques we have developed, together with a knowledge of the singular structure…

High Energy Physics - Theory · Physics 2017-12-27 David C. Dunbar , John H. Godwin , Guy R. Jehu , Warren B. Perkins

We present the two-loop helicity amplitudes for the scattering of massless quarks in QCD. We use projector techniques to compute the coefficients of the general four-quark amplitude at up to two-loops in conventional dimensional…

High Energy Physics - Phenomenology · Physics 2009-11-10 E. W. N. Glover

We provide results for the one-loop triple-collinear color/spin-space splitting operators for the five possible processes, $q \to qq'\bar{q}'$, $q \to qq\bar{q}$, $q \to qgg$, $g \to gq\bar{q}$ and $g \to ggg$. The expressions are exact in…

High Energy Physics - Phenomenology · Physics 2022-07-11 Michał Czakon , Sebastian Sapeta

We compute the helicity amplitudes for the processes $gg\to Zg$ and $gg\to Z\gamma$ to two loops in massless QCD. The perturbative expansion of these processes starts only at the one-loop level, such that our results are a crucial…

High Energy Physics - Phenomenology · Physics 2023-08-21 Thomas Gehrmann , Lorenzo Tancredi , Erich Weihs

We describe the recently developed on-shell bootstrap for computing one-loop amplitudes in non-supersymmetric theories such as QCD. The method combines the unitarity method with loop-level on-shell recursion. The unitarity method is used to…

High Energy Physics - Phenomenology · Physics 2008-11-26 Carola F. Berger , Zvi Bern , Lance J. Dixon , Darren Forde , David A. Kosower

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 phi that couples to the self-dual field strengths and compute the one-loop…

High Energy Physics - Phenomenology · Physics 2010-01-22 Simon Badger , E. W. Nigel Glover , Pierpaolo Mastrolia , Ciaran Williams

We complete the computation of two-loop helicity amplitudes required to obtain next-to-next-to-leading order QCD corrections for three-jet production at hadron colliders, including all contributions beyond the leading-color approximation.…

High Energy Physics - Phenomenology · Physics 2024-05-15 Giuseppe De Laurentis , Harald Ita , Vasily Sotnikov

We compute the one-loop amplitude for a Higgs boson, a quark-antiquark pair and a pair of gluons of negative helicity, i.e. for the next-to-maximally helicity violating (NMHV) case, A(H, qbar-, q+, g-, g-). The calculation is performed…

High Energy Physics - Phenomenology · Physics 2009-12-17 Simon Badger , John M. Campbell , R. Keith Ellis , Ciaran Williams

The numerical unitarity approach has been important for obtaining reliable QCD predictions for the LHC. Here I discuss the extension of the approach beyond the leading quantum corrections for computing multi-loop amplitudes. The numerical…

High Energy Physics - Phenomenology · Physics 2017-03-27 Harald Ita

In this talk we discuss a purely numerical approach to next-to-leading order calculations in QCD. We present a simple formula, which provides a local infrared subtraction term for the integrand of a one-loop amplitude. In addition we…

High Energy Physics - Phenomenology · Physics 2010-12-13 M. Assadsolimani , S. Becker , Ch. Reuschle , S. Weinzierl

The two-loop QCD corrections to vector boson pair production at hadron colliders involve a new class of Feynman integrals: two-loop four-point functions with two off-shell external legs. We describe their reduction to a small set of master…

High Energy Physics - Phenomenology · Physics 2013-08-26 Thomas Gehrmann , Lorenzo Tancredi , Erich Weihs

Loop calculations involve the evaluation of divergent integrals. Usually [1] one computes them in a number of dimensions different than four where the integral is convergent and then one performs the analytical continuation and considers…

High Energy Physics - Phenomenology · Physics 2009-10-31 Francesco Caravaglios

Many search strategies for the Standard Model Higgs boson apply specific selection criteria on hadronic jets observed in association with the Higgs boson decay products, either in the form of a jet veto, or by defining event samples…

High Energy Physics - Phenomenology · Physics 2015-06-03 T. Gehrmann , M. Jaquier , E. W. N. Glover , A. Koukoutsakis

One-loop amplitudes of gluons in supersymmetric Yang-Mills are four-dimensional cut-constructible. This means that they can be determined from their unitarity cuts. We present a new systematic procedure to explicitly carry out any finite…

High Energy Physics - Phenomenology · Physics 2009-07-09 Ruth Britto , Evgeny Buchbinder , Freddy Cachazo , Bo Feng

We propose an approach to compute one-loop corrections to the four-point amplitude in the higher spin gravities that are holographically dual to free $O(N)$, $U(N)$ and $USp(N)$ vector models. We compute the double-particle cut of one-loop…

High Energy Physics - Theory · Physics 2020-01-29 Dmitry Ponomarev , Ergin Sezgin , Evgeny Skvortsov

The four-loop QCD corrections to the electroweak $\rho$-parameter arising from top and bottom quark loops are computed. Specifically we evaluate the missing ``non-singlet'' piece. Using algebraic methods the amplitude is reduced to a set of…

High Energy Physics - Phenomenology · Physics 2008-11-26 K. G. Chetyrkin , M. Faisst , J. H. Kühn , P. Maierhoefer , C. Sturm

The unitarity method for calculating one-loop amplitudes provides algorithms of polynomial complexity. This is primarily beneficial for the computation of multi-leg one loop amplitudes and it is therefore of great interest to develop a…

High Energy Physics - Phenomenology · Physics 2009-04-14 R. Keith Ellis , Walter T. Giele , Zoltan Kunszt

The calculation of hard scattering amplitudes up to NLO is automated in numerical tools, such as OpenLoops. The LHC and future experiments, however, demand high-precision predictions at NNLO and beyond for a wide range of particle…

High Energy Physics - Phenomenology · Physics 2024-12-20 Natalie Schär , Max F. Zoller

We perform analytical reductions of one-loop tensor integrals with 5 and 6 legs to scalar master integrals. They are based on the use of recurrence relations connecting integrals in different space-time dimensions. The reductions are…

High Energy Physics - Phenomenology · Physics 2008-11-26 T. Diakonidis , J. Fleischer , J. Gluza , K. Kajda , T. Riemann , J. B. Tausk

Light cone perturbation theory has become an essential tool to calculate cross sections for various small-$x$ dilute-dense processes such as deep inelastic scattering and forward proton-proton and proton-nucleus collisions. Here we set out…

High Energy Physics - Phenomenology · Physics 2017-04-05 Tuomas Lappi , Risto Paatelainen