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We describe the unitarity approach for the numerical computation of two-loop integral coefficients of scattering amplitudes. It is well known that the leading propagator singularities of an amplitude's integrand are related to products of…

High Energy Physics - Phenomenology · Physics 2017-06-07 S. Abreu , F. Febres Cordero , H. Ita , M. Jaquier , B. Page

The overall coefficient of the two-loop 4-particle amplitude in superstring theory is determined by making use of the factorization and unitarity. To accomplish this we computed in detail all the relevant tree and one-loop amplitudes…

High Energy Physics - Theory · Physics 2009-11-11 Zhi-Guang Xiao , Chuan-Jie Zhu

We propose new formulae for the two-loop n-point D-dimensional integrands of scattering amplitudes in Yang-Mills theory and gravity. The loop integrands are written as a double-forward limit of tree-level trivalent diagrams, and are…

High Energy Physics - Theory · Physics 2020-01-29 Yvonne Geyer , Ricardo Monteiro , Ricardo Stark-Muchão

We use the recently developed generalized double-copy procedure to construct an integrand for the five-loop four-point amplitude of N=8 supergravity. This construction starts from a naive double copy of the previously computed corresponding…

High Energy Physics - Theory · Physics 2017-12-27 Zvi Bern , John Joseph M. Carrasco , Wei-Ming Chen , Henrik Johansson , Radu Roiban , Mao Zeng

Calculation of amplitudes in perturbative quantum field theory involve large loop integrals. The complexity of those integrals, in combination with the large number of Feynman diagrams, make the calculations very difficult. Reduction…

High Energy Physics - Phenomenology · Physics 2015-06-05 Ronald H. P. Kleiss , Ioannis Malamos , Costas G. Papadopoulos , Rob Verheyen

We present the integrand decomposition of multiloop scattering amplitudes in parallel and orthogonal space-time dimensions, $d=d_\parallel+d_\perp$, being $d_\parallel$ the dimension of the parallel space spanned by the legs of the…

High Energy Physics - Phenomenology · Physics 2016-09-21 Pierpaolo Mastrolia , Tiziano Peraro , Amedeo Primo

Loop amplitudes are conveniently expressed in terms of master integrals whose coefficients carry the process dependent information. Similarly before integration, the loop integrands may be expressed as a linear combination of propagator…

High Energy Physics - Theory · Physics 2016-12-28 Harald Ita

The dual formulation of planar N = 4 super-Yang-Mills scattering amplitudes makes manifest that the integrand has only logarithmic singularities and no poles at infinity. Recently, Arkani-Hamed, Bourjaily, Cachazo and Trnka conjectured the…

High Energy Physics - Theory · Physics 2016-02-02 Zvi Bern , Enrico Herrmann , Sean Litsey , James Stankowicz , Jaroslav Trnka

We develop an iterative method for constructing four-dimensional generalized unitarity cuts in $\mathcal{N} = 2$ supersymmetric Yang-Mills (SYM) theory coupled to fundamental matter hypermultiplets ($\mathcal{N} = 2$ SQCD). For iterated…

High Energy Physics - Theory · Physics 2019-10-08 Gregor Kälin , Gustav Mogull , Alexander Ochirov

The self-duality of the N=1 supersymmetric Born--Infeld action implies a double self-duality of the tensor multiplet square-root action when the scalar and the antisymmetric tensor are interchanged via Poincare' duality. We show how this…

High Energy Physics - Theory · Physics 2015-06-11 S. Ferrara , A. Sagnotti , A. Yeranyan

We present an expression for the leading-color (planar) four-loop four-point amplitude of N=4 supersymmetric Yang-Mills theory in 4-2 e dimensions, in terms of eight separate integrals. The expression is based on consistency of unitarity…

High Energy Physics - Theory · Physics 2008-11-26 Zvi Bern , Michael Czakon , Lance J. Dixon , David A. Kosower , Vladimir A. Smirnov

We review some recent additions to the tool-chest of techniques for finding compact integrand representations of multiloop gauge-theory amplitudes - including non-planar contributions - applicable for N=4 super-Yang-Mills in four and higher…

High Energy Physics - Theory · Physics 2015-05-27 John Joseph M. Carrasco , Henrik Johansson

We present a method to compute the integrands of one-loop Einstein-Yang-Mills amplitudes for any number of external gauge and gravity multiplets. Our construction relies on the double-copy structure of Einstein-Yang-Mills as…

High Energy Physics - Theory · Physics 2023-03-01 Franziska Porkert , Oliver Schlotterer

We present an ansatz for all one-loop amplitudes in pure Einstein gravity for which the n external gravitons have the same outgoing helicity. These loop amplitudes, which are rational functions of the momenta, also arise in the quantization…

High Energy Physics - Theory · Physics 2010-11-15 Z. Bern , L. Dixon , M. Perelstein , J. S. Rozowsky

Supersymmetric integrands for the two-loop five-point amplitudes in ten-dimensional super Yang--Mills and type II supergravity are proposed. The kinematic numerators are manifestly local and satisfy the duality between color and kinematics…

High Energy Physics - Theory · Physics 2015-11-05 Carlos R. Mafra , Oliver Schlotterer

The spinor-helicity formalism has proven to be very efficient in the calculation of scattering amplitudes in quantum field theory, while the loop tree duality (LTD) representation of multi-loop integrals exhibits appealing and interesting…

High Energy Physics - Phenomenology · Physics 2021-01-27 Felix Driencourt-Mangin , German Rodrigo , German F. R. Sborlini , William J. Torres Bobadilla

We review recent progress in D-dimensional integrand reduction algorithms for two loop amplitudes and give examples of their application to non-planar maximal cuts of the five-point all-plus helicity amplitude in QCD.

High Energy Physics - Phenomenology · Physics 2014-07-14 Simon Badger , Hjalte Frellesvig , Yang Zhang

We derive the four-dimensional integrand of the maximal-helicity-violating four-particle form factor for the chiral part of the stress-tensor supermultiplet in planar $\mathcal{N}=4$ super-Yang-Mills theory at two loops. In our integrand…

High Energy Physics - Theory · Physics 2023-06-26 Tushar Gopalka , Enrico Herrmann

In this paper we extend the study initiated in arXiv:2302.04709v2 [hep-th] to the computation of one-loop elastic amplitudes. We consider 1+1 dimensional massive bosonic Lagrangians with polynomial-like potentials and absence of inelastic…

High Energy Physics - Theory · Physics 2024-03-08 Matheus Fabri , Davide Polvara

The causal representation of multi-loop scattering amplitudes, obtained from the application of the loop-tree duality formalism, comprehensively elucidates, at integrand level, the behaviour of only physical singularities. This…

High Energy Physics - Phenomenology · Physics 2021-06-23 William J. Torres Bobadilla