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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 derive a compact expression for the three-point MHV form factors of half-BPS operators in N=4 super Yang-Mills at two loops. The main tools of our calculation are generalised unitarity applied at the form factor level, and the compact…

High Energy Physics - Theory · Physics 2015-06-03 Andreas Brandhuber , Gabriele Travaglini , Gang Yang

In this lecture we summarize recent calculations pointing to the possible ultraviolet finiteness of N = 8 supergravity in four dimensions. We outline the modern unitarity method, which enables multiloop calculations in this theory and…

High Energy Physics - Theory · Physics 2009-03-02 Z. Bern , J. J. M. Carrasco , H. Johansson

We present a description for amplitude diagrams in maximal supergravities obtained by dimensional reduction from D=11, derived from a field theory point of view using the pure spinor formalism. The advantages of this approach are the…

High Energy Physics - Theory · Physics 2015-06-12 Martin Cederwall , Anna Karlsson

We present a new method for computing multi-loop scattering amplitudes in Quantum Field Theory. It extends the Generalized Unitarity method by constraining not only the integrand of the amplitude but also its full integrated form. Our…

High Energy Physics - Theory · Physics 2025-12-18 Piotr Bargiela

We provide a leading singularity analysis protocol in Baikov representation, for the searching of Feynman integrals with uniform transcendental (UT) weight. This approach is powered by the recent developments in rationalizing square roots…

High Energy Physics - Theory · Physics 2021-08-18 Christoph Dlapa , Xiaodi Li , Yang Zhang

We obtain a color-kinematics-dual representation of the two-loop four-vector amplitude a general renormalizable massless $\mathcal{N}=1$ SYM theory, including internal matter as chiral supermultiplets. The integrand is constructed to be…

High Energy Physics - Theory · Physics 2023-12-29 Henrik Johansson , Gregor Kälin , Gustav Mogull , Bram Verbeek

We present compact formulas for the box coefficients of the six-point NMHV one-loop amplitudes in N=8 supergravity. We explicitly demonstrate that the corresponding box integral functions, with these coefficients, have the complete IR…

High Energy Physics - Theory · Physics 2011-09-29 N. E. J. Bjerrum-Bohr , David C. Dunbar , Harald Ita

We present the complete four-loop four-point amplitude in N=4 super-Yang-Mills theory, for a general gauge group and general D-dimensional covariant kinematics, and including all non-planar contributions. We use the method of maximal cuts…

High Energy Physics - Theory · Physics 2011-03-03 Z. Bern , J. J. M. Carrasco , L. J. Dixon , H. Johansson , R. Roiban

We extend the generalized D-dimensional unitarity method for numerical evaluation of one-loop amplitudes by incorporating massive particles. The issues related to extending the spinor algebra to higher dimensions, treatment of external…

High Energy Physics - Phenomenology · Physics 2010-04-21 R. K. Ellis , W. T. Giele , Z. Kunszt , K. Melnikov

In this work, we present an algorithm for the diagonalization of the Integration-by-Parts (IBP) equations. Diagonalized IBP equations are indispensable for reducing loop integrals with high numerator powers to master integrals and for…

High Energy Physics - Phenomenology · Physics 2025-12-08 Junhan W. Liu , Alexander Mitov

We solve the integration-by-parts (IBP) identities needed for the computation of any planar two-loop five-point massless amplitude in QCD. We also derive some new results for the most complicated non-planar topology with irreducible…

High Energy Physics - Phenomenology · Physics 2019-08-13 Herschel A. Chawdhry , Matthew A. Lim , Alexander Mitov

During the last several years remarkable progress has been made in numerical calculations of dimensionally regulated multi-loop Feynman diagrams using Mellin-Barnes (MB) representations. The bottlenecks were non-planar diagrams and…

High Energy Physics - Phenomenology · Physics 2017-08-02 Ievgen Dubovyk , Janusz Gluza , Tomasz Jelinski , Tord Riemann , Johann Usovitsch

Though the one-loop amplitudes of the Higgs boson to massless gauge bosons are finite because there is no direct interaction at tree-level in the Standard Model, a well-defined regularization scheme is still required for their correct…

High Energy Physics - Phenomenology · Physics 2018-03-22 Felix Driencourt-Mangin , German Rodrigo , German F. R. Sborlini

Two-loop multi-leg form factors in off-shell kinematics require knowledge of planar and nonplanar double box Feynman diagrams with massless internal propagators. These are complicated functions of Mandelstam variables and external particle…

High Energy Physics - Theory · Physics 2024-02-29 A. V. Belitsky , V. A. Smirnov

We study 1-loop MHV amplitudes in N=4 super Yang-Mills theory and in N=8 supergravity. For Yang-Mills we find that the simple form for the full amplitude presented by Del Duca, Dixon and Maltoni naturally leads to one that has physical…

High Energy Physics - Theory · Physics 2013-05-23 Ellis Ye Yuan

We study the three-loop four-point amplitude in ABJM theory. We determine the dual conformal invariant integrals with highest number of propagators and fix their coefficients by two-particle cuts. Evaluating such a combination of integrals…

High Energy Physics - Theory · Physics 2015-06-19 Marco S. Bianchi , Matias Leoni

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 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

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…

High Energy Physics - Phenomenology · Physics 2015-06-22 Stefano Di Vita , Pierpaolo Mastrolia , Ulrich Schubert , Valery Yundin