Master integrals for e+e− → 2γ process at large energies and angles

We calculate the first Coulomb correction to the spectra of two processes: the electron bremsstrahlung and electron-positron photoproduction in the Coulomb field. We show that, in contrast to the results obtained in the Born approximation and in the high-energy limit, the obtained corrections for these two process are not related by the crossing symmetry substitutions. The found corrections determine the leading contribution to the charge asymmetry in these processes. We use modern multiloop methods based on the IBP reduction and on the differential equations for master integrals. The results are presented in terms of classical polylogarithms. We provide both the threshold and the high-energy asymptotics of the obtained expressions and compare them with available results.

We compute the master integrals for the two-loop QCD corrections to quark quasi parton distribution functions (PDFs) in the large momentum effective theory (LaMET). With a proper canonical basis, we derive the analytical results for the three families of master integrals using the method of differential equations. The final expressions for the master integrals are given in terms of Goncharov polylogarithms. These results allow us to extract the two-loop short-distant matching coefficients between quark quasi and lightcone PDFs in LaMET, and are valuable to improve the determination of the nucleon PDFs from first principles in future.

We compute the two-loop master integrals for leading-color QCD scattering amplitudes including a closed light-quark loop in tt¯H\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t}H $$\\end{document} production at hadron colliders. Exploiting numerical evaluations in modular arithmetic, we construct a basis of master integrals satisfying a system of differential equations in ϵ-factorized form. We present the analytic form of the differential equations in terms of a minimal set of differential one-forms. We explore properties of the function space of analytic solutions to the differential equations in terms of iterative integrals which can be exploited for studying the analytic form of related scattering amplitudes. Finally, we solve the differential equations using generalized series expansions to numerically evaluate the master integrals in physical phase space. As the first computation of a set of two-loop seven-scale master integrals, our results provide valuable input for analytic studies of scattering amplitudes in processes involving massive particles and a large number of kinematic scales.

A numerical routine for the crossed vertex diagram with a massive-particle loop

We present analytic results for the two-loop leading heavy top-quark contributions as required for precise predictions of electroweak observables. The Higgs boson mass is kept arbitrary. We discuss a set of recurrence relations for diagrams with three masses at zero momentum, which allow one to reduce the calculation to a few master integrals. Simple analytic expressions are obtained for the \ensuremath{\rho} parameter and for the Zbb\ifmmode\bar\else\textasciimacron\fi{} vertex. Results are pesented for the on-shell and the MS\ifmmode\bar\else\textasciimacron\fi{} definition of the top quark mass. We explicitly discuss and verify the validity of Ward-Takahashi identities and check that the use of an anticommuting ${\ensuremath{\gamma}}_{5}$ preserves the latter.

A bstract In this paper, we present analytical results for the two-loop QCD corrections to the production of two partons or a photon and a parton in hadronic collisions, mediated by loops of massive quarks. These amplitudes involve Feynman integrals defined on an elliptic curve. We compute them by generalizing our recent results for the production of two photons to include additional crossings of the corresponding master integrals, which we compute in terms of the same basis of independent iterated integrals. We discuss the analytical properties of the amplitudes, highlighting the cancellations of a large number of elliptic differential forms in their finite remainders. Finally, we elaborate on a strategy for their numerical evaluation based on generalized series expansions at singular points of the physical amplitude, through the introduction of suitable sets of variables that allow us to resolve all singularities.

The two loop crossed ladder vertex diagram with two massive exchanges

We present analytical formulas for the calculation of the two-center two-electron integrals in the basis of Slater geminals and products of Slater orbitals. Our derivation starts with establishing a inhomogeneous fourth-order ordinary differential equation that is obeyed by the master integral, the simplest integral with inverse powers of all interparticle distances. To solve this equation it was necessary to introduce a new family of special functions which are defined through their series expansions around regular singular points of the differential equation. To increase the power of the interparticle distances under the sign of the integral we developed a family of open-ended recursion relations. A handful of special cases of the integrals is also analysed with some remarks on simplifications that occur. Additionally, we present some numerical examples of the master integral that validate the usefulness and correctness of the key equations derived in this paper. In particular, we compare our results with the calculations based on the series expansion of the exp(-\gamma r12) term in the master integral.

Functional equations for one-loop master integrals for heavy-quark production and Bhabha scattering

Waves in wood: free vibrations of a wooden pole

We consider mixed strong-electroweak corrections to Higgs production via gluon fusion, in which the Higgs boson couples to the top quark. Using the method of differential equations, we compute all of the master integrals that contribute to this process at two loops through O ( ϵ 2 ) in the dimensional regularization parameter ϵ = ( d − 4 ) / 2 , keeping full analytic dependence on the top quark, Higgs, W , and Z boson masses. We present the results for these master integrals in terms of iterated integrals whose kernels depend on elliptic curves.

We studied the two-loop non-factorizable Feynman diagrams for the t-channel single-top production process in quantum chromodynamics. We present a systematic computation of master integrals of the two-loop Feynman diagrams with one internal massive propagator in which a complete uniform transcendental basis can be built. The master integrals are derived by means of canonical differential equations and uniform transcendental integrals. The results are expressed in the form of Goncharov polylogarithm functions, whose variables are the scalar products of external momenta, as well as the masses of the top quark and the W boson. We also gave a discussion on the diagrams with potential elliptic sectors.

In this talk we present the Simplified Differential Equations (SDE) Approach for Master Integrals (MI). Combined with the integrand reduction method for two-loop amplitudes it can pave the road for a fully automated NNLO calculation framework. Most recent achievements of the method, including double-box and pentabox MI calculations, are highlighted.

New parallel stochastic global integral and local differential equation modeling and inversion

Apresenta-se a aplicação dos operadores de fatorização para a resolução das principais equações diferenciais li­neares de segunda ordem da Física Matemática como alternativa para o método de Frobenius. Em equações mais simples, a fatoração reduz a equação diferencial de segunda ordem a um par de equações diferenciais de primeira ordem, cada qual forne­cendo uma das soluções linearmente independentes. Em outras, geralmente equações de auto-valores, os operadores de fatorização são identificados como operadores de levantamento e de abaixamento de índices, de modo que basta resolver a equação diferencial correspondente ao auto-valor de nível mais baixo, onde uma simples integração é suficiente. Verifica-se que a maioria das equações diferenciais comumente estudadas na Física Matemática podem ser fatoradas.