Series expansions methods for Feynman integrals, the DiffExp Mathematica package, and various applications

I will discuss the computation of Feynman integrals from their systems of differential equations in terms of series solutions along one-dimensional contours in phase-space. In arXiv:1907.13156 and arXiv:1911.06308, we showed that this method can be used for the high-precision numerical evaluation of non-planar master integrals relevant for Higgs + jet production at NLO with full heavy quark mass dependence. More recently, I developed in arXiv:2006.05510 the Mathematica package DiffExp that provides a public implementation of such series expansion methods, and which can be applied to user-provided systems of differential equations. I will discuss the algorithms underlying the DiffExp package, and a number of possible applications of the package, such as the computation of the (earlier mentioned) H+j integral families, and the computation of Feynman integrals for which the underlying space of functions is not well studied.

Wednesday 16th December 2020, ore 14:30 — Webex seminar

Master integrals contributing to two loop planar ttgg amplitudes including massive fermion loops

In this talk I am going to discuss the analytic form for two loop amplitudes for ttgg. In particular, I will discuss in detail the master integrals with an internal massive loop, and the special functions they evaluate to. The presence of elliptic curves in these master integrals make the computations particularly interesting. I will also shed some light on how to compute these master integrals numerically.

Wednesday 2nd December 2020, ore 14:30 — Zoom seminar

Status of theory predictions for exclusive b->sll decays

I will discuss theory predictions for exclusive b->s ll decays within the SM and beyond, with emphasis on the hadronic matrix elements. There are two categories of these matrix elements: local form factors, and nonlocal contributions arising from e.g. four-quark operators. I will report the status and report recent progress from QCD-based methods on both types of hadronic matrix elements. A particular focus will be a recent derivation of a dispersive bound on the nonlocal contributions as discussed in arXiv:2011.09813.

Wednesday 9th December 2020, ore 14:30 — Webex seminar

Electroweak corrections to Higgs production in gluon fusion

The discovery of the Higgs boson at the LHC is one of the milestones in the establishment of fruitful synergies between high precision theoretical prediction and experimental measurement. It started an on-going program that aims for the prediction and measurement of its properties at record precision and hopefully yields direct or indirect evidence for new physics beyond the Standard Model. One key ingredient for accessing the properties of the Higgs is the theoretical prediction of its total cross-section in the dominant production channel gluon-fusion which is known with a theoretical uncertainty of only 5%. Half of this uncertainty is purely due to unknown mass effects and understanding them will double the accuracy of our theoretical prediction.

The NLO effects of weak gauge-bosons in the gluon-fusion Higgs production cross-section were estimated by an unphysical infinite boson-mass approximation which results in a 1% uncertainty due to the unknown aforementioned mass effects. The reduction of this uncertainty involves the computation of massive 2-loop 4-point integrals, which are notoriously difficult to compute in a traditional framework of loop-integrals.

Wednesday 25th November 2020, ore 14:30 — Zoom seminar