# Full Angle Dependence of the Four-Loop Cusp Anomalous Dimension in QED

#### Full Angle Dependence of the Four-Loop Cusp Anomalous Dimension in QED

- Event time: 5:00pm
- Event date: 24th March 2021
- Speaker: Dr Kai Yan (MPI Munich)
- Location: Online - details to follow

### Event details

Angle-dependent cusp anomalous dimension governs the divergences coming from soft gluon exchanges between massive particles. We compute matter-dependent quartic Casimir component, the first truly non-planar contribution. Our result sheds new light on the infrared structure of gauge-theory amplitudes at generic cusp angle. On the one hand, it interpolates between various physically interesting kinematic limits in both maximally supersymmetric gauge theory (N=4 sYM), and QCD. On the other hand, it constitutes the first quantum correction beyond propagator-type diagrams in the abelian theory. Obtaining an analytic four-loop prediction, with exact kinematic dependence, is beyond the state of the art of most approaches. To overcome various technical difficulties, we developed an algorithm for solving system of differential equations, based only on partial knowledge of the canonical basis. We demonstrate its applicability and usefulness to a large-scale problem, and in particular, systems of quasi-finite integrals.

Meeting link:

https://ed-ac-uk.zoom.us/j/81331461714?pwd=YjZnZjRuR0dTRWViSUZlcTBNOGx6UT09

Meeting ID: 813 3146 1714

Passcode: iS5Nx9P2

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https://ed-ac-uk.zoom.us/skype/81331461714

#### Event resources

### About Particle Physics Theory seminars

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..