## Biography

Ruth Britto is a theoretical physicist studying fundamental interactions. She is best known for her work on scattering amplitudes, which are mathematical functions characterizing the production of elementary particles, for example in high-energy collider experiments designed for discovering and analyzing new particles and new physical behaviours. She is currently probing deep mathematical structure in these functions, with the aim of offering powerful computational algorithms and revealing unknown principles of quantum field theory.

Born in Binghamton, New York, she earned degrees in mathematics from MIT and in physics from Harvard, and held research positions at the Institute for Advanced Study, the University of Amsterdam, Fermi National Accelerator Laboratory, and the Commissariat à l'énérgie atomique before coming to Trinity College Dublin in 2014, where she is an Associate Professor in Theoretical Physics.

## Publications and Further Research Outputs

### Peer-Reviewed Publications

**Samuel Abreu, Ruth Britto, Claude Duhr, Einan Gardi, James Matthew, Coaction for Feynman integrals and diagrams, Proceedings of Science, Loops and Legs in Quantum Field Theory, St. Goar, 2018**

**Samuel Abreu, Ruth Britto, Claude Duhr, Einan Gardi, Algebraic structure of cut Feynman integrals and the diagrammatic coaction, Physical Review Letters, 119, (5), 2017, p051601-**

**Samuel Abreu, Ruth Britto, Claude Duhr, Einan Gardi, Diagrammatic Hopf algebra of cut Feynman integrals: the one-loop case, Journal of High Energy Physics, 1712, 2017, p090-**

**Samuel Abreu, Ruth Britto, Claude Duhr, Einan Gardi, Cuts from residues: the one-loop case, Journal of High Energy Physics, (1706), 2017, p114-**

**Samuel Abreu, Ruth Britto, Claude Duhr, Einan Gardi, The diagrammatic coaction and the algebraic structure of cut Feynman integrals , Proceedings of Science, RADCOR 2017, St. Gilgen, 2017**

**S. Abreu, R. Britto, H. Grönqvist, Cuts and coproducts of massive triangle diagrams, Journal of High Energy Physics, 1507, 2015, p111-**

**S. Abreu, R. Britto, C. Duhr, E. Gardi, From multiple unitarity cuts to the coproduct of Feynman integrals, Journal of High Energy Physics, 2014, (10), 2014, p125-**

## Research Expertise

### Description

Scattering amplitudes play a key role in high-energy physics. Not only do they describe the actual scattering taking place in collider experiments--of current importance in the era of the Large Hadron Collider (LHC)--but they also illuminate the formal aspects of quantum field theories, such as divergent behavior or integrability. Amplitudes are thus useful both practically and formally, but their availability is limited by the difficulty of computing them. As the number of particles in the scattering process increases, or the perturbative expansion is carried out to higher order, the traditional technique of Feynman rules fails to be feasibly implementable. This difficulty has prompted the innovation of new techniques. Notable among these are on-shell techniques, in which the basic building blocks are complete amplitudes, rather than fundamental interactions. The on-shell framework has surpassed traditional Feynman diagram expansions, both in delivering new results and in expressing them in formulas that are not only compact, but also deeply illuminating. My research develops the on-shell framework to incorporate all theories and configurations of physical interest, building upon recent developments in pure mathematics.### Projects

**Title****Loop Amplitudes in Quantum Field Theory**

**Summary**- The traditional formulation of relativistic quantum theory is ill-equipped to handle the range of difficult computations needed to describe particle collisions at the Large Hadron Collider (LHC) within a suitable time frame. Yet, recent work shows that probability amplitudes in quantum gauge field theories, such as those describing the Standard Model and its extensions, take surprisingly simple forms. The simplicity indicates deep structure in gauge theory that has already led to dramatic computational improvements, but remains to be fully understood. For precision calculations and investigations of the deep structure of gauge theory, a comprehensive method for computing multi-loop amplitudes systematically and efficiently must be found. The goal of this proposal is to construct a new and complete approach to computing amplitudes from a detailed understanding of their singularities, based on prior successes of so-called on-shell methods combined with the latest developments in the mathematics of Feynman integrals. Scattering processes relevant to the LHC and to formal investigations of quantum field theory will be computed within the new framework.

**Funding Agency**- European Research Council

**Date From**- 2015-10-01

**Date To**- 2020-09-30