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Physik-Institut Group of Thomas Gehrmann

ERC Advanced Grant TOPUP

Theory of Particle Collider Processes at Ultimate Precision (TOPUP)

The Large Hadron Collider (LHC) at CERN probes the interaction of elementary particles at unprecedented energy and to very high precision. The full exploitation of the upcoming data from the LHC relies on a close interplay between theory and experiment, which calls in particular for highly accurate theoretical predictions. This theoretical accuracy can be achieved only though the expansion of the fundamental scattering amplitudes to sufficiently high order in perturbation theory.

This project aims to meet this challenge for modern collider physics by providing the conceptual and technical foundations for theory predictions at ultimate precision. TOPUP will develop and establish a new standard of theoretical precision in the description of physical observables at the LHC based on perturbation theory expanded to the third non-trivial order (N3LO). We will achieve this ambitious goal by targeting the main obstacles in present-day methods, and by developing novel ways for the computation of multi-loop scattering amplitudes and in the understanding and handling of unresolved multi-particle emission.

The concrete goal of the project is to enable theoretical predictions at ultimate precision for multiple processes in high-energy particle collisions with full final state kinematical information. This will lead to a more precise extraction of fundamental physics parameters, such as couplings and particle masses. The newly developed methods will be applied to the derivation of the process-independent four-loop corrections to the Altarelli-Parisi splitting functions, the three-loop matrix elements for a number of fundamental scattering processes and fully differential N3LO predictions for several process-specific key observables. These calculations will shape and challenge the newly developed methods in cutting-edge applications and provide crucial input to the theoretical interpretation of the LHC precision physics program.

The project started in fall 2021.