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T: Fachverband Teilchenphysik

T 110: Other Theory

T 110.1: Vortrag

Donnerstag, 23. März 2023, 15:50–16:05, HSZ/0201

The use of Fierz identities beyond one loop — •Sophie Kollatzsch^1,2, Adrian Signer^1,2, Dominik Stöckinger³, and Yannick Ulrich⁴ — ¹Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — ²Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland — ³Institut für Kern- und Teilchenphysik, TU Dresden, DE-01069 Dresden, Germany — ⁴Institute for Particle Physics Phenomenology, University of Durham, South Road, Durham DH1 3LE, United Kingdom

EFTs typically contain dimension-six four-fermion operators. Different basis choices of such operators are possible by applying Fierz identities to rearrange four-fermion expressions. In d dimensions, such Fierz identities are not strictly valid; hence the question arises how such a basis change has to be treated at the (multi-)loop level. We discuss the treatment of so-called Fierz-evanescent operators, resulting in (finite) shifts of Wilson coefficients. Motivated by an abelian toy model, we show how the two-loop QED effects of specific Fierz-evanescent operators are absorbed into the renormalisation. As an example, we demonstrate how those basis changes affect the calculation of µ → e γ at next-to-leading order.