# Vendredi 7 mai 2021

14h00 – 15h00,

### Power counting in Lepton Flavour Violation

#### Marco Ardu

Motivated by the observation of neutrino masses, Lepton Flavour Violation is new physics expected to occur. Assuming an energy scale for new physics beyond the reach of LHC, the Standard Model Effective Field Theory is a natural model-independent framework to describe it, and experimental searches of Lepton Flavor Violation can probe the size of the Wilson coefficients, which evolve with the energy scale.
I will discuss the introduction of a small power-counting parameter aimed at organizing the various perturbative expansions that appear in the Renormalization Group Equations of the Standard Model Effective Field Theory. This allows us to identify the leading order" and, in a bottom-up perspective, generally assess to which contributions Lepton Flavour Violating observables could be sensitive. With the upcoming improvement of experimental sensitivities, we find that in the mu->e sector there is potential sensitivity to some dimension eight operators and to selected two-loop anomalous dimensions effects that are currently unavailable in the literature. The power counting scheme is also employed to discuss some approximation that will simplify the one-loop running.

mai 2021 :