Constraints on 2l2q operators from $\mu - e$ flavour-changing meson decays

TL;DR

This paper analyzes constraints on 2l2q operators from meson decays involving muon-electron flavor change, providing analytic decay formulas and examining how renormalization group effects influence these constraints.

Contribution

It offers a comprehensive EFT framework with analytic decay rate formulas and explores the impact of RG mixing on operator constraints at different energy scales.

Findings

RG mixing weakens scalar and pseudoscalar operator constraints

Analytic formulas for meson decay rates in EFT

Constraints translated from experimental to weak scale

Abstract

We study lepton flavour violating two- and three-body decays of pseudoscalar mesons in Effective Field Theory (EFT). We give analytic formulae for the decay rates in the presence of a complete basis of QED and QCD-invariant operators. The constraints are obtained at the experimental scale, then translated to the weak scale via one-loop RGEs. The large RG-mixing between tensor and (pseudo)scalar operators weakens the constraints on scalar and pseudoscalar operators at the weak scale.