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

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.