RGE effects on the LFV scale from meson decays

TL;DR

This paper investigates how lepton-flavor violating operators influence meson and lepton decays, deriving bounds on new physics scales and emphasizing the importance of QED corrections in operator evolution.

Contribution

It provides a comprehensive analysis of LFV effects on meson and lepton decays, including QED/QCD corrections and RGE evolution, to set bounds on LFV operator scales.

Findings

QED corrections significantly affect LFV operator bounds.

Derived new lower bounds on LFV scales from meson decay data.

Operator mixing enhances the sensitivity of LFV searches.

Abstract

We consider the lepton-flavor violating (LFV) lepton-quark dimension-6 operators and analyze their contributions to the LFV leptonic decays of vector, pseudoscalar, and scalar neutral mesons $M\to \ell_1 \ell_2$ as well as to $\mu(\tau) \rightarrow \ell ee, \ell \gamma\gamma$ decays. These operators contribute to the purely leptonic processes via quark loop. On the basis of quark-hadron duality, we relate these loops to the appropriate meson-exchange contributions. In this way, we extract lower bounds on the individual scales of the studied LFV operators from the experimental and phenomenological limits on the leptonic decays of mesons and leptons. As a byproduct, we shall obtain new limits on the LFV leptonic decays of flavored mesons from the experimental bounds on the three-body lepton decays. We study the effects of QED and QCD radiative corrections to the LFV lepton-quark operators in question. We derive for them the one-loop matrix of the RGE evolution and examine its effect on the previously derived tree-level limits on these operators. We show that the QED corrections are particularly relevant due to operator mixing. Specifically, for some of them the limits on their individual LFV scales improve by up to 3 orders of magnitude.