Radiative Decays of Charged Leptons in the Seesaw Effective Field Theory with One-loop Matching

TL;DR

This paper advances the understanding of charged lepton radiative decays by performing one-loop matching in the seesaw effective field theory, revealing new operators and providing precise decay rate calculations.

Contribution

It introduces the first one-loop matching calculation in SEFT, computing Wilson coefficients of six-dimensional operators affecting lepton decays.

Findings

New six-dimensional operators significantly impact decay rates.

Wilson coefficients are explicitly calculated for the first time.

Enhanced precision in predicting charged lepton radiative decay rates.

Abstract

The canonical type-I seesaw model with three heavy Majorana neutrinos is one of the most natural extensions of the standard model (SM) to accommodate tiny Majorana masses of three ordinary neutrinos. At low-energy scales, Majorana neutrino masses and unitarity violation of lepton flavor mixing have been extensively discussed in the literature, which are respectively generated by the unique dimension-five Weinberg operator and one dimension-six operator in the seesaw effective field theory (SEFT) with the tree-level matching. In this work, we clarify that a self-consistent calculation of radiative decays of charged leptons $\beta^- \to \alpha^- + \gamma$ requires the SEFT with one-loop matching, where new six-dimensional operators emerge and make important contributions. For the first time, the Wilson coefficients of all the relevant six-dimensional operators are computed by carrying out the one-loop matching between the effective theory and full seesaw model, and applied to calculate the total rates of radiative decays of charged leptons.