A Study of the Charged Scalar in the Zee Model

TL;DR

This paper investigates the charged scalar in the Zee model with a light right-handed neutrino, updating constraints on couplings and predicting bounds on lepton universality violations in W and Z decays.

Contribution

It introduces an extension of the Zee model with a light right-handed neutrino and updates experimental constraints on related couplings.

Findings

Muon decay constraints limit scalar couplings.

Predicted upper bounds on lepton universality violation.

Constraints inform rare Z decay predictions.

Abstract

An extension of the Zee model involving a light right handed neutrino, nu_R is considered. We update constraints on couplings between the bilepton scalar, the active neutrinos, nu_R and the charged leptons. We find that the most stringent constraint currently comes from measurements limiting the width of the decay mu -> e gamma. These are used to predict the upper bound on violation of lepton universality in leptonic W boson decays and rare Z decays, such as Z -> e mu.