Majorana Neutrinos and Clockworked Yukawa Couplings contribution to non-observation of the rare leptonic decay $ l_{i}\rightarrow l_{j} \gamma $, Clockwork Photon and Clockwork Graviton

TL;DR

This paper investigates how the clockwork mechanism, involving heavy fermions and Majorana masses, can explain the non-observation of rare leptonic decays and explores its implications for neutrino masses and new particles.

Contribution

It introduces a comprehensive analysis of clockwork models with Majorana masses, deriving particle masses and Yukawa couplings, and discusses their impact on charged lepton flavor violation constraints.

Findings

Neutrino masses are generated via heavy clockwork particles and seesaw mechanisms.

Constraints from non-observation of $ \, \mu \rightarrow e \gamma \, $ limit the clockwork fermion mass scale.

The clockwork mechanism can be applied to fermions, gauge bosons, and gravitons in both discrete and continuum forms.

Abstract

The clockwork is an extra-dimensional set-up for generating light particles with exponentially suppressed or hierarchical couplings of light particles with N massive states having comparable masses near the threshold scale of the mechanism in theories which contain no small parameters at the fundamental level. We explore the prospect of charged lepton flavour violation (cLFV) in a clockwork framework which encompasses Dirac mass terms as well as Majorana mass terms for the new clockwork fermions. We deive the masses of the non zero clockwork Majorana masses, and new particles in a clockwork framework and for their Yukawa couplings to the lepton doublets, in the framework where the clockwork parameters are universal. When the new clockwork Majorana masses are non zero, neutrino masses are generated as a result from the exchange of heavy messenger particles such as right handed iso$-$singlet neutrinos or iso$ - $triplet scalar bosons known as the seesaw mechanism. In the case of non zero clockwork Majorana masses, owing to the sizable effective Yukawa couplings of the higher mass modes neutrino masses can only be made tiny by conjecturing large Majorana mass in the teraelectron volt range for allthe clockwork gears. This is apparent from the constraints on the mass scale of the clockwork fermions due to the non-observation of the rare cLFV decay $ \mu\rightarrow e\gamma $, $ \tau \rightarrow \mu \gamma $, $ \tau\rightarrow e\gamma $. A general description of the clockwork mechanism valid for fermions, gauge bosons, and gravitons is discussed here. This mechanism can be implemented with a discrete set of new fields or, in its continuum version, through an extra spatial dimension.