Box enhanced Charged Lepton Flavor Violation in the Grimus-Neufeld model

TL;DR

This paper updates bounds on charged lepton flavor violation in the Grimus-Neufeld model by exploring extended parameter space, highlighting the significance of three-body decays and the impact of Majorana phases on constraints.

Contribution

It extends previous analyses by including nonzero Majorana phases and heavier charged Higgs masses, revealing new dominant decay channels and parameter space restrictions.

Findings

Three-body cLFV decays become significant at higher charged Higgs masses.

Majorana phases can alter bounds on model parameters by up to an order of magnitude.

Two-body decays dominate at smaller masses, constraining the parameter space tightly.

Abstract

In the Grimus-Neufeld model (GNM) the neutrino mass generation from an extended Higgs sector leads to bounds from Charged Lepton Flavour Violating (cLFV) processes. Here we update bounds from the previous study by extending the parameter space to nonvanishing Majorana phase of the Pontecorvo-Maki-Nakagawa-Sakata matrix and to heavier charged Higgs boson masses. Three-body cLFV decays are shown to contribute significantly in large mass regions, as the boxes are enhanced relatively to photonic diagrams. This is in contrast to the smaller mass region studied before, in which the two-body decays tightly restrict the parameter space. The Majorana phase is shown to change limits within one order of magnitude. The tiny seesaw scale is assumed, which makes the cLFV decays of the GNM to be similar to the scotogenic model and the scoto-seesaw models.