Two-body lepton-flavour-violating decays in a 2HDM with soft family-lepton-number breaking

Abstract

We evaluate the decays $$ {\ell}_1^{\pm } $$ ℓ 1 ± → $$ {\ell}_2^{\pm}\gamma $$ ℓ 2 ± γ , Z → $$ {\ell}_1^{+}{\ell}_2^{-} $$ ℓ 1 + ℓ 2 − , and h → $$ {\ell}_1^{+}{\ell}_2^{-} $$ ℓ 1 + ℓ 2 − , where ℓ1 and ℓ2 are charged leptons with different flavours and h is the scalar particle with mass 125.25 GeV, in a two-Higgs-doublet model where all the Yukawa-coupling matrices conserve the lepton flavours but the Majorana mass terms of the right-handed neutrinos break the flavour lepton numbers. We find that (1) the decays $$ {\ell}_1^{\pm } $$ ℓ 1 ± → $$ {\ell}_2^{\pm}\gamma $$ ℓ 2 ± γ require large Yukawa couplings and very light right-handed neutrinos in order to be visible, (2) the decays Z → $$ {\ell}_1^{+}{\ell}_2^{-} $$ ℓ 1 + ℓ 2 − will be invisible in all the planned experiments, except in a very restricted range of circumstances, but (3) the decays h → $$ {\ell}_1^{+}{\ell}_2^{-} $$ ℓ 1 + ℓ 2 − may be detected in future experiments for rather relaxed sets of input parameters.

Charged lepton flavor violating processes in the Grimus-Neufeld model

“…While virtually all scenarios can fit the current experimental constraints, it is far harder to claim the strictly excluded regions unambiguously, especially when one studies more general scenarios with an overwhelming number of free parameters (see e.g. [28]). A look at less general models, with more exposed and isolated effects on the cLFV from the neutrino sector, naturally provides a solution to this problem.…”

Charged lepton flavor violating processes in the Grimus-Neufeld model

“…While virtually all scenarios can fit the current experimental constraints, it is far harder to claim the strictly excluded regions unambiguously, especially when one studies more general scenarios with an overwhelming number of free parameters (see e.g. [22]). A look at less general models, with more exposed and isolated effects on the cLFV from the neutrino sector, naturally provides a solution to this problem.…”