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

Abstract

Abstract We evaluate the decays ℓ 1 ± $$ {\ell}_1^{\pm } $$ → ℓ 2 ± γ $$ {\ell}_2^{\pm}\gamma $$ , Z → ℓ 1 + ℓ 2 − $$ {\ell}_1^{+}{\ell}_2^{-} $$ , and h → ℓ 1 + ℓ 2 − $$ {\ell}_1^{+}{\ell}_2^{-} $$ , where ℓ 1 and ℓ 2 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 ℓ 1 ± $$ {\ell}_1^{\pm } $$ → ℓ 2 ± γ $$ {\ell}_2^{\pm}\gamma $$ require large Yukawa couplings and very light right-handed neutrinos in order to be visible, (2) the decays Z → ℓ 1 + ℓ 2 − $$ {\ell}_1^{+}{\ell}_2^{-} $$ will be invisible in all the planned experiments, except in a very restricted range of circumstances, but (3) the decays h → ℓ 1 + ℓ 2 − $$ {\ell}_1^{+}{\ell}_2^{-} $$ may be detected in future experiments for rather relaxed sets of input parameters.

Keywords

• Phenomenological Models