On the heavy Majorana neutrino and light sneutrino contribution to \bm{$e^{-}{e}^{-}\to {\ell }^{-}{\ell }^{-}$}, (\bm{$\ell =\mu ,\tau )$}

Abstract

The cross section for the reaction $e^{-}{e}^{-}\to {\ell }^{-}{\ell }^{-}$ ($\ell =\mu ,\tau$) is calculated in models with heavy Majorana neutrinos mediating lepton number violating amplitudes at the loop level. The contributing four-point functions are evaluated exactly (numerically) taking into account the full propagator dependence on external momenta, thereby extending %an earlier approximate low energy calculation to the energy range of interest for the next linear colliders an earlier approximate low energy calculation. The amplitude shows a non-decoupling behaviour relative to the heavy Majorana neutrino masses, but due to the stringent bounds on heavy-light mixing the signal cross section attains observable values only for the less constrained $\tau$ signal. The cross section induced by lepton number violation in the $SU(2{)}_L$ doublet sneutrino sector of supersymmetric extensions of the standard model is constrained by the upper limits on neutrino masses and probably too tiny to be observable.

Comments: Revtex 4, 5 figures