Testing tree level TeV scale seesaw scenarios in $\mu$TRISTAN

Abstract

We investigate TeV scale seesaw scenarios at ${\mu }^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{+}$ colliders in the $\mu$TRISTAN experiment. In minimal type-I seesaw scenario we consider two generations of Standard Model (SM) singlet heavy Majorana type Right Handed Neutrinos (RHNs) which couples with SM gauge bosons through light-heavy neutrino mixing. We discuss the prospects of probing heavy neutrinos via the processes such as ${\mu }^{+}{e}^{-}\to \nu N_i\to e^{+}jj\nu$ or ${\mu }^{-}jj\nu$ for $\sqrt{s}=346$~GeV and $1{\text{ ab}}^{-1}$ luminosity. Studying these process, we estimate limits on the light-heavy neutrino mixing angles as a function of heavy neutrino mass, which could be two orders of magnitude stronger than electroweak precision data. Further, we study the effect of doubly charged scalar boson $(H^{++})$ from the type-II seesaw scenario in ${\mu }^{+}{\mu }^{+}$ collision at $\sqrt{s}=2$ TeV. In this case we consider ${\mu }^{+}{\mu }^{+}\to {\ell }_i^{+}{\ell }_j^{+}$ and ${\mu }^{+}{\mu }^{+}\to H^{++}Z/\gamma$ processes followed by the same sign dilepton decay of $H^{++}$. We find that events involving $e^{+}{e}^{+}$ among these final states can probe the neutrino mass ordering in $\mu$TRISTAN experiment at 5$\sigma$ significance. In addition to that we study the production of positively charged triplet fermion in $\mu$TRISTAN following ${\mu }^{+}{\mu }^{+}\to {\mu }^{+}{\Sigma }^{+}$ process where ${\Sigma }^{+}$ decays into ${\mu }^{+}jj$ mode through $Z$ boson exchange. Considering a triplet at 1 TeV and studying SM backgrounds we estimate the discovery potential of ${\mu }^{+}{\mu }^{+}jj$ signal at $\mu$TRISTAN with respect to projected luminosity.

Comments: 23 pages, 16 figures, elaborated and matched published version in PRD