# Probes of the Standard Model effective field theory extended with a right-handed neutrino

## TL;DR

This paper extends the Standard Model effective field theory to include right-handed neutrinos, constrains their interactions using collider and decay data, and proposes new collider signatures involving top quarks.

## Contribution

It introduces constraints on dimension-six operators involving right-handed neutrinos and designs an LHC analysis for top quark decay signatures.

## Key findings

- Bounds above the TeV scale for most operators
- New collider signals involving top quark decays
- Analysis applicable to Majorana and long-lived neutrinos

## Abstract

If neutrinos are Dirac particles and, as suggested by the so far null LHC results, any new physics lies at energies well above the electroweak scale, the Standard Model effective field theory has to be extended with operators involving the right-handed neutrinos. In this paper, we study this effective field theory and set constraints on the different dimension-six interactions. To that aim, we use LHC searches for associated production of light (and tau) leptons with missing energy, monojet searches, as well as pion and tau decays. Our bounds are generally above the TeV for order one couplings. One particular exception is given by operators involving top quarks. These provide new signals in top decays not yet studied at colliders. Thus, we also design an LHC analysis to explore these signatures in the $t\overline{t}$ production. Our results are also valid if the right-handed neutrinos are Majorana and long-lived.