Heavy neutrinos at future linear e+e? colliders

A bstract Neutrinos are among the most mysterious particles in nature. Their mass hierarchy and oscillations, as well their antiparticle properties, being intensively studied experiments around world. Moreover, many models of physics beyond Standard Model, baryon asymmetry or dark matter density Universe explained by introducing new species neutrinos. Among others, heavy neutrinos Dirac Majorana nature were proposed to solve open questions High Energy Physics. Such with masses above electroweak (EW) scale could be produced at future linear e + ? colliders, like Compact LInear Collider (CLIC) International Linear (ILC). We possibility observing decays qq? final state ILC running 500 GeV 1 TeV, CLIC 3 TeV. The analysis is based on W hizard event generation fast simulation detector response Delphes. from 200 3.2 TeV considered. estimated limits production cross sections, interpreted them terms neutrino-lepton coupling parameter $$ {V}_{\ell N}^2 V ? N 2 (effectively neutrino mixing angle) compared current coming LHC 13 expected hadron colliders. for lepton extending down values 10 7 6 , stricter than any other limit estimates published so far.