engleski

TeV-scale Seesaw with Quintuplet Fermions

We propose a new seesaw model based on fermionic hypercharge zero weak quintuplet in conjunction with additional scalar quadruplet which attains an induced vev. The model provides both tree-level seesaw ~ v^6/M^5 and a loop-suppressed radiative ~ (1 / 16 \pi^2) v^2/M contributions to active neutrino masses. The empirical masses m_\nu ~ 10^{; ; -1}; ; eV can be achieved with M ~ TeV new states, accessible at the LHC. For 5 fb^{; ; -1}; ; of accumulated integrated luminosity at the LHC, there could be ~ 500 doubly-charged \Sigma^{; ; ++}; ; or \bar{; ; \Sigma^{; ; ++}; ; }; ; fermions with mass M_\Sigma = 400 GeV, leading to interesting multi-lepton signatures. The neutral component of the fermion quintuplet, previously identified as minimal dark matter candidate, becomes unstable in the proposed seesaw setup. The stability can be restored by introducing a Z_2 symmetry, in which case neutrinos get mass only from radiative contributions.

Neutrino mass; Exotic leptons; Dark matter

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