Type- 3/2 seesaw mechanism

Durmuş Demir,Ozan Sargın,Canan Karahan

doi:10.1103/physrevd.104.075038

Abstract

The type-I seesaw mechanism provides a natural explanation for tiny neutrino masses. The right-handed neutrino masses it requires are, however, too large to keep the Higgs boson mass at its measured value. We show that vector spinors, singlet leptons that are like right-handed neutrinos, generate tiny neutrino masses naturally through the exchange of spin-$1/2$ and spin-$3/2$ components. This one-step seesaw mechanism, which we call the type-$3/2$ seesaw, keeps the Higgs boson mass unchanged at one loop and gives cause therefore to no fine-tuning problem. If the on-shell vector spinor is a pure spin-$3/2$ particle, then it becomes a potential candidate for hidden dark matter which gets diluted due only to the expansion of the Universe. The type-$3/2$ seesaw provides a natural framework for the neutrino, Higgs boson, and dark matter sectors, with overall agreement with current experiments and observations.

Highlights

Neutrino oscillations [1,2] are proof that active neutrinos are massive
We show that vector spinors, singlet leptons that are like right-handed neutrinos, generate tiny neutrino masses naturally through the exchange of spin-1=2 and spin-3=2 components
This new mechanism, the type-3=2 seesaw, exhibits physically important features not found in the type-I seesaw

Summary

INTRODUCTION

Neutrino oscillations [1,2] are proof that active neutrinos are massive. Neutrino mass, whose nature is still an open question, is proof that there is new physics beyond the Standard Model (SM) [3,4,5,6,7,8]. The type-I seesaw mechanism, first and foremost [4], leads to small active neutrino masses [4] via the dimension-5 Weinberg operator [23] induced by the heavy right-handed neutrino mediation. We turn to the vector spinor and construct the type-3=2 seesaw, with a detailed discussion of its implications for leptogenesis, dark matter, and the Higgs boson mass. The right-handed neutrino N, a SM-singlet spin-1=2 neutral fermion [3,4], gives a simple model of the tiny neutrino masses. It couples to the active neutrinos νL through the left-handed lepton doublet L 1⁄4 ðνL; lLÞ as yN

Published by the American Physical Society

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CONCLUSION