Searching for the Minimal Seesaw Models at the LHC and Beyond

Arindam Das

doi:10.1155/2018/9785318

Abstract

The existence of the tiny neutrino mass and the flavor mixing can be naturally explained by type I Seesaw model which is probably the simplest extension of the Standard Model (SM) using Majorana type SM gauge singlet heavy Right Handed Neutrinos (RHNs). If the RHNs are around the Electroweak- (EW-) scale having sizable mixings with the SM light neutrinos, they can be produced at the high energy colliders such as Large Hadron Collider (LHC) and future 100 TeV proton-proton (pp) collider through the characteristic signatures with the same-sign dilepton introducing lepton number violations (LNV). On the other hand Seesaw models, namely, inverse Seesaw, with small LNV parameter can accommodate EW-scale pseudo-Dirac neutrinos with sizable mixings with SM light neutrinos while satisfying the neutrino oscillation data. Due to the smallness of the LNV parameter of such models, the “smoking-gun” signature of same-sign dilepton is suppressed where the RHNs in the model will be manifested at the LHC and future 100 TeV pp collider dominantly through the Lepton number conserving (LNC) trilepton final state with Missing Transverse Energy (MET). Studying various production channels of such RHNs, we give an updated upper bound on the mixing parameters of the light-heavy neutrinos at the 13 TeV LHC and future 100 TeV pp collider.

Highlights

The experimental evidence of the neutrino oscillation and flavor mixings from neutrino oscillation experiments [1,2,3,4,5,6]indicates that the Standard Model (SM) is not enough to explain the existence of the tiny neutrino mass and flavor mixing
We study contributions coming from the gluon-gluon fusion, photon-proton interactions, and Vector Boson Fusion (VBF) processes to produce the Right Handed Neutrinos (RHNs) at the Large Hadron Collider (LHC) and beyond
In this paper we have studied both type I and inverse Seesaw models where SM singlet RHNs are involved

Summary

Introduction

The experimental evidence of the neutrino oscillation and flavor mixings from neutrino oscillation experiments [1,2,3,4,5,6]. In case of Seesaw mechanism the Dirac Yukawa matrix (YD) can carry the flavors where the RHN mass matrix is considered to be diagonal This case is favored by the neutrino oscillation data as studied in [16, 30, 38,39,40,41,42]. Since any number of singlets can be added in a gauge theory without contributing to anomalies, one can utilize such freedom to find a natural alternative of the lowscale realization of the Seesaw mechanism Simplest among such scenarios is commonly known as the inverse Seesaw mechanism [43, 44] where a small Majorana neutrino mass originates from tiny LNV parameters rather than being suppressed by the RHN mass as done in the case of conventional Seesaw mechanism.

Production Cross Sections

Decay of the RHNs at the LHC

Bounds on the Mixing Angle

Conclusions