Heavy neutrino search via semileptonic higgs decay at the LHC

Teruki Kamon,Yu Gao,Arindam Das

doi:10.1140/epjc/s10052-019-6937-7

Abstract

In the inverse see-saw model the effective neutrino Yukawa couplings can be sizable due to a large mixing angle between the light (nu )and heavy neutrinos (N). When the right handed neutrino (N) can be lighter than the Standard Model (SM) Higgs boson (h). It can be produced via the on-shell decay of the Higgs, hrightarrow Nnu at a significant branching fraction at the LHC. In such a process N mass can be reconstructed in its dominant Nrightarrow W ell decays. We perform an analysis on this channel and its relevant backgrounds, among which the W+jets background is the largest. Considering the existing mixing constraints from the Higgs and electroweak precision data, the best sensitivity of the heavy neutrino search is achieved for benchmark N mass at 100 and 110 GeV for upcoming high luminosity LHC runs.

Highlights

In high energy collider experimental point of view, it is interesting if the heavy neutrino mass lies at the TeV scale or smaller, because such heavy neutrinos could be produced at high energy colliders, such as the Large Hadron Collider (LHC) and the Linear Collider (LC) being projected as energy frontier physics in the future
Since the heavy neutrinos are singlet under the Standard Model (SM) gauge group, they obtain the couplings with the weak gauge bosons only through the mixing via the Dirac Yukawa coupling
For the seesaw mechanism at the TeV scale or smaller, the Dirac Yukawa coupling is too small (YD ∼ 10−6 − 10−5) to produce the observable amount of the heavy neutrinos at the colliders. There is another type of seesaw mechanism so-called the inverse seesaw [15,16], where the small neutrino mass is obtained by tiny lepton-number-violating parameters, rather than the suppression by the heavy neutrino mass scale in the ordinary seesaw mechanism

Summary

Introduction

In high energy collider experimental point of view, it is interesting if the heavy neutrino mass lies at the TeV scale or smaller, because such heavy neutrinos could be produced at high energy colliders, such as the Large Hadron Collider (LHC) and the Linear Collider (LC) being projected as energy frontier physics in the future. For the seesaw mechanism at the TeV scale or smaller, the Dirac Yukawa coupling is too small (YD ∼ 10−6 − 10−5) to produce the observable amount of the heavy neutrinos at the colliders. In the collider analysis we consider a minimal set up where both of MN are proportional to the 2 × 2 unit matrix (12×2) where the entire flavor mixing structure lies in μ which is another 2 × 2 matrix keeping YD as a diagonal matrix proportional to 12×2 Such a scenario can reproduce the neutrino oscillation data. It means that there are two degenerate generations of each of NR and S whose mass can be considered at the TeV scale.

Bounds on the mixings

Collider signals and backgrounds

Conclusion