Improved bounds on the heavy neutrino productions at the LHC

TL;DR

This paper derives improved bounds on heavy neutrino production at the LHC by analyzing various initial states and recent experimental data, enhancing the constraints on neutrino mixing angles and projecting future search sensitivities.

Contribution

It provides new upper bounds on light-heavy neutrino mixing angles by considering multiple production channels and recent collider data, and extends the analysis to future LHC runs at 14 TeV.

Findings

Improved upper bounds on neutrino mixing angles using 8 TeV LHC data.

Analysis of multiple initial states enhances the bounds compared to previous studies.

Projected sensitivities for 14 TeV LHC with high luminosity are provided.

Abstract

The Majorana neutrino in type-I seesaw and the pseudo-Dirac neutrinos in the inverse seesaw can have sizable mixings with the light neutrinos in the standard model (SM), through which the heavy neutrinos can be produced at the Large Hadron Collider (LHC). In producing the heavy neutrinos we study a variety of initial states such as quark-quark, quark-gluon and gluon-gluon as well as photon mediated processes. For the Majorana heavy neutrino production we consider same-sign di-lepton plus di-jet as the signal events. Using the recent ATLAS and CMS data at $\sqrt{s}=$ 8 TeV with 20.3 fb$^{-1}$ and 19.7 fb$^{-1}$ luminosities, respectively, we obtain direct upper bounds on the light-heavy neutrino mixing angles. For the pseudo-Dirac heavy neutrino production we consider the final sate with tri-lepton plus missing energy as the signal events. Using the recent anomalous multi-lepton search by CMS at $\sqrt{s}=$ 8 TeV with 19.5 fb$^{-1}$ luminosity we obtain upper bounds on the mixing angles. Taking the varieties of initial states into account, the previously obtained upper bounds on the mixing angles have been improved. We scale our results at the 8 TeV LHC to obtain a prospective search reach at the 14 TeV LHC with high luminosities.