Probing the Dirac or Majorana nature of the Heavy Neutrinos in pure leptonic decays at the LHC

TL;DR

This paper proposes a method to distinguish Dirac from Majorana heavy neutrinos at the LHC using leptonic decay asymmetries, supported by numerical analysis showing feasible detection for certain neutrino masses and mixings.

Contribution

It introduces a novel leptonic decay asymmetry technique to identify the nature of heavy neutrinos at the LHC, with numerical validation for experimental feasibility.

Findings

Distinguishable positron signatures for different heavy neutrino masses.

Feasibility of detection with 120 fb^{-1} at LHC RUN II.

Sensitivity to neutrino mixings above 10^{-6}.

Abstract

We propose a strategy for distinguishing the Dirac / Majorana character of heavy neutrinos with masses below the $W$ boson mass, using purely leptonic decays at the LHC. The strategy makes use of a forward-backward asymmetry of the opposite charge lepton in the $W^{+}\rightarrow l^{+}l^{+}l^{'-}\nu$ decay. In order to check the experimental feasibility of the model, we show, through a numerical analysis, that in the decay $W^{+}\rightarrow e^{+}e^{+}\mu^{-}\nu$ the two positrons in the final state can be distinguished for different ranges of the heavy neutrino masses. Finally, we estimated the number of events of $W^{+}\rightarrow e^{+}e^{+}\mu^{-}\nu$ for a Dirac and Majorana $N$ neutrino. For an integrated luminosity of 120 fb$^{-1}$ at LHC RUN II, signals can be found if heavy-to-light neutrino mixings are $ |U_{N \mu}|^2,|U_{N e}|^2 \gtrsim 10^{-6} $.