Probing the Dirac or Majorana nature of the heavy neutrinos in pure leptonic decays at the LHC

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+ -> l(+)l(+)l'(-)nu decay. In order to check the experimental feasibility of the model, we show-through a numerical analysis and for different ranges of the heavy neutrino masses-that in the decay W+ -> e(+)e(+)mu(-)nu one can distinguish the positron from the W decay from the positron coming from the heavy neutrino. Finally, we estimate the number of events at the LHC Run II for a Dirac and Majorana N neutrino with an integrated luminosity of 120 fb(-1). Signals can be found if heavy-to-light neutrino mixings are vertical bar U-N mu vertical bar(2); vertical bar U-Ne vertical bar(2) greater than or similar to 10(-6).