Improved bounds on the heavy neutrino productions at the LHC

Understand

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.