Challenging Sterile Neutrino Searches at the LHC Complemented by Jet Substructure Techniques

Simple extensions of the Standard Model (SM) with additional Right Handed Neutrinos (RHNs) can elegantly explain the existence of small neutrino masses and their flavor mixings. Collider searches for sterile neutrinos are being actively pursued at the Large Hadron Collider (LHC) currently. Heavy RHNs may dominantly decay into $W^\pm \ell^\mp$ after being produced at the LHC. In this paper, we consider the challenging, opposite-sign di-lepton signature in the final state, in association with hadronic decay of the $W^\pm$. For the latter, we will specifically consider a fat jet topology and explore enhancements from jet substructure techniques. Though collimated and large radius topologies and jets have been considered earlier in this context, applications of jet substructure methods have hitherto been largely unexplored. Amongst the simple SM extensions with sterile right-handed neutrinos, we consider seesaw and inverse seesaw models, to sharpen our discussions and limits. SM neutrino masses in the former case are generated by a large lepton number violating parameter whereas in the later a small lepton number violating parameter is responsible for the same; requiring the RHNs to be Majorana and pseudo-Dirac type respectively. Exploiting the fat jet and jet substructure techniques, we demonstrate the effectiveness of this alternative channel and show that the bounds on the RHN mass and mixing angles at the 13 TeV LHC may be enhanced significantly.