Looking for minimal inverse seesaw scenarios at the LHC with jet substructure techniques

Abstract

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 currently. Heavy RHNs may dominantly decay into ${W}^{\pm }{{\ell }}^{\mp }$ after being produced at the LHC. In this paper, we consider collider signatures of heavy pseudo-Dirac neutrinos in the context of the inverse seesaw scenario, with a sizable mixing with the SM neutrinos under two different flavor structures, viz. flavor diagonal and flavor non-diagonal (FND) scenarios. For the latter scenario we use a general parametrization for the model parameters by introducing an arbitrary orthogonal matrix and nonzero Dirac and Majorana phases. We then perform a parameter scan to identify allowed parameter regions which satisfy all experimental constraints. As an alternative channel to the traditional trilepton signature, we propose the opposite-sign di-lepton signature in the final state, in association with a fat jet from the hadronic decay of the boosted ${W}^{\pm }$. We specifically consider a fat jet topology and explore the required enhancements from exploiting the characteristics of the jet substructure techniques. We perform a comprehensive collider analysis to demonstrate the effectiveness of this channel in both of the scenarios, significantly enhancing the bounds on the RHN mass and mixing angles at the 13 TeV LHC. Interestingly the FND scenario can reach up to a 5-σ limit under the presence of the general parametrization at the high luminosity LHC.