Testing left-right symmetry with an inverse seesaw mechanism at the LHC

Abstract

In the left-right symmetric models, a heavy charged gauge boson ${W}^{\ensuremath{'}}$ can decay to a lepton and a right-handed neutrino (RHN). If the neutrino masses are generated through the standard type-I seesaw mechanism, the Yukawa couplings controlling two-body decays of the RHN become very small. As a result, the RHN decays to another lepton and a pair of jets via an off-shell ${W}^{\ensuremath{'}}$. This is the basis of the Keung-Senjanovi\ifmmode \acute{c}\else \'{c}\fi{} (KS) process, which was originally proposed as a probe of lepton number violation at the LHC. However, if a different mechanism like the inverse seesaw generates the neutrino masses, a TeV-scale RHN can have large Yukawa couplings and hence dominantly decay to a lepton and a $W$ boson, leading to a kinematically different process from the KS one. We investigate the prospect of this unexplored process as a probe of the inverse seesaw mechanism in the left-right symmetric models at the High Luminosity LHC (HL-LHC). Our signal arises from the Drell-Yan production of a ${W}^{\ensuremath{'}}$ and leads to two high-${p}_{T}$ same-flavour-opposite-sign leptons and a boosted $W$-like fatjet in the final state. We find that a sequential ${W}^{\ensuremath{'}}$ with mass up to $\ensuremath{\sim}6\text{ }\text{ }\mathrm{TeV}$ along with a TeV-scale RHN can be discovered at the HL-LHC.