Displaced fat-jets and tracks to probe boosted right-handed neutrinos in the U(1) model

We investigate the pair-production of Right-Handed Neutrinos (RHNs) via a B- LZ boson and present the sensitivity studies of the active-sterile neutrino mixing (| V|) at the High-Luminosity run of the LHC (HL-LHC) and a future pp collider (FCC-hh). We focus on RHN states with a mass of 10 - 70 GeV which naturally results in displaced vertices for small | V|. Being produced through a mass resonance with MZ′≥1 TeV, the RHNs are heavily boosted, leading to collimated decay products that give rise to fat-jets. We investigate the detection prospect of dedicated signatures in the inner detector and the muon spectrometer, namely a pair of displaced fat-jets and the associated tracks, respectively. We find that both the HL-LHC and FCC-hh can be sensitive to | V| > 10 and | V| > 10 with the number of events reaching O(10) and O(10 ) , respectively. This allows probing the generation of light neutrino masses through the Seesaw mechanism.