Abstract
We examine the observability of heavy neutrino (νh) signatures of a U(1)′ enlarged Standard Model (SM) encompassing three heavy Majorana neutrinos alongside the known light neutrino states at the the Large Hadron Collider (LHC). We show that heavy neutrinos can be rather long-lived particles producing distinctive displaced vertices that can be accessed in the CERN LHC detectors. We concentrate here on the gluon fusion production mechanism gg → H1,2 → νhνh, where H1 is the discovered SM-like Higgs and H2 is a heavier state, yielding displaced leptons following νh decays into weak gauge bosons. Using data collected by the end of the LHC Run 2, these signatures would prove to be accessible with negligibly small background.
Highlights
The special case in which the conserved charge of the extra Abelian symmetry is the B − L number, with B and L the baryon and lepton charges, respectively, is attractive from a phenomenological point of view
We examine the observability of heavy neutrino signatures of a U(1)′ enlarged Standard Model (SM) encompassing three heavy Majorana neutrinos alongside the known light neutrino states at the the Large Hadron Collider (LHC)
We show that heavy neutrinos can be rather long-lived particles producing distinctive displaced vertices that can be accessed in the CERN LHC detectors
Summary
We study a minimal renormalizable Abelian extension of the SM with only the matter content necessary to satisfy the cancellation of the gauge and the gravitational anomalies. The existence of a scalar field generating the Majorana mass for RH neutrinos through a Yukawa coupling, which is a characteristic feature of the Abelian extensions of the SM, allows for a new and interesting possibility of producing a heavy neutrino pair from the SM-like Higgs (besides the obvious heavy Higgs mode). The interaction between the light SM-like Higgs and the heavy neutrinos is not suppressed by the mixing angle Vαi but is controlled by the Yukawa coupling YN and the scalar mixing angle α. For illustrative purposes we assume that the PMNS matrix is equal to the identity matrix and that both neutrino masses, light and heavy, are degenerate in flavour In this case the elements of the neutrino mixing matrix Vαi are given by mD/M ≃
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