Z ′, Higgses and heavy neutrinos in U(1)′ models: from the LHC to the GUT scale

Abstract

We study a class of non-exotic minimal U(1) extensions of the Standard Model, which includes all scenarios that are anomaly-free with the ordinary fermion content augmented by one Right-Handed neutrino per generation, wherein the new Abelian gauge group is spontaneously broken by the non-zero Vacuum Expectation Value of an additional Higgs singlet field, in turn providing mass to a Z state. By adopting the B − L example, whose results can be recast into those pertaining to the whole aforementioned class, and allowing for both scalar and gauge mixing, we first extract the surviving parameter space in presence of up-to-date theoretical and experimental constraints. Over the corresponding parameter configurations, we then delineate the high energy behaviour of such constructs in terms of their stability and perturbativity. Finally, we highlight key production and decay channels of the new states entering the spectra of this class of models, i.e., heavy neutrinos, a second Higgs state and the Z , which are amenable to experimental investigation at the Large Hadron Collider. We therefore set the stage to establish a direct link between measurements obtainable at the Electro-Weak scale and the dynamics of the underlying model up to those where a Grand Unification Theory embedding a U(1) can be realised.

Constraining a general U(1)′ inverse seesaw model from vacuum stability, dark matter, and collider

“…The presence of the extra Z boson that couples to the quarks and the leptons also gives rise to a rich collider phenomenology in the U (1) models [20,22,[34][35][36][37]. Searches for such Z boson through it's decay dileptons have been conducted by the ATLAS and the CMS collaborations and lower limits on the Z mass has been obtained [38][39][40].…”

Extra Higgs boson and Z′ as portals to signatures of heavy neutrinos at the LHC

“…We shall see that two production mechanism will turn out to be useful, depending on the actual value of m ν h , namely, gg → H 2 → ν h ν h (for intermediate mass values in the range m H 1 /2 < m ν h < m H 2 /2) and qq → Z ′ → ν h ν h (for heavy mass values in the range m H 2 /2 < m ν h < M Z ′ /2). Notice in fact that the H 2 mass can be accessible at the LHC up to several hundreds of GeV while current limits on the Z ′ one are a few TeV [38][39][40].…”

“…Other parameterisations, with a non-canonical diagonalised kinetic Lagrangian and a diagonal covariant derivative, are, however, completely equivalent. The details of the kinetic mixing and its relation to the Z − Z ′ mixing, which we omit in this work, can be found in [9,40,41].…”

“…The Z − Z ′ mixing angle in the neutral gauge sector is strongly bounded indirectly by the EW Precision Tests (EWPTs) and directly by the LHC data [40,[42][43][44][45] to small values, i.e, |θ ′ | 10 −3 . In the B − L model under study, we find…”

“…In addition, as the Higgs mediated cross section depends on the scalar mixing angle, α, we take into account the exclusion limits on the α parameter as a function of the heavy Higgs mass and on the mass itself. Such limits have been enforced using HiggsBounds [47][48][49][50][51] and HiggsSignals [52] packages, see [40]. Given the allowed parameter space, we can compute the total cross sections for heavy neutrino production.…”