Abstract
We consider a class of minimal anomaly free $\mathrm{U}(1)$ extensions of the Standard Model with three generations of right-handed neutrinos and a complex scalar. Using electroweak precision constraints, new 13 TeV LHC data, and considering theoretical limitations such as perturbativity, we show that it is possible to constrain a wide class of models. By classifying these models with a single parameter, $\kappa$, we can put a model independent upper bound on the new $\mathrm{U}(1)$ gauge coupling $g_z$. We find that the new dilepton data puts strong bounds on the parameters, especially in the mass region $M_{Z'}\lesssim 3~ \mathrm{TeV}$.
Highlights
Using 13 TeV dilepton resonance search data [33]
The assumptions of our approach are (i) the existence of an additional U(1) gauge group which is broken by the vacuum expectation value (VEV) of a complex scalar, (ii) the SM fermions are the only fermions that are charged under the SM gauge group, (iii) there are three generations of right-handed neutrinos which are SM singlets but charged under the new U(1), (iv) the right-handed neutrinos obtain masses via a Type-I seesaw scenario, (v) the gauge charges are generation independent, and (vi) the electroweak symmetry breaking (EWSB) occurs as in the SM
The relevant parameters are the mass of the new gauge boson MZ, U(1)z gauge coupling gz, and the κ parameter; this parametrization is viable for all κ values except for κ = 1/4
Summary
We consider the spontaneous symmetry breaking of U(1)z by an SM singlet complex scalar field φ that acquires a VEV vφ. The Higgs doublet Φ responsible for EWSB can in general be charged under U(1)z This leads to a mixing between the Z and Z bosons after symmetry breaking. It is possible to use the MZ-equation in (2.5) to express a third parameter in terms of MZ (and other SM parameters) and the two remaining free parameters. Instead one should really use the BSM mass relation of MZ in eq (2.5) which induces a tree level contribution to the oblique parameters. We can employ the parametrization of eq (2.7) together with eq (2.4) to express the mixing angle θ as a function of MZ , zH and gz; we express MZ in terms of these parameters
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