Multi- Z′ signatures of spontaneously broken local U(1)′ symmetry

We discuss multi-Z′ signatures coming from decays of Higgs bosons in models with a spontaneously broken U(1)′ symmetry, which can be observed as “lepton jets” or multilepton final states depending on the mass range of new bosons. We consider anomaly-free U(1)′ models without introducing new fermions except for right-handed neutrinos, in which the Higgs sector is composed of an isospin doublet and a singlet fields with zero and nonzero U(1)′ charges, respectively. The multi-Z′ signatures can then be obtained via the decays of the discovered (extra) Higgs boson h (ϕ), i.e., h→Z′Z′, ϕ→Z′Z′, and/or h→ϕϕ→4Z′ as far as kinematically allowed. We give the upper limit on the branching ratios of h into Z′Z′ and 4Z′ from the current experimental data in each model. We also show the deviation in the hhh coupling from the standard model prediction at one-loop level, and find that its amount is typically smaller than 1%. Published by the American Physical Society 2025