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

TL;DR

This paper explores multi-$Z'$ signatures from Higgs decays in models with a spontaneously broken $U(1)'$ symmetry, highlighting potential collider signals like lepton jets and analyzing deviations in Higgs self-coupling.

Contribution

It introduces anomaly-free $U(1)'$ models with specific Higgs sectors and provides predictions for multi-$Z'$ signatures and their experimental constraints.

Findings

Upper limits on Higgs decay branching ratios into $Z'$ pairs from current data.

Predicted deviations in the $hhh$ coupling are typically below 1%.

Multi-$Z'$ signatures can manifest as lepton jets or multi-lepton final states.

Abstract

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 multi-lepton 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 non-zero $U(1)'$ charges, respectively. The multi-$Z'$ signatures can then be obtained via the decays of the discovered (extra) Higgs boson $h$ ($\phi$), i.e., $h\to Z'Z'$, $\phi \to Z'Z'$ and/or $h \to \phi\phi \to 4Z'$ 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\%.