Effects of Family Nonuniversal Z' Boson on Leptonic Decays of Higgs and Weak Bosons

TL;DR

This paper investigates how a family-nonuniversal Z' boson could influence leptonic decays of the Higgs, Z, and W bosons, potentially revealing new physics beyond the standard model through current and future experiments.

Contribution

It provides a model-independent analysis of Z' effects on leptonic decays, considering existing constraints and exploring potential observable deviations in Higgs and gauge boson decays.

Findings

Z' effects can alter Higgs leptonic decays by a few percent or more.

Current data allows significant Z' contributions within experimental constraints.

Future collider measurements could detect or further constrain Z' couplings.

Abstract

Though not completely a surprise according to the standard model and existing indirect constraints, the Higgs-like particle, h, of mass around 125 GeV recently observed at the LHC may offer an additional window to physics beyond the standard model. In particular, its decay pattern can be modified by the existence of new particles. One of the popular scenarios involves a Z' boson associated with an extra Abelian gauge group. In this study, we explore the potential effects of such a boson with family-nonuniversal couplings on the leptonic decays of h, both flavor-conserving and flavor-changing. For current constraints, we take into account leptonic decays at the Z pole, LEP II scattering data, limits on various flavor-changing lepton transitions, and lepton magnetic dipole moments. Adopting a model-independent approach and assuming that the Z' has negligible mixing with the Z boson, we find that present data allow the Z' effects to reach a few percent or higher on h decays into a pair of leptons. Future measurements on h at the LHC or a linear collider can therefore detect the Z' contributions or impose further constraints on its couplings. We also consider Z'-mediated four-lepton decays of the Z and W bosons.