Searching for $Z^{'}$ Gauge Boson in an Anomaly-Free U(1)$'$ Gauge Family Model

TL;DR

This paper investigates a simple, anomaly-free $Z'$ gauge boson model with family-dependent charges, analyzing its collider constraints and potential to explain the top quark forward-backward asymmetry.

Contribution

It introduces a UV-complete $Z'$ model with specific family charge assignments and explores its phenomenology in collider experiments and top quark asymmetry.

Findings

LHC dijet and dilepton data constrain $Z'$ mass and couplings.

The $Z'$ can contribute to top quark asymmetry within experimental bounds.

Flavor-changing effects are considered in the model's implications.

Abstract

We study a simple ultraviolet(UV) complete and anomaly free $Z'$ model based on a U$(1)'$ gauge family symmetry without introducing extra fermions beyond the standard model. The U$(1)'$ group is diagonal in the three family space in which the U(1)$'$ charges of the first and second families are the same but different from those of the third family. After spontaneous symmetry breaking and rotating to the mass eigenstates of quarks and leptons, there exist in general both flavor-conserving and flavor-changing couplings. In flavor conserving case, we use the latest dijet and dilepton search at the LHC to constrain the mass and gauge couplings of $Z'$. Also we show that in the flavor-changing and left-right asymmetry case, the t-channel $Z'$ process can only contribute to part of the forward-backward asymmetry in the top quark pair production observed at the Tevatron by taking into account the constraint from same sign top production at the LHC.