Top FCNC induced by a Z' boson

TL;DR

This paper explores a Z' model where the Z' boson couples exclusively to up and top quarks, leading to flavor-changing neutral currents that can be tested through specific top quark production processes at the LHC.

Contribution

It introduces a simple family-dependent U(1)' model with right-handed up-type quark couplings, analyzing its implications for top FCNCs and proposing experimental probes.

Findings

Same sign top quark pair production constrains FCNCs

Triple top production is a sensitive probe

Dijet production at LHC tests Z' properties

Abstract

We consider a Z' model where the Z' boson couples only to up and top quarks. As a simple setup, one can consider a family-dependent $U(1)'$ symmetry, under which only right-handed up-type quarks are charged. After symmetry breaking, the right-handed quarks mix with each other and top flavor-changing neutral currents (FCNCs) mediated by the Z' boson can be generated at tree level. We take into account several processes to probe the top FCNCs, and find that the same sign top quark pair production or the triple top quark production is the most capable of testing the top FCNCs. We also consider a few non-FCNC processes to probe the Z' boson, for example, dijet production at the LHC.