Quark-universal $U(1)$ breaking scalar at the LHC

TL;DR

This paper explores a new scalar particle associated with a leptophobic $Z'$ gauge boson in a $U(1)$ extension, detailing its production mechanisms, decay channels, and potential signals at the LHC.

Contribution

It introduces the concept of a quark-universal $U(1)$ breaking scalar and analyzes its production and decay modes, especially in the leptophobic $Z'$ scenario, highlighting novel detection prospects.

Findings

Scalar can be produced with $Z'$ or via $Z'$ fusion at LHC.

Decays mainly into four jets or two photons.

Diphoton resonance as a promising discovery channel.

Abstract

If the quarks or leptons are charged under a new $U(1)$ gauge symmetry, then besides a $Z'$ boson there must exist at least one new boson whose decay products include Standard Model particles. In the case of a minimal symmetry breaking sector, that new boson is a scalar $\phi$ that couples to the $Z'$ boson as well as to the new fermions required to cancel the $U(1)$ gauge anomalies. The scalar may be produced at the LHC in association with a $Z'$ boson, or through $Z'$ boson fusion, while its decays are typically into four jets or two photons. We analyze in detail the case where the $Z'$ boson is leptophobic, and all the quarks have the same charge under the new $U(1)$. If $\phi$ mixes with the Standard Model Higgs boson, then the new scalar can also be produced via gluon fusion, and the discovery mode is likely to be a diphoton resonance.