Diphoton Excess at 750 GeV in leptophobic U(1)$^\prime$ model inspired by $E_6$ GUT

TL;DR

This paper proposes a leptophobic U(1)′ extension of the Standard Model inspired by E6 GUT to explain the 750 GeV diphoton excess observed at the LHC, involving new fermions and scalar fields.

Contribution

It introduces a novel U(1)′ model with anomaly-free extra fermions and a scalar that accounts for the diphoton excess through gluon fusion and loop decays.

Findings

The scalar h_Φ can be produced via gluon fusion at the LHC.

h_Φ decays into diphotons through loops of new fermions.

The model allows for dark matter and scalar decay channels.

Abstract

We discuss the 750 GeV diphoton excess at the LHC@13TeV in the framework of leptophobic U(1)$^\prime$ model inspired by $E_6$ grand unified theory (GUT). In this model, the Standard Model (SM) chiral fermions carry charges under extra U(1)$^\prime$ gauge symmetry which is spontaneously broken by a U(1)$^\prime$-charged singlet scalar ($\Phi$). In addition, extra quarks and leptons are introduced to achieve the anomaly-free conditions, which is a natural consequence of the assumed $E_6$ GUT. These new fermions are vectorlike under the SM gauge group but chiral under new U(1)$^\prime$, and their masses come entirely from the nonzero vacuum expectation value of $\Phi$ through the Yukawa interactions. Then, the CP-even scalar $h_\Phi$ from $\Phi$ can be produced at the LHC by the gluon fusion and decay to the diphoton via the one-loop diagram involving the extra quarks and leptons, and can be identified as the origin of diphoton excess at 750 GeV. In this model, $h_\Phi$ can decay into a pair of dark matter particles as well as a pair of scalar bosons, thereby a few tens of the decay width may be possible.