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.
Highlights
As another possibility, we can discuss a U(1) model, where the anomaly-free conditions are satisfied by introducing extra chiral fermions
Once we assume that the mixing is tiny, we can expect that hΦ mainly decays through the Yukawa couplings with the extra chiral fermions
In this paper we interpret the recently reported diphoton excess at 750 GeV in terms of a new singlet scalar boson hΦ that originates from spontaneous breaking of leptophobic U(1) embedded in E6 grand unification
Summary
We introduce our setup based on refs. [139, 140], where the SM gauge group is extended to include leptophobic U(1) gauge symmetry, and additional chiral fermions are introduced in order to cancel gauge anomalies. In order to realize electroweak symmetry breaking and U(1) breaking, we introduce scalars: two Higgs doublets, denoted by H1 and H2, and a U(1) -charged singlet, Φ Their quantum numbers are shown in table 1. The bosonic fields could be interpreted as the superpartners of the extra fermions, we have to consider an issue how to decouple the other bosonic fields except H1,2 and Φ, which is known to be notoriously difficult in any GUT models Another issue may be how to realize the U(1) in the low energy regime, our approach is bottom-up. We introduce only a minimal number of scalar fields in order to break the gauge symmetry spontaneously and generate masses for the SM and extra chiral fermions in our model, in such a way that the neutral Higgsmediated FCNC is not present at tree level [139]. Higgs doublets and Φ, together with the chiral fermions for the anomaly-free conditions, as shown in table 1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
