Higgs singlet boson as a diphoton resonance in a vector-like quark model

TL;DR

This paper proposes that a Higgs singlet, produced via gluon fusion in a vector-like quark model, can explain the 750 GeV diphoton excess observed at the LHC, with specific predictions for its properties and related flavor-changing processes.

Contribution

It introduces a Higgs singlet in a vector-like quark framework to explain the diphoton excess, providing detailed predictions for its production, decay, and related flavor physics constraints.

Findings

Higgs singlet width below 1 GeV

Diphoton production cross section around 1 pb

Branching ratio to diphoton approximately 0.017

Abstract

ATLAS and CMS recently show the first results from run 2 of the Large Hadron Collider (LHC) at $\sqrt{s}=13$ TeV. A resonant bump at a mass of around 750 GeV in the diphoton invariant mass spectrum is indicated and the corresponding diphoton production cross section is around 3-10 fb. Motivated by the LHC diphoton excess, we propose that the possible resonance candidate is a Higgs singlet. To produce the Higgs singlet via gluon-gluon fusion process, we embed the Higgs singlet in the framework of vector-like triplet quark (VLTQ) model. As a result, the Higgs singlet decaying to diphoton final state is via VLTQ loops. Using the enhanced number of new quarks and new Yukawa couplings of the VLTQs and Higgs singlet, we successfully explain the diphoton production cross section. We find that the width of the Higgs singlet is below 1 GeV, its production cross section can be of order of 1 pb at $\sqrt{s}=13$ TeV, and the branching ratio for it decaying to diphoton is around $0.017$ and is insensitive to the masses of VLTQs and new Yukawa couplings. We find a strong correlation between the Higgs Yukawa couplings to $s$-$b$ and $c$-$t$; the resulted branching ratio for $t \to c h$ can be $1.1\times 10^{-4}$ when the constraint from $B_s$ oscillation is applied. With the constrained parameter values, the signal strength for the SM Higgs decaying to diphoton is $\mu_{\gamma\gamma}< 1.18$, which is consistent with the current measurements at ATLAS and CMS.