Realizing Dark Matter and Higgs Inflation in Light of LHC Diphoton Excess

TL;DR

This paper proposes a minimal extension of the Standard Model with a complex scalar and vector-like quarks to explain the 750GeV diphoton excess, while also addressing dark matter and Higgs inflation, consistent with cosmological data.

Contribution

It introduces a new scalar sector that accounts for the diphoton excess, stabilizes the Higgs vacuum, and enables Higgs inflation, linking collider signals with dark matter and cosmology.

Findings

The model explains the 750GeV diphoton resonance.

It provides a dark matter candidate consistent with relic density.

It supports Higgs inflation compatible with cosmological observations.

Abstract

LHC Run-2 has provided intriguing di-photon signals of a new resonance around 750GeV, which, if not due to statistical fluctuations, must call for new physics beyond the standard model (SM) at TeV scale. We propose a minimal extension of the SM with a complex singlet scalar $\mathcal{S}$ and a doublet of vector-like quarks. The scalar sector respects CP symmetry, with its CP-odd imaginary component $\chi$ providing a natural dark matter (DM) candidate. The real component of $\mathcal{S}$ serves as the new resonance (750GeV) and explains the diphoton excess of the LHC Run-2. The new scalar degrees of freedom of $\mathcal{S}$ help to stabilize the Higgs vacuum, and can realize the Higgs inflation around GUT scale, consistent with the current cosmology observations. We construct two representative samples A and B of our model for demonstration. We study the mono-jet signals of the DM production from invisible decays Re$(\mathcal{S}) \to \chi\chi$ at the LHC Run-2. We further derive the DM relic density bound, and analyze the constraints from direct and indirect DM detections.