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

Abstract LHC Run-2 has provided intriguing di-photon signals of a new resonance around 750 GeV , 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 S and a doublet of vector-like quarks. The scalar sector respects CP symmetry, with its CP-odd imaginary component χ providing a natural dark matter (DM) candidate. The real component of S serves as the new resonance ( 750 GeV ) and explains the diphoton excess of the LHC Run-2. The new scalar degrees of freedom of S help to stabilize the Higgs vacuum, and can realize the Higgs inflation around GUT scale, consistent with the current cosmological observations. We construct two representative samples A and B of our model for demonstration. We study the mono-jet signals of DM production from invisible decays Re ( S ) → χ χ at the LHC Run-2. We further derive the DM relic density bound, and analyze constraints from the direct and indirect DM detections.