Realizing dark matter and Higgs inflation in light of LHC diphoton excess

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 chi providing a natural dark matter (DM) candidate. The real component of S serves as the new resonance (750GeV) 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) -> chi chi at the LHC Run-2. We further derive the DM relic density bound, and analyze constraints from the direct and indirect DM detections. (C) 2016 The Authors. Published by Elsevier B.V.National Natural Science Foundation of China [11275101, 11135003]; National Basic Research Program [2010CB833000]; Tsinghua University [20141081211]SCI(E)ARTICLEgesf02@gmail.com; hjhe@tsinghua.edu.cn; jren@physics.utoronto.ca; xianyu@cmsa.fas.harvard.edu480-49275