The 750 GeV S -cion: Where else should we look for it?

Abstract

The resonance S at ∼750 GeV in the diphoton channel observed by ATLAS and CMS, if it holds up, is almost certainly the (S)cion of a larger dynasty in a UV completion that may very well be connected to the hierarchy problem. At this stage, however, an effective field theory framework provides a useful way to parametrize searches for this resonance in other channels. Assuming that the excess is due to a new scalar or pseudoscalar boson, we study associated production of S (“S-strahlung”) at the LHC and propose searches in several clean channels like γγℓℓ, γγℓE̸T and ℓℓℓγE̸T to probe dimension-5 operators coupling S to Standard Model gauge bosons. We consider a range of widths for S, from 5 GeV to 45 GeV, and find that the three channels probe complementary regions of parameter space and the suppression scale Λ. The finding of most immediate relevance is that with 3 fb−1, the LHC might already reveal new excesses in the γγℓℓ channel and a 5 (3) σ discovery may already be possible after collecting 65 (25) fb−1 of data with ℓℓℓγE̸T events if the scale of the new physics is within ∼9 TeV for couplings respecting 8 TeV LHC bounds and compatible with the observed excess in diphotons for a wide resonance as suggested by the ATLAS Collaboration. Beyond the EFT parametrization, we found realizations of models with heavy vector-like quarks and leptons which can simultaneously fit the diphoton excess and be discovered in the channels proposed here.