Exo-Higgs at 750 GeV and Genesis of Baryons

We propose that the diphoton excess at 750 GeV reported by ATLAS and CMS is due to the decay of an ${\it exo-Higgs}$ scalar $η$ associated with the breaking of a new $SU(2)_e$ symmetry, dubbed ${\it exo-spin}$. New fermions, ${\it exo-quarks}$ and ${\it exo-leptons}$, get TeV-scale masses through Yukawa couplings with $η$ and generate its couplings to gluons and photons at 1-loop. The matter content of our model yields a $B-L$ anomaly under $SU(2)_e$, whose breaking we assume entails a first order phase transition. A non-trivial $B-L$ asymmetry may therefore be generated in the early universe, potentially providing a baryogenesis mechanism through the Standard Model (SM) sphaleron processes. The spontaneous breaking of $SU(2)_e$ can in principle directly lead to electroweak symmetry breaking, thereby accounting for the proximity of the mass scales of the SM Higgs and the exo-Higgs. Our model can be distinguished from those comprising a singlet scalar and vector fermions by the discovery of TeV scale exo-vector bosons, corresponding to the broken $SU(2)_e$ generators, at the LHC.

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