750 GeV diphoton resonance from singlets in an exceptional supersymmetric standard model

Abstract

The 750-760 GeV diphoton resonance may be identified as one or two scalars and/or one or two pseudoscalars contained in the two singlet superfields S 1,2 arising from the three 27-dimensional representations of E 6. The three 27s also contain three copies of colour-triplet charge ∓1/3 vector-like fermions D, D¯¯¯¯ and two copies of charged inert Higgsinos H~+ , H~− to which the singlets S 1,2 may couple. We propose a variant of the E6SSM where the third singlet S 3 breaks a gauged U(1) N above the TeV scale, predicting Z N ′ , D, D¯¯¯¯, H~+ , H~− at LHC Run 2, leaving the two lighter singlets S 1,2 with masses around 750 GeV. We calculate the branching ratios and cross-sections for the two scalar and two pseudoscalar states associated with the S 1,2 singlets, including possible degeneracies and maximal mixing, subject to the constraint that their couplings remain perturbative up to the unification scale.