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

Stephen F King,Roman Nevzorov

doi:10.1007/jhep03(2016)139

Abstract

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 S1,2 arising from the three 27-dimensional representations of E6. The three 27s also contain three copies of colour-triplet charge ∓1/3 vector-like fermions D,$$ \overline{D} $$ D ¯ and two copies of charged inert Higgsinos $$ {\tilde{H}}^{+} $$ H ˜ + ,$$ {\tilde{H}}^{-} $$ H ˜ − to which the singlets S1,2 may couple. We propose a variant of the E6SSM where the third singlet S3 breaks a gauged U(1)N above the TeV scale, predicting Z N ′ , D,$$ \overline{D} $$ D ¯ , $$ {\tilde{H}}^{+} $$ H ˜ + ,$$ {\tilde{H}}^{-} $$ H ˜ − at LHC Run 2, leaving the two lighter singlets S1,2 with masses around 750 GeV. We calculate the branching ratios and cross-sections for the two scalar and two pseudoscalar states associated with the S1,2 singlets, including possible degeneracies and maximal mixing, subject to the constraint that their couplings remain perturbative up to the unification scale.

Highlights

JHEP03(2016)139 the 750 GeV diphoton resonance [158]
We propose a variant of the E6SSM where the third singlet S3 breaks a gauged U(1)N above the TeV scale, predicting ZN, D, D, H +, H − at LHC Run 2, leaving the two lighter singlets S1,2 with masses around 750 GeV
An example of a model with singlets and extra vector-like matter is the Exceptional Supersymmetric (SUSY) Standard Model (E6SSM) [159, 160], where the spectrum of the MSSM is extended to fill out three complete 27-dimensional representations of the gauge group E6 which is broken at the unification scale down to the SM gauge group plus an additional gauged U(1)N symmetry at low energies under which right-handed neutrinos are neutral, allowing them to get large masses

Summary

A variant of the E6SSM

We first recall that the E6SSM [159, 160] may be derived from an E6 GUT group broken via the following symmetry breaking chain: E6 → SO(10) ⊗ U(1)ψ → SU(5) ⊗ U(1)χ ⊗ U(1)ψ → SU(3) ⊗ SU(2) ⊗ U(1)Y × U(1)χ ⊗ U(1)ψ → SU(3) ⊗ SU(2) ⊗ U(1)Y ⊗ U(1)N. Turning to a discussion of the 750 GeV diphoton excess recently observed by ATLAS and CMS in the framework of the variant of the E6SSM discussed, whose effective superpotential is given by eq (2.10) This SUSY model involves two SM singlet superfields S1,2 plus a set of extra vector-like supermultiplets beyond the MSSM, including two pairs of inert Higgs doublets (Hαd and Hαu), as well as three generations of exotic quarks Di and Di with electric charges ∓1/3. 3.2 Two degenerate scalar/pseudoscalar case let us assume that there are two superfields S1 and S2 that have sufficiently large Yukawa couplings to the exotic quark and inert Higgsino states and can contribute to the measured cross section pp → γγ. It seems rather problematic to achieve any enhancement of the signal in the diphoton channel in the scenario when all Yukawa couplings are equal or reasonably close to each other

Maximal mixing scenario

Conclusions