Theory and phenomenology of an exceptional supersymmetric standard model

Abstract

We make a comprehensive study of the theory and phenomenology of a low energy supersymmetric standard model originating from a string-inspired E 6 grand unified gauge group. The Exceptional Supersymmetric Standard Model (ESSM) considered here is based on the low energy SM gauge group together with an extra Z ′ corresponding to an extra U (1) N gauge symmetry under which right-handed neutrinos have zero charge. The low energy matter content of the ESSM corresponds to three 27 representations of the E 6 symmetry group, to ensure anomaly cancellation, plus an additional pair of Higgs-like doublets as required for high energy gauge coupling unification. The ESSM is therefore a low energy alternative to the MSSM or NMSSM. The ESSM involves extra matter beyond the MSSM contained in three 5 + 5 * representations of SU (5), plus three SU (5) singlets which carry U (1) N charges, one of which develops a VEV, providing the effective µ term for the Higgs doublets, as well as the necessary exotic fermion masses. We explore the RG flow of the ESSM and examine theoretical restrictions on the values of new Yukawa couplings caused by the validity of perturbation theory up to the Grand Unificationscale. We then discuss electroweak symmetry breaking and Higgs phenomenology, and establish an upper limit on the mass of the lightest Higgs particle which can be significantly heavier than in the MSSM and NMSSM, in leading two-loop approximation. We also discuss the phenomenology of the Z ′ and the extra matter, whose discovery will provide a smoking gun signal of the model.

Three-Higgs-doublet models: symmetries, potentials and Higgs boson masses

“…with three up-type and down-type Higgs families including MSSM where both Higgs types transform as triplets of A 4 [20] and a version of the E 6 SSM [21,22] where both Higgs types transform as triplets of ∆ (27) [23]. In both these examples, only the Higgs fields of the third family are (predominantly) assumed to develop VEVs which motivates the vacuum alignment (0, 0, v).…”

LHC signatures of the constrained exceptional supersymmetric standard model

“…Right-handed neutrinos N c i should be associated with the last term in Eq. (1), (1,0) i . The next-to-last term in Eq.…”

“…To be precise, the ordinary SM families which contain the doublets of left-handed quarks Q i and leptons L i , right-handed up-and down-quarks (u c i and d c i ) as well as right-handed charged leptons, are assigned to (10,1) i + (5 * , 2) i . Right-handed neutrinos N c i should be associated with the last term in Eq.…”

“…On the other hand the LHC can relatively quickly discover new coloured particles and a Z ′ if these states are kinematically accessible. In this article we study the production and decay signatures of the Z ′ and exotic colour triplet charge 1/3 fermions, which we refer to as D-fermions, that naturally appear within well a motivated supersymmetric extension of the SM known as the Exceptional Supersymmetric Standard Model (E 6 SSM) [1].…”

“…An extra U(1) ′ gauge group can also be motivated within the framework of grand unified theories (GUTs), arising as the relic of the breakdown of the unified gauge group. For example, an E 6 GUT symmetry can be broken to the rank-5 subgroup SU(3) C ×SU(2) L ×U(1) Y ×U(1) ′ where in general U(1) ′ = U(1) χ cos θ+U(1) ψ sin θ [6], and the two anomaly-free U(1) ψ and U(1) χ symmetries originate from the breakings 1 Note that we will not put hats on the superfields.…”