E. Keith

Generic consequences of a supersymmetric U(1) gauge factor at the TeV scale

We consider an arbitrary supersymmetric U(1) gauge factor at the TeV scale, under which the two Higgs superfields H{sub 1,2} of the standard model are nontrivial. We assume that there is a singlet superfield S such that H{sub 1}H{sub 2}S is an allowed term in the superpotential. We discuss first the generic consequences of this hypothesis on the structure of the two-doublet Higgs sector at the electroweak energy scale, as well as Z-Z{sup {prime}} mixing and the neutralino sector. We then assume the existence of a grand unified symmetry and universal soft supersymmetry-breaking terms at that scale. We further assume that the additional U(1) is broken radiatively via a superpotential term of the form hh{sup c}S, where h and h{sup c} are exotic color-triplet fields which appear in E{sub 6} models. We show that the U(1)-breaking scale and the parameter tan{beta}{equivalent_to}v{sub 2}/v{sub 1} are then both predicted as functions of the H{sub 1}H{sub 2}S coupling. {copyright} {ital 1997} {ital The American Physical Society}

Efficacious extra U(1) factor for the supersymmetric standard model

The totality of neutrino-oscillation phenomena appears to require the existence of a light singlet neutrino. As pointed out recently, this can be naturally accommodated with a specific extra U(1) factor contained in the superstring-inspired E{sub 6} model and its implied particle spectrum. We analyze this model for other possible consequences. We discuss specifically the oblique corrections from {ital Z}-{ital Z}{sup {prime}} mixing, the phenomenology of the two-Higgs-doublet sector, and the associated neutralino sector, as well as possible scenarios of gauge-coupling unification. {copyright} {ital 1996 The American Physical Society.}

Mutual consideration of b → sγ and μ → eγ in supersymmetric SO(10) grand unification☆

Abstract We compare the branching ratios for b → sγ and μ → eγ in terms of constraining the parameter space in supersymmetric SO(10) grand unification models where supersymmetry is broken softly near the Planck scale by generationally symmetric operators. We observe two general cases. One with small tan β = 2 and the other one with large tan β having third generation Yukawa coupling unification at the GUT scale. We show that for small tan β the branching ratio constraints allow only a smaller region of parameter space for μ > 0 compared to μ 0 parameter space is found to be given by the b → sγ branching ratio, while for large tan β with μ μ → eγ branching ratio. In many of these acceptable regions, we find that the μ → eγ branching ratio is predicted to be within one order of magnitude of its current experimental bound. We also show that the usually neglected gluino mediated diagrams in b → sγ can not be ignored in some regions of parameter space, especially for large tan β scenarios when the gluino mass is near its lower experimental bound.

Decay of Z into two light Higgs bosons.

If the standard electroweak gauge model is extended to include two or more Higgs doublets, there may be a neutral Higgs boson {ital h} which is light (with a mass of say 10 GeV) but the {ital hZZ} coupling is suppressed so that it has so far escaped experimental detection. However, the effective {ital hhZZ} coupling is generally unsuppressed; hence, the decay of {ital Z} into two light Higgs bosons plus a fermion-antifermion pair may have an observable branching fraction, especially if {ital h} decays invisibly as, for example, in the recently proposed doublet Majoron model.

OBLIQUE S AND T PARAMETERS AND LEPTOQUARK MODELS OF THE HERA EVENTS

If the recently discovered anomalous events at HERA are due to a scalar leptoquark, then it is very likely to have weak isospin

Decay of Z into three pseudoscalar bosons

I = 1/2

Supersymmetry and the spontaneous breaking of a U(1) gauge factor

. In that case, present precision measurements of the oblique radiative parameters

Electric dipole moments and b-τ unification in the presence of an intermediate scale in SUSY grand unification

S

Effects of supersymmetric grand unification scale physics on Gamma (b-->s gamma ).

and

Intermediate scale as a source of lepton flavor violation in SUSY SO(10)

T