Decay of Z into Three Pseudoscalar Bosons

We consider the decay of the $Z$ boson into three pseudoscalar bosons in a general two-Higgs-doublet model. Assuming $m_A$ to be very small, and that of the two physical neutral scalar bosons $h_1$ and $h_2$, $A$ only couples to $Z$ through $h_1$, we find the $Z \to A A A$ branching fraction to be negligible for moderate values of $\tan \beta \equiv v_2/v_1$, if there is no $\lambda_5 (\Phi_1^\dagger \Phi_2)^2 + h.c.$ term in the Higgs potential; otherwise there is no absolute bound but very large quartic couplings (beyond the validity of perturbation theory) are needed for it to be observable.Comment: 8 pages including 1 fi

Exceeding the MSSM Higgs Mass Bound in a Special Class of U(1) Gauge Models

A special class of supersymmetric U(1) gauge extensions of the standard model was proposed in 2002. It is anomaly-free, has no mu term, and conserves baryon and lepton numbers automatically. It also allows the lightest Higgs boson to have a mass exceeding the MSSM (Minimal Supersymmetric Standard Model) bound, i.e. about 130 GeV, which is of current topical interest from LHC (Large Hadron Collider) data. This and other new aspects of this 2002 proposal are discussed.Comment: 10 pages, 2 tables, version to appear in PL

Seeding of Strange Matter with New Physics

At greater than nuclear densities, matter may convert into a mixture of nucleons, hyperons, dibaryons, and strangelets, thus facilitating the formation of strange matter even before the onset of the quark-matter phase transition. From a nonstrange dibaryon condensate, it may even be possible to leapfrog into strange matter with a certain new interaction, represented by an effective six-quark operator which is phenomenologically unconstrained.Comment: 7 pages, no figure (Talk given at SQM97

Spontaneous Supersymmetric Generation of an Indeterminate Mass Scale and a Possible Light Sterile Neutrino

If a global continuous symmetry of a supersymmetric field theory is spontaneously broken while preserving the supersymmetry, the resulting theory has a massless superfield. One of its two bosonic degrees of freedom is the familiar phase rotation of the usual massless Nambu-Goldstone boson, but the other is a scale transformation. An indeterminate mass scale is thus generated. In the fermion sector, a seesaw texture appears which may be suitable for a possible light sterile neutrino. This feature persists even after the gauging of the continuous symmetry or the breaking of the supersymmetry to resolve the aforementioned mass-scale ambiguity.Comment: 9 pages, expanded to include the discussion of a possible sterile neutrin

Multiplicative Conservation of Baryon Number and Baryogenesis

In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe. A parallel possibility, hitherto unrecognized, also holds for baryon number and baryogenesis. This new idea is shown to be naturally realized in the context of a known supersymmetric string-inspired extension of the Standard Model, based on E(6) particle content, and having an extra U(1)_N gauge symmetry. Within this framework, two-loop radiative neutrino masses are also possible, together with a new form of very long-lived matter.Comment: 9 pages, 4 figures, 3 table

Revelations of the E_6/U(1)_N Model: Two-Loop Neutrino Mass and Dark Matter

The E_6/U(1)_N gauge extension of the Supersymmetric Standard Model, first proposed by Ma, is shown to have exactly the requisite ingredients to realize the important new idea that dark matter is the origin of neutrino mass. With the implementation of a discrete Z_2 X Z_2 symmetry, and particle content given by three {27} representations of E_6, neutrino masses are naturally generated in two loops, with candidates of dark matter in the loops. All particles of this model are expected to be at or below the TeV scale, allowing them to be observable at the LHC.Comment: 10 pages, 3 figure