Electroweak baryogenesis from chargino transport in the supersymmetric model

We study the baryon asymmetry of the universe in the supersymmetric standard model (SSM). At the electroweak phase transition, the fermionic partners of the charged SU(2) gauge bosons and Higgs bosons are reflected from or transmitted to the bubble wallof the broken phase. Owing to a physical complex phase in their mass matrix, these reflections and transmissions have asymmetries between CP conjugate processes. Equilibrium conditions in the symmetric phaseare then shifted to favor a non-vanishing value for the baryon number density, which is realized through electroweak anomaly. We show that the resultant ratio of baryon number to entropy is consistent with its present observed value within reasonable ranges of SSM parameters, provided that the CP-violating phase intrinsic in the SSM is not much suppressed. The compatibility with the constraints on the parameters from the electric dipole moment of the neutron is also discussed.Comment: 23 page

CPCP violation in minimal supersymmetric standard model

$CP$ violating phenomena predicted by the minimal supersymmetric standard model are discussed in a case where the $CP$ violating phases in SUSY sector are not suppressed. The electric dipole moments of the neutron and the electron are large, but can be smaller than their experimental upper bounds if the scalar quarks and leptons are heavier than a few TeV. $T$ violating asymmetries in the production processes of the different neutralino pair and the different chargino pair emerge at the tree level. They could be as large as of order $10^{-2}$ in unpolarized electron beam experiments and $10^{-1}$ in polarized electron beam experiments. In a pair production of the charginos of the same mass, the asymmetry emerges through the electric and the weak "electric" dipole moments of the charginos at the loop level, but its magnitude is at most of order $10^{-4}$.Comment: 7 pages with 7 figures, TKU-HEP 94/02; IFM 2/94, LaTeX with Elsevir Science Publisher's style file, espcrc2.sty. (To appear in the proceedings of the Third KEK Topical Conference on CP Violation, November 1993) Figures are not included. The complete PostScript file can be obtained by anonymous ftp from ape.sp.u-tokai.ac.jp in the directr

Supersymmetric Extension of the Standard Model with Naturally Stable Proton

A new supersymmetric standard model based on N=1 supergravity is constructed, aiming at natural explanation for the proton stability without invoking an ad hoc discrete symmetry through R parity. The proton is protected from decay by an extra U(1) gauge symmetry. Particle contents are necessarily increased to be free from anomalies, making it possible to incorporate the superfields for right-handed neutrinos and an SU(2)-singlet Higgs boson. The vacuum expectation value of this Higgs boson, which induces spontaneous breakdown of the U(1) symmetry, yields large Majorana masses for the right-handed neutrinos, leading to small masses for the ordinary neutrinos. The linear coupling of SU(2)-doublet Higgs superfields, which is indispensable to the superpotential of the minimal supersymmetric standard model, is replaced by a trilinear coupling of the Higgs superfields, so that there is no mass parameter in the superpotential. The energy dependencies of the model parameters are studied, showing that gauge symmetry breaking is induced by radiative corrections. Certain ranges of the parameter values compatible with phenomena at the electroweak energy scale can be derived from universal values of masses-squared and trilinear coupling constants for scalar fields at a very high energy scale.Comment: 32 pages, Revtex, 7 figure

A Supersymmetric Model with an Extra U(1) Gauge Symmetry

In the standard model the proton is protected from decay naturally by gauge symmetries, whereas in the ordinary minimal supersymmetric standard model an ad hoc discrete symmetry is imposed for the proton stability. We present a new supersymmetric model in which the proton decay is forbidden by an extra U(1) gauge symmetry. Particle contents are necessarily increased to be free from anomalies, incorporating right-handed neutrinos. Both Dirac and Majorana masses are generated for neutrinos, yielding non-vanishing but small masses. The superpotential consists only of trilinear couplings and the mass parameter $\mu$ of the minimal model is induced by spontaneous breaking of the U(1) symmetry.Comment: 10 pages, Revte

Effects of supersymmetric grand unification scale physics on Γ(b→sγ)\Gamma \left( b\to s\gamma\right)

Although calculations of the $b\rightarrow s\gamma$ rate in supersymmetric grand unified models have always either ignored the gluino mediated contribution or found it to be negligible, we show that taking universal supersymmetry breaking masses at the Planck scale, rather than at the gauge unification scale as is customary, leads to the gluino contribution being more significant and in fact sometimes even larger than the chargino mediated contributions when $\mu >0$ and $\tan{\beta}$ is of order 1. The impact is greatest felt when the gluinos are relatively light. Taking the universal boundary condition at the Planck scale also has an effect on the chargino contribution by increasing the effect of the wino and higgsino-wino mediated decays. The neutralino mediated contribution is found to be enhanced, but nevertheless it remains relatively insignificant.Comment: Title changed, final version as accepted for PRD, 12 pages, 6 Figures (Figs.2-6 included, uuencoded, epsf.tex

Large effects on \BsBs mixing by vector-like quarks

We calculate the contributions of the vector-like quark model to \BsBs mixing, taking into account the constraints from the decay $B\to X_s\gamma$. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However, \BsBs mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In sizable ranges of the model parameters, the mixing parameter $x_s$ is much different from the standard model prediction.Comment: 11 pages, 4 figures, To be published in Phys. Rev.

Visible Sector Supersymmetry Breaking Revisited

We revisit the possibility of "visible sector" SUSY models: models which are straightforward renormalizable extensions of the Minimal Supersymmetric Standard Model (MSSM), where SUSY is broken at tree level. Models of this type were abandoned twenty years ago due to phenomenological problems, which we review. We then demonstrate that it is possible to construct simple phenomenologically viable visible sector SUSY models. Such models are indeed very constrained, and have some inelegant features. They also have interesting and distinctive phenomenology. Our models predict light gauginos and very heavy squarks and sleptons. The squarks and sleptons may not be observable at the LHC. The LSP is a stable very light gravitino with a significant Higgsino admixture. The NLSP is mostly Bino. The Higgs boson is naturally heavy. Proton decay is sufficently and naturally suppressed, even for a cutoff scale as low as 10^8 GeV. The lightest particle of the O'Raifeartaigh sector (the LOP) is stable, and is an interesting cold dark matter candidate.Comment: 23 pages, 3 figures, LaTe

Neutrino Mass and Grand Unification

Seesaw mechanism appears to be the simplest and most appealing way to understand small neutrino masses observed in recent experiments. It introduces three right handed neutrinos with heavy masses to the standard model, with at least one mass required by data to be close to the scale of conventional grand unified theories. This may be a hint that the new physics scale implied by neutrino masses and grand unification of forces are one and the same. Taking this point of view seriously, I explore different ways to resolve the puzzle of large neutrino mixings in grand unified theories such as SO(10) and models based on its subgroup $SU(2)_L\times SU(2)_R\times SU(4)_c$.Comment: 17 pages, 5 figures; Invited talk at the Nobel Symposium 129 on Neutrinos at Haga Slott, Sweden, August, 200