88 research outputs found
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
of the minimal model is induced by spontaneous breaking of the U(1)
symmetry.Comment: 10 pages, Revte
H/A Higgs Mixing in CP-Noninvariant Supersymmetric Theories
For large masses, the two heavy neutral Higgs bosons are nearly degenerate in
many 2--Higgs doublet models, and particularly in supersymmetric models. In
such a scenario the mixing between the states can be very large if the theory
is CP-noninvariant. We analyze the formalism describing this configuration, and
we point to some interesting experimental consequences.Comment: LaTeX, 1+20 pages, 6 figure
Electron and Neutron Electric Dipole Moments in the Focus Point Scenario of SUGRA Model
We estimate the electron and neutron electric dipole moments in the focus
point scenario of the minimal SUGRA model corresponding to large sfermion
masses and moderate to large . There is a viable region of moderate
fine-tuning in the parameter space, around , where the
experimental limits on these electric dipole moments can be satisfied without
assuming unnaturally small phase angles. But the fine-tuning constraints become
more severe for .Comment: 16 pages, LaTeX, 4 postscript figures. Very minor changes made in
only a few sentences for clarification. Final version to appear in Phys. Rev.
and processes with polarized muons and supersymmetric grand unified theories
and processes are
analyzed in detail with polarized muons in supersymmetric grand unified
theories. We first present Dalitz plot distribution for decay based on effective Lagrangian with general
lepton-flavor-violating couplings and define various P- and T-odd asymmetries.
We calculate branching ratios and asymmetries in supersymmetric SU(5) and
SO(10) models taking into account complex soft supersymmetry breaking terms.
Imposing constraints from experimental bounds on the electron, neutron and
atomic electric dipole moments, we find that the T-odd asymmetry for can be 15% in the SU(5) case. P-odd asymmetry with respect
to muon polarization for varies from -20% to -100%
for the SO(10) model while it is in the SU(5) case. We also show that
the P-odd asymmetries in and the ratio of
and branching
fractions are useful to distinguish different models.Comment: 52 pages, 15 figure
Discrete symmetries and isosinglet quarks in low-energy supersymmetry
Many extensions of the minimal supersymmetric standard model contain
superfields for quarks which are singlets under weak isospin with electric
charge -1/3. We explore the possibility that such isosinglet quarks have low or
intermediate scale masses, but do not mediate rapid proton decay because of a
discrete symmetry. By imposing the discrete gauge anomaly cancellation
conditions, we show that the simplest way to achieve this is to extend the Z_3
"baryon parity" of Ibanez and Ross to the isosinglet quark superfields. This
can be done in three distinct ways. This strategy is not consistent with grand
unification with a simple gauge group, but may find a natural place in
superstring-inspired models, for example. An interesting feature of this
scenario is that proton decay is absolutely forbidden.Comment: 13 pages, MIT-CTP-2345, NUB-3097-94T
CP violation in supersymmetric model with non-degenerate A-terms
We study the CP phases of the soft supersymmetry breaking terms in
string-inspired models with non-universal trilinear couplings. We show that
such non-universality plays an important role on all CP violating processes. In
particular these new supersymmetric sources of CP violation may significantly
contribute to the observed CP phenomena in kaon physics while respecting the
severe bound on the electric dipole moment of the neutron.Comment: 14 pages, Late
CP Violation In Single Top Production And Decay Via p p-bar -> t b-bar +X -> W^+ b b-bar +X Within The MSSM: A Possible Application For Measuring \arg(A_t) At Hadron Colliders
CP-nonconserving effects in the reaction p p-bar -> t b-bar +X -> W^+ b b-bar
+X, driven by the supersymmetric CP-odd phase of the stop trilinear soft
breaking term, \arg(A_t), are studied. We discuss the CP-nonconserving effects
in both production and the associated decay amplitudes of the top. We find
that, within a plausible low energy scenario of the MSSM and keeping the
neutron electric dipole moment below its current limit, a CP-violating
cross-section asymmetry as large as 2-3% can arise if some of the parameters
lie in a favorable range. A partial rate asymmetry originating only in the top
decay t -> W^+ b is found to be, in general, below the 0.1% level which is
somewhat smaller than previous claims. For a low \tan\beta of order one the
decay asymmetry can reach at the most ~0.3%. This (few) percent level overall
CP-violating signal in p p-bar -> t b-bar +X -> W^+ b b-bar +X might be within
the reach of the future 2(4) TeV pp-bar Tevatron collider that may be able to
produce ~10000(~30000) such tb-bar events with an integrated luminosity of 30
fb^{-1}. In particular, it may be used to place an upper bound on \arg(A_t) if
indeed \arg(\mu) -> 0, as implied from the present experimental limit on the
neutron electric dipole moment. The partial rate asymmetry in the top decay
(~few \times 10^{-3}) may also be within the reach of the LHC with ~10^7 pairs
of tt-bar produced, provided detector systematics are sufficiently small. We
also show that if the GUT-scale universality of the soft breaking trilinear
terms is relaxed, then the phases associated with \arg A_u and \arg A_d can
take values up to ~few \times 10^{-1} even with squarks and gluino masses of
several hundred GeV's without contradicting the experimental limit on the
neutron electric dipole moment.Comment: 39 pages, plain latex, 20 figures embadded in the text using epsfi
Moderate Supersymmetric CP Violation
It is well known that supersymmetry (SUSY) gives neutron and electron
electric dipole moments ( and ) which are too large by about
. If we assume a SUSY model cannot contain fine-tunings or large mass
scales, then one must require that the SUSY breaking mechanism give real soft
breaking parameters, in which case the minimal SUSY model has no violation
other than from the CKM matrix (besides possible strong violating
effects). We show that in non-minimal SUSY models, a moderate amount of
violation can be induced through one loop corrections to the scalar potential,
giving an effective phase of order , and thus implying and
can be near their current experimental bounds . This moderate amount
of SUSY violation could also prove important for models of electroweak
baryogenesis. We illustrate our results with a specific model.Comment: 19pp plain LATEX, 1 fig (by EMAIL request), TRI-PP-93-86. (Some
clarifying comments about renormalizability added--version to appear in Phys.
Rev. D
Anomalous U(1) as a mediator of Supersymmetry Breaking
We point out that an anomalous gauge U(1) symmetry is a natural candidate for
being the mediator and messenger of supersymmetry breaking. It facilitates
dynamical supersymmetry breaking even in the flat limit. Soft masses are
induced by both gravity and the U(1) gauge interactions giving an unusual mass
hierarchy in the sparticle spectrum which suppresses flavor violations. This
scenario does not suffer from the Polonyi problem.Comment: 8 pages, Latex. Some comments adde
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