6,864 research outputs found
Collective treatment of High Energy Thresholds in SUSY - GUTs
Supersymmetric GUTs are the most natural extension of the Standard model
unifying electroweak and strong forces. Despite their indubitable virtues,
among these the gauge coupling unification and the quantization of the electric
charge, one of their shortcomings is the large number of parameters used to
describe the high energy thresholds (HET), which are hard to handle. We present
a new method according to which the effects of the HET, in any GUT model, can
be described by fewer parameters that are randomly produced from the original
set of the parameters of the model. In this way, regions favoured by the
experimental data are easier to locate, avoiding a detailed and time consuming
exploration of the parameter space, which is multidimensional even in the most
economic unifying schemes. To check the efficiency of this method, we directly
apply it to a SUSY SO(10) GUT model in which the doublet-triplet splitting is
realized through the Dimopoulos-Wilczek mechanism. We show that the demand of
gauge coupling unification, in conjunction with precision data, locates regions
of the parameter space in which values of the strong coupling \astrong are
within the experimental limits, along with a suppressed nucleon decay, mediated
by a higgsino driven dimension five operators, yielding lifetimes that are
comfortably above the current experimental bounds. These regions open up for
values of the SUSY breaking parameters m_0, M_1/2 < 1 TeV being therefore
accessible to LHC.Comment: 21 pages, 8 figures, UA-NPPS/BSM-10/02 (added
Eliminating the d=5 proton decay operators from SUSY GUTs
A general analysis is made of the question whether the d=5 proton decay
operators coming from exchange of colored Higgsinos can be completely
eliminated in a natural way in supersymmetric grand unified models. It is shown
that they can indeed be in SO(10) while at the same time naturally solving the
doublet-triplet splitting problem, having only two light Higgs doublets, and
using no more than a single adjoint Higgs field. Accomplishing all of this
requires that the vacuum expectation value of the adjoint Higgs field be
proportional to the generator I_{3R} rather than to B-L, as is usually assumed.
It is shown that such models can give realistic quark and lepton masses. We
also point out a new mechanism for solving the \mu problem in the context of
SO(10) SUSY GUTs.Comment: 24 pages in LaTeX, with 3 figure
Natural Gauge Hierarchy in SO(10)
It is shown that a natural gauge hierarchy and doublet-triplet splitting can
be achieved in SO(10) using the Dimopoulos-Wilczek mechanism. Artificial
cancellations (fine-tuning) and arbitrary forms of the superpotential are
avoided, the superpotential being the most general compatible with a symmetry.
It is shown by example that the Dimopoulos-Wilczek mechanism can be protected
against the effects of higher-dimension operators possibly induced by
Planck-scale physics. Natural implementation of the mechanism leads to an
automatic Peccei-Quinn symmetry. The same local symmetries that would protect
the gauge hierarchy against Planck-scale effects tend to protect the axion
also. It is shown how realistic quark and lepton masses might arise in this
framework. It is also argued that ``weak suppression'' of proton decay can be
implemented more economically than can ``strong suppression'', offering some
grounds to hope (in the context of SO(10)) that proton decay could be seen at
Superkamiokande.Comment: 26 pages in plain LaTeX, 5 figures available on request, BA-94-0
Reconfiguration with Simultaneous DG Installation to Improve the Voltage Profile in Distribution Network Using Harmony Search Algorithm
Due to dynamic nature of loads, total system load is more than its generation capacity that makes relieving of load on the feeders not possible and hence voltage profile of the system will not be improved to the required level. In order to meet required level of load demand, Reconfiguration & DG units are integrated in distribution network to improve voltage profile, to provide reliable and uninterrupted power supply and also to achieve economic benefits such as minimum power loss, energy efficiency and load leveling. This work proposes minimization of real power losses and improvement of voltage profile using network reconfiguration in the presence of distributed generation. Generally distributed generations (DG) are preferred with objective of minimizing real power loss and improving voltage profile in distribution system. In this work A meta heuristic Harmony Search Algorithm (HSA) is used to simultaneously reconfigure and identify the optimal locations for installation of DG units in a distribution network. Sensitivity analysis is used to identify optimal locations for installation of DG units. The proposed method has tested in MATLAB for 33-bus and 69- Bus radial distribution systems at three different load levels and the analysis is presented for loss minimization
Getting the Supersymmetric Unification Scale from Quantum Confinement with Chiral Symmetry Breaking
Two models which generate the supersymmetric Grand Unification Scale from the
strong dynamics of an additional gauge group are presented. The particle
content is chosen such that this group confines with chiral symmetry breaking.
Fields that are usually introduced to break the Grand Unified group appear
instead as composite degrees of freedom and can acquire vacuum expectation
values due to the confining dynamics. The models implement known solutions to
the doublet-triplet splitting problem. The SO(10) model only requires one
higher dimensional representation, an adjoint. The dangerous coloured
Higgsino-mediated proton decay operator is naturally suppressed in this model
to a phenomenologically interesting level. Neither model requires the presence
of gauge singlets. Both models are only technically natural.Comment: LaTex, 23 page
Flavor Symmetry L_mu - L_tau and quasi-degenerate Neutrinos
Current data implies three simple forms of the neutrino mass matrix, each
corresponding to the conservation of a non-standard lepton charge. While models
based on L_e and L_e - L_mu - L_tau are well-known, little attention has been
paid to L_mu - L_tau. A low energy mass matrix conserving L_mu - L_tau implies
quasi-degenerate light neutrinos. Moreover, it is mu-tau symmetric and
therefore (in contrast to L_e and L_e - L_mu - L_tau) automatically predicts
maximal atmospheric neutrino mixing and zero U_{e3}. A see-saw model based on
L_mu - L_tau is investigated and testable predictions for the neutrino mixing
observables are given. Renormalization group running below and in between the
see-saw scales is taken into account in our analysis, both numerically and
analytically.Comment: 15 pages, 2 figures. Prepared for 5th International Conference on
Nonaccelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun 200
Solar neutrinos and grand unification
We consider the Grand Unification (GU) scenario for neutrino masses which is
based on the see-saw mechanism with the mass of the heaviest right handed (RH)
neutrino at the GU-scale: , and on the quark-lepton
symmetry for fermions from the third generation. The scenario predicts for the
light neutrinos: eV and eV (in the case of a linear mass hierarchy of the RH neutrinos
or/and in presence of the Planck scale suppressed non-renormalizable
operators). It also predicts large mixing: . In this scenario the solar neutrinos
() undergo both the \nue \nutau resonance conversion in the
Sun and substantial \nue \numu vacuum oscillations on the way from the
Sun to the Earth. The interplay of both effects enlarges the range of neutrino
parameters which solve the -problem. In particular, mixing angle can be as small as the corresponding quark mixing:
. The scenario predicts
peculiar (oscillatory) distortion of the boron neutrino energy spectrum and
seasonal variations of signals. Manifestations of these effects in the
Super-Kamiokande and SNO experiments are studied.Comment: 36 pages, LaTeX, includes 14 figures, revised and expande
Constraining Proton Lifetime in SO(10) with Stabilized Doublet-Triplet Splitting
We present a class of realistic unified models based on supersymmetric SO(10)
wherein issues related to natural doublet-triplet (DT) splitting are fully
resolved. Using a minimal set of low dimensional Higgs fields which includes a
single adjoint, we show that the Dimopoulos--Wilzcek mechanism for DT splitting
can be made stable in the presence of all higher order operators without having
pseudo-Goldstone bosons and flat directions. The \mu term of order TeV is found
to be naturally induced. A Z_2-assisted anomalous U(1)_A gauge symmetry plays a
crucial role in achieving these results. The threshold corrections to
alpha_3(M_Z), somewhat surprisingly, are found to be controlled by only a few
effective parameters. This leads to a very predictive scenario for proton
decay. As a novel feature, we find an interesting correlation between the d=6
(p\to e^+\pi^0) and d=5 (p\to \nu-bar K+) decay amplitudes which allows us to
derive a constrained upper limit on the inverse rate of the e^+\pi^0 mode. Our
results show that both modes should be observed with an improvement in the
current sensitivity by about a factor of five to ten.Comment: 21 pages LaTeX, 2 figures, Few explanatory sentences and three new
references added, minor typos corrected
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