5,947 research outputs found
Multifacility location problems on a sphere
A unified approach to multisource location problems on a sphere is presented. Euclidean, squared Euclidean and the great circle distances are considered. An algorithm is formulated and its convergence properties are investigated
PB.14. An analysis of subtle alterations in reading pattern with the introduction of digital mammography screening: South East Scotland Breast Screening Programme
Lepton Flavor Violation and the Origin of the Seesaw Mechanism
The right--handed neutrino mass matrix that is central to the understanding
of small neutrino masses via the seesaw mechanism can arise either (i) from
renormalizable operators or (ii) from nonrenormalizable or super-renormalizable
operators, depending on the symmetries and the Higgs content of the theory
beyond the Standard Model. In this paper, we study lepton flavor violating
(LFV) effects in the first class of seesaw models wherein the \nu_R Majorana
masses arise from renormalizable Yukawa couplings involving a B-L = 2 Higgs
field. We present detailed predictions for \tau -> \mu + \gamma and \mu -> e +
\gamma branching ratios in these models taking the current neutrino oscillation
data into account. Focusing on minimal supergravity models, we find that for a
large range of MSSM parameters suggested by the relic abundance of neutralino
dark matter and that is consistent with Higgs boson mass and other constraints,
these radiative decays are in the range accessible to planned experiments. We
compare these predictions with lepton flavor violation in the second class of
models arising entirely from the Dirac Yukawa couplings. We study the
dependence of the ratio r \equiv B(\mu -> e+\gamma)/B(\tau ->\mu +\gamma) on
the MSSM parameters and show that measurement of r can provide crucial insight
into the origin of the seesaw mechanism.Comment: 20 pages, Revtex, 7 figure
Suppressing dimension-5 operators in general SU(5) models
We discuss dimension-5 operators in supersymmetric models containing extra
hypercharge 1/3 color-triplets. We derive a general formula relating
dimension-5 operator to the color-triplet mass matrix. We show that certain
zeros in the triplet mass-matrix together with some triplet coupling selection
rules can lead to elimination of dimension-5 operators. In particular we focus
on SU(5) models and show that (a) Dimension-5 operators can be eliminated in
the standard SU(5) model by the introduction of an extra pair of 5+5b Higgses
with specific couplings (b) Flipped SU(5) models with extra 10+10b Higgses are
free of dimension-5 operators (c) Flipped SU(5) models with extra 5+5b and/or
extra 10+10b Higgses can be made free of dimension-5 operators for a textured
form of the triplet mass-matrix accompanied by constraints on the 5-plet
couplings to matter. Our analysis is motivated by the recently put forward
M-theory phenomenological framework that requires a strong string coupling and
reintroduces the problem of eliminating dimension-5 operators.Comment: 10 pages, Latex2e, minor changes, references adde
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
A RAPID RP-HPLC METHOD DEVELOPMENT AND VALIDATION FOR THE QUANTITATIVE ESTIMATION RIBAVIRIN IN TABLETS
Objective: To develop an accurate, precise and linear Reverse Phase High Performance Liquid Chromatography (RP-HPLC) method and validate as per ICH guidelines for the quantitative estimation of Ribavirin (200mg) in tablets.Methods: The optimized method uses a reverse phase column, Enable Make KromasilC18 (250 X 4.6 mm; 5μ), a mobile phase of phosphate buffer (pH 4.2): acetonitrile in the proportion of 85:15 v/v, flow rate of 1.0 ml/min and a detection wavelength of 215 nm using a PDA detector.Results: The developed method resulted in Ribavirin eluting at 2.606 min. Ribavirin exhibited linear in the range 25-150μg/ml. The precision is exemplified by the relative standard deviation of 0.4%. Percentage Mean recovery was found to be in the range of 98â€102, during accuracy studies. The limit of detection (LOD) and limit of quantitiation (LOQ) was found to be 0.24ng/ml and 0.73ng/ml respectively.Conclusion: An accurate, precise and linear RP-HPLC method was developed and validated for the quantitative estimation of Ribavirin in VIRAZIDE (200mg) tablets as per ICH guidelines and hence it can be used for the routine analysis in various pharmaceutical industries.Â
Higgs-Mediated tau -> 3 mu in the Supersymmetric Seesaw Model
Recent observations of neutrino oscillations imply non-zero neutrino masses
and flavor violation in the lepton sector, most economically explained by the
seesaw mechanism. Within the context of supersymmetry, lepton flavor violation
(LFV) among the neutrinos can be communicated by renormalization group flow to
the sleptons and from there to the charged leptons. We show that LFV can appear
in the couplings of the neutral Higgs bosons, an effect that is strongly
enhanced at large tan(beta). In particular, we calculate the branching fraction
for tau -> 3 mu and mu -> 3 e mediated by Higgs and find that they can be as
large as 10^{-7} and 5x10^{-14} respectively. These modes, along with B^0 -> mu
mu, can provide important evidence for supersymmetry before direct discovery of
supersymmetric partners occurs. Along with tau -> mu gamma and mu -> e gamma,
they can also provide key insights into the form of the neutrino Yukawa mass
matrix.Comment: 9 pages LaTeX, 2 figures. Added a discussion of mu -> 3e and its
ramifications for probing neutrino mass matrix. Also added references, fixed
typos, and made one notational chang
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
Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data
A new analysis of the hadronic peak cross section at LEP 1 implies a small
amount of missing invisible width in Z decays, while the effective weak charge
in atomic parity violation has been determined recently to 0.6% accuracy,
indicating a significantly negative S parameter. As a consequence of these two
deviations, the data are described well if the presence of an additional Z'
boson, such as predicted in Grand Unified Theories, is assumed. Moreover, the
data are now rich enough to study an arbitrary extra Z' boson and to determine
its couplings in a model independent way. An excellent best fit to the data is
obtained in this case, suggesting the possibility of a family non-universal Z'
with properties similar to ones predicted in a class of superstring theories.Comment: 5 pages of ReVTeX, 2 figure
Supersymmetric SO(10) Simplified
In the context of supersymmetric grand unified models, it is shown
that the gauge symmetry breaking as well as a natural doublet--triplet
splitting can be achieved with a minimal Higgs system consisting of a single
adjoint and a pair of vector and spinor multiplets. Such a Higgs spectrum has
been shown to arise in the free fermionic formulation of superstrings. Since
the symmetry breaking mechanism relies on non--renormalizable operators, some
of the Higgs particles of the model turn out to have masses somewhat below the
GUT scale. As a consequence, the unification scale is raised to about and sin is predicted to be slightly larger than the
minimal SUSY-- value. Including threshold uncertainties, which turn out
to be surprisingly small in the model, we show that sin prediction
is consistent with experiments.Comment: 23 pages, BA-94-4
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