323 research outputs found
On Neutrino Masses and Mixings from Extra Dimensions
In the framework of a Kaluza-Klein type theory with the Standard Model fields
localized on a 4-dimensional section while gravity propagates in a full
-dimensional space-time, we examine a mechanism of naturally small
neutrino mass generation through couplings of Standard Model singlet fermion(s)
living also in the full space-time. A numerical studies is carried out on the
charged current universality constraint from the ratio of pion decay partial
widths. The bounds obtained on the fundamental mass scale could be stringent.Comment: 16 pages latex, no figure; small modifications in discussions;
version to appear in Phys.Lett.
The Generic Supersymmetric Standard Model as the Complete Theory of Supersymmetry without R-parity
The generic supersymmetric standard model is a model built from a
supersymmetrized standard model field spectrum the gauge symmetries only. The
popular minimal supersymmetric standard model differs from the generic version
in having R-parity imposed by hand. We review an efficient formulation of the
model in which all the admissible R-parity violating terms are incorporated
without bias. The model gives many new interesting R-parity violating
phenomenological features only started to be studied recently. Some of our
recent results will be discussed, including newly identified 1-loop
contributions to neutrino masses and electric dipole moments of neutron and
electron. This is related to the largely overlooked R-parity violating
contributions to squark and slepton mixings, which we also present in detail.Comment: 10 pages latex using espcrc2.sty (included) with a latex table and 3
eps- figure files incoporated, typos in a couple of expressions fixe
A Simple Phenomenological Parametrization of Supersymmetry without R-Parity
We present a parametrization of the supersymmetric standard model without
R-parity that permits efficient phenomenological analyses of the full model
without a priori assumptions. Under the parametrization, which is characterized
by a single vacuum expectation value for the scalar components of the Y=-1/2
superfields, the expressions for tree-level mass matrices are quite simple.
They do not involve the trilinear R-parity violating couplings; however, the
bilinear {\mu}_i terms do enter and cannot be set to zero without additional
assumptions. We set up a framework for doing phenomenology and show some
illustrative results for fermion mass matrices and related bounds on
parameters. We find in particular that large values of tan(beta) can suppress
R-parity violating effects, substantially weakening experimental constraints.Comment: LaTeX file plus postscript figure files, 17 pages; minor
typographical changes, to appear in Physics Letters
Could the be substantially different from and in the supersymmetric standard model?
R-parity stands as an ad hoc assumption in the most popular version of the
supersymmetric standard model. More than fifteen years' studies of R-parity
violations have been restricted to various limiting scenarios. We illustrate
how the single-VEV parametrization provides a workable framework to analyze the
phenomenology of the complete theory of supersymmetry without R-parity. In our
comprehensive study of various aspects of the resulting leptonic phenomenology
at tree-level, we find that the physical lepton could actually bear
substantial gaugino and higgsino components, making it very different from the
and the .Comment: 7 pages in postscript. Talk given by O.K. at Tau98, to be published
in the proceedings; reprint number adde
Education and awareness of modern health care amongst aboriginal people: the case of the Jakuns of Peninsular Malaysia
Previous studies have indicated that the resettlement of the Orang Asli communities into areas nearer to towns was
with the intention of improving the health conditions of the aboriginals. Subsequent researches have since focused
on the relation between mainstream orthodox medical approaches and traditional healing practices in search of
improved approaches to advance further the health cause of the aboriginal communities. However, none of these
works have addressed the central question of how the Orang Asli have been adapting themselves to the mainstream
healthcare system while still holding strong beliefs in their traditional medicine. To close the gap this study
examined the readiness and intentions of the Orang Asli in adapting to modern health care approach amidst old
traditional health beliefs and healings practices. A qualitative study based on in-depth interviews and field
observations was carried out at a Jakun village of Kampung Kedaik, Rompin, Pahang involving 12 male and 13
female informants between 18 – 70 years old. Results of the study showed that as the Orang Asli people received
proper education they appeared to think about health differently. Most of the informants preferred modern over
traditional medicine predominantly because of their deteriorating faith in, and relative inaccessibility to traditional
medicine. The findings implied that in this modern day most of the indigenous communities were open to social
change which in this context included modern health care so as to improve their health conditions
Flavor Changing Higgs Decays in Supersymmetry with Minimal Flavor Violation
We study the flavor changing neutral current decays of the MSSM Higgs bosons
into strange and bottom quarks. We focus on a scenario of minimum flavor
violation here, namely only that induced by the CKM matrix. Taking into account
constraint from , as well as experimental
constraints on the MSSM spectrum, we show that the branching ratio of and combined, for being either one of
the CP even Higgs states, can reach the order - for large
, large , and large . The result illustrates the
significance of minimal flavor violation scenario which can induce competitive
branching fraction for flavor changing Higgs decays. This can be compared with
the previous studies where similar branching fraction has been reported, but
with additional sources of flavor violations in squark mass matrices. We also
discuss some basic features of the flavor violating decays in the generic case.Comment: 16 pages on Revtex, with 5 figures from 10 eps files incorporated;
discussion on issues related more precise calculations elaborated;
proof-edited version to appear in Phys. Lett.
Solution to the strong CP problem with gauge-mediated supersymmetry breaking
We demonstrate that a certain class of low scale supersymmetric ``Nelson-Barr'' type models can solve the strong and supersymmetric CP problems while at the same time generating sufficient weak CP violation in the system. In order to prevent one-loop corrections to which violate bounds coming from the neutron electric dipole moment (EDM), one needs a scheme for the soft supersymmetry breaking parameters which can naturally give sufficient squark degeneracies and proportionality of trilinear soft supersymmetry-breaking parameters to Yukawa couplings. We show that a gauge-mediated supersymmetry breaking sector can provide the needed degeneracy and proportionality, though that proves to be a problem for generic Nelson-Barr models. The workable model we consider here has the Nelson-Barr mass texture enforced by a gauge symmetry; one also expects a new U(1) gauge superfield with mass in the TeV range. The resulting model is predictive. We predict a measureable neutron EDM and the existence of extra vector-like quark superfields which can be discovered at the LHC. Because the Cabbibo-Kobayashi-Maskawa matrix is approximately real, the model also predicts a flat unitarity triangle and the absence of substantial CP violation in the system at future factories. We discuss the general issues pertaining to the construction of such a workable model and how they lead to the successful strategy. A detailed renormalization group study is then used to establish the feasibility of the model considered
Effects of Al doping on the structural and electronic properties of Mg(1-x)Al(x)B2
We have studied the structural and electronic properties of Mg(1-x)Al(x)B2
within the Virtual Crystal Approximation (VCA) by means of first-principles
total-energy calculations. Results for the lattice parameters, the electronic
band structure, and the Fermi surface as a function of Al doping for 0<x<0.6
are presented. The ab initio VCA calculations are in excellent agreement with
the experimentally observed change in the lattice parameters of Al doped MgB2.
The calculations show that the Fermi surface associated with holes a the boron
planes collapses gradually with aluminum doping and vanishes for x=0.56. In
addition, an abrupt topological change in the sigma-band Fermi surface was
found for x=0.3. The calculated hole density correlates closely with existing
experimental data for Tc(x), indicating that the observed loss of
superconductivity in Mg(1-x)Al(x)B2 is a result of hole bands filling.Comment: 4 pages (revtex) and 4 figures (postscript
Strong CP and Low-energy Supersymmetry
A spontaneously-broken CP provides an alternative to the KM mechanism for CP
violation with the advantage that the strong CP problem is solved. We consider,
for such a model with a new gauged U(1), the incorporation of low-energy
supersymmetry and find the constraints on alignment and squark degeneracy. The
conclusion is that although the constraints are much less severe
than in other generic schemes with supersymmetry breaking and spontaneous CP
violation, one restriction remains stronger than needed in the MSSM for
suppression of FCNC.Comment: Title changed. Discussions added. Version to appear in Phys. Lett.
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