7,161 research outputs found
Dynamically Warped Theory Space and Collective Supersymmetry Breaking
We study deconstructed gauge theories in which a warp factor emerges
dynamically and naturally. We present nonsupersymmetric models in which the
potential for the link fields has translational invariance, broken only by
boundary effects that trigger an exponential profile of vacuum expectation
values. The spectrum of physical states deviates exponentially from that of the
continuum for large masses; we discuss the effects of such exponential towers
on gauge coupling unification. We also present a supersymmetric example in
which a warp factor is driven by Fayet-Iliopoulos terms. The model is peculiar
in that it possesses a global supersymmetry that remains unbroken despite
nonvanishing D-terms. Inclusion of gravity and/or additional messenger fields
leads to the collective breaking of supersymmetry and to unusual phenomenology.Comment: 28 pages LaTeX, JHEP format, 7 eps figures (v2: reference added
W physics at the ILC with polarized beams as a probe of the Littlest Higgs Model
We study the possibility of using W pair production and leptonic decay of one
of the W's at the ILC with polarized beams as a probe of the Littlest Higgs
Model. We consider cross-sections, polarization fractions of the W's, leptonic
decay energy and angular distributions, and left-right polarization asymmetry
as probes of the model. With parameter values allowed by present experimental
constraints detectable effects on these observables at typical ILC energies of
500 GeV and 800 GeV will be present. Beam polarization is further found to
enhance the sensitivity.Comment: 17 pages, plain latex, 6 figures, replaced with version accepted by
JHEP, typographical errors removed, notation and references improved, new
references added, explanation added in appendix regarding beam polarization
dependenc
The correction of the littlest Higgs model to the Higgs production process in collisions
The littlest Higgs model is the most economical one among various little
Higgs models. In the context of the littlest Higgs(LH) model, we study the
process and calculate the contributions of the
LH model to the cross section of this process. The results show that, in most
of parameter spaces preferred by the electroweak precision data, the value of
the relative correction is larger than 10%. Such correction to the process
is large enough to be detected via
collisions in the future high energy linear collider()
experiment with the c.m energy =500 GeV and a yearly integrated
luminosity , which will give an ideal way to test the
model.Comment: 13 pages, 4 figure
CDF Multi-Muon Events and Singlet Extensions of the MSSM
We discuss a generalization of the minimal supersymmetric extension of the
Standard Model in the form of three additional singlet superfields, which would
explain the essential features of the CDF multi-muon events presented recently:
a large production cross section of ~ 100 pb originates from the production of
a CP-odd scalar A with a mass in the 70 - 80 GeV range and a large value of
tan(beta) ~ 40. The CP-odd scalar A decays dominantly into CP-odd and CP-even
scalars a_1 and h_1, which generate decay cascades h_1 -> 2 h_2 -> 4 a_2 -> 8
tau-leptons, and a_1 -> h_1 a_2 with h_1 decaying as above. The decay a_2 ->
tau+ tau- is slow, leading to a lifetime of O(20) ps. The phenomenology of the
model differs from similar scenarios presented before in that one of the two
cascades leads to 10 instead of 8 tau-leptons, and additional production
processes like associate A production with b b-bar pairs are relevant.Comment: 10 pages, comments on the required total cross section added, to
appear in MPL
Pseudo-axions in Little Higgs models
Little Higgs models have an enlarged global symmetry which makes the Higgs
boson a pseudo-Goldstone boson. This symmetry typically contains spontaneously
broken U(1) subgroups which provide light electroweak-singlet pseudoscalars.
Unless such particles are absorbed as the longitudinal component of
states, they appear as pseudoscalars in the physical spectrum at the
electroweak scale. We outline their significant impact on Little Higgs
phenomenology and analyze a few possible signatures at the LHC and other future
colliders in detail. In particular, their presence significantly affects the
physics of the new heavy quark states predicted in Little Higgs models, and
inclusive production at LHC may yield impressive diphoton resonances.Comment: 28 pages, 9 figs., accepted to PRD; footnote added, typos correcte
Transverse spectral functions and Dzyaloshinskii-Moriya interactions in XXZ spin chains
Recently much progress has been made in applying field theory methods, first
developed to study X-ray edge singularities, to interacting one dimensional
systems in order to include band curvature effects and study edge singularities
at arbitrary momentum. Finding experimental confirmations of this theory
remains an open challenge. Here we point out that spin chains with uniform
Dzyaloshinskii-Moriya (DM) interactions provide an opportunity to test these
theories since these interactions may be exactly eliminated by a gauge
transformation which shifts the momentum. However, this requires an extension
of these X-ray edge methods to the transverse spectral function of the xxz spin
chain in a magnetic field, which we provide
Pseudonatural Inflation
We study how to obtain a sufficiently flat inflaton potential that is natural
from the particle physics point of view. Supersymmetry, which is broken during
inflation, cannot protect the potential against non-renormalizable operators
violating slow-roll. We are therefore led to consider models based on
non-linearly realized symmetries. The basic scenario with a single
four-dimensional pseudo Nambu Goldstone boson requires the spontaneous breaking
scale to be above the Planck scale, which is beyond the range of validity of
the field theory description, so that quantum gravity corrections are not under
control. A nice way to obtain consistent models with large field values is to
consider simple extensions in extra-dimensional setups. We also consider the
minimal structures necessary to obtain purely four-dimensional models with
spontaneous breaking scale below M_P; we show that they require an approximate
symmetry that is supplemented by either the little-Higgs mechanism or
supersymmetry to give trustworthy scenarios.Comment: 30 pages, 2 figures. v2: minor changes, ref. added, accepted for JCA
Discrete Gravitational Dimensions
We study the physics of a single discrete gravitational extra dimension using
the effective field theory for massive gravitons. We first consider a minimal
discretization with 4D gravitons on the sites and nearest neighbor hopping
terms. At the linear level, 5D continuum physics is recovered correctly, but at
the non-linear level the theory becomes highly non-local in the discrete
dimension. There is a peculiar UV/IR connection, where the scale of strong
interactions at high energies is related to the radius of the dimension. These
new effects formally vanish in the limit of zero lattice spacing, but do not do
so quickly enough to reproduce the continuum physics consistently in an
effective field theory up to the 5D Planck scale. Nevertheless, this model does
make sense as an effective theory up to energies parametrically higher than the
compactification scale. In order to have a discrete theory that appears local
in the continuum limit, the lattice action must have interactions between
distant sites. We speculate on the relevance of these observations to the
construction of finite discrete theories of gravity in four dimensions.Comment: 5 pages, 4 diagrams. Important typos in some equations corrected;
conclusion s unchange
Renal functions in pediatric patients with beta-thalassemia major: relation to chelation therapy: original prospective study
<p>Abstract</p> <p>Background</p> <p>In β-thalassemia, profound anemia and severe hemosiderosis cause functional and physiological abnormalities in various organ systems. In recent years, there have been few published studies mainly in adult demonstrating renal involvement in β-thalassemia. This prospective study was aimed to investigate renal involvement in pediatric patients with transfusion dependant beta-thalassemia major (TD-βTM), using both conventional and early markers of glomerular and tubular dysfunctions, and to correlate findings to oxidative stress and iron chelation therapy.</p> <p>Methods</p> <p>Sixty-nine TD-βTM patients (aged 1-16 years) and 15 healthy controls (aged 3-14 years) were enrolled in this study. Based on receiving chelation therapy (deferoxamine, DFO), patients were divided into two groups: group [I] with chelation (n = 34) and group [II] without chelation (n = 35). Levels of creatinine (Cr), calcium (Ca), inorganic phosphorus (PO<sub>4</sub>), uric acid (UA) and albumin were measured by spectrophotometer. Serum (S) levels of cystatin-C (S<sub>CysC</sub>) and total antioxidant capacity (S<sub>TAC</sub>) and urinary (U) levels of β<sub>2</sub>-microglobulin (U<sub>β2MG</sub>) were measured by immunosorbent assay (ELISA). Urinary N-acetyl-beta-D-glucosaminidase (U<sub>NAG</sub>) activity and malondialdehyde (U<sub>MDA</sub>) were measured by chemical methods. Estimated glomerular filtration rate (eGFR) was determined from serum creatinine.</p> <p>Results</p> <p>In patient with and without chelation, glomerular [elevated S<sub>CysC</sub>, S<sub>Cr</sub>, U<sub>albumin</sub>/Cr and diminished eGFR]; and tubular dysfunctions [elevated S<sub>UA</sub>, S<sub>PO4</sub>, U<sub>NAG</sub>/Cr, U<sub>β2MG</sub>/Cr] and oxidative stress marker disturbances [diminished S<sub>TAC </sub>and elevated U<sub>MDA</sub>/Cr] were reported than controls. In patients with chelation, S<sub>CysC </sub>was significantly higher while, S<sub>TAC </sub>was significantly lower than those without chelation. In all patients, S<sub>CysC </sub>showed significant positive correlation with S<sub>Cr </sub>and negative correlation with eGFR; S<sub>TAC </sub>showed significant positive correlation with eGFR and negative correlation with S<sub>Cys</sub>C, S<sub>Cr</sub>, U<sub>NAG</sub>/Cr; U<sub>MDA</sub>/Cr showed significant positive correlation with U<sub>albumin</sub>/Cr, U<sub>β2MG</sub>/Cr, U<sub>NAG</sub>/Cr.</p> <p>Conclusions</p> <p>Our data confirm high frequency of glomerular and tubular dysfunctions in TD-βTM pediatric patients which could be attributed to oxidative stress and DFO therapy.</p
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