97 research outputs found
Electroweak Precision Constraints on the Littlest Higgs Model with T Parity
We compute the leading corrections to the properties of W and Z bosons
induced at the one-loop level in the SU(5)/SO(5) Littlest Higgs model with T
parity, and perform a global fit to precision electroweak data to determine the
constraints on the model parameters. We find that a large part of the model
parameter space is consistent with data. Values of the symmetry breaking scale
as low as 500 GeV are allowed, indicating that no significant fine tuning in
the Higgs potential is required. We identify a region within the allowed
parameter space in which the lightest T-odd particle, the partner of the
hypercharge gauge boson, has the correct relic abundance to play the role of
dark matter. In addition, we find that a consistent fit to data can be obtained
for large values of the Higgs mass, up to 800 GeV, due to the possibility of a
partial cancellation between the contributions to the T parameter from Higgs
loops and new physics.Comment: 23 pages, 9 figures. Minor correction
Higher dimensional supersymmetry in 4D superspace
We present an explicit formulation of supersymmetric Yang-Mills theories from
\D= 5 to 10 dimensions in the familiar \N=1,\D=4 superspace. This provides
the rules for globally supersymmetric model building with extra dimensions and
in particular allows us to simply write down SUSY preserving
interactions between bulk fields and fields localized on branes. We present a
few applications of the formalism by way of illustration, including
supersymmetric ``shining'' of bulk fields, orbifolds and localization of chiral
fermions, anomaly inflow and super-Chern-Simons theories.Comment: Typos corrected. Added reference to early work by Marcus, Sagnotti
and Siegel and a term to the non-Abelian Lagrangian for D>5 formally needed
for gauge invariance. The results however remain unchange
What Precision Electroweak Physics Says About the SU(6)/Sp(6) Little Higgs
We study precision electroweak constraints on the close cousin of the
Littlest Higgs, the SU(6)/Sp(6) model. We identify a near-oblique limit in
which the heavy W' and B' decouple from the light fermions, and then calculate
oblique corrections, including one-loop contributions from the extended top
sector and the two Higgs doublets. We find regions of parameter space that give
acceptably small precision electroweak corrections and only mild fine tuning in
the Higgs potential, and also find that the mass of the lightest Higgs boson is
relatively unconstrained by precision electroweak data. The fermions from the
extended top sector can be as light as 1 TeV, and the W' can be as light as 1.8
TeV. We include an independent breaking scale for the B', which can still have
a mass as low as a few hundred GeV.Comment: 52 pages, 16 figure
Fermions on an Interval: Quark and Lepton Masses without a Higgs
We consider fermions on an extra dimensional interval. We find the boundary
conditions at the ends of the interval that are consistent with the variational
principle, and explain which ones arise in various physical circumstances. We
apply these results to higgsless models of electroweak symmetry breaking, where
electroweak symmetry is not broken by a scalar vacuum expectation value, but
rather by the boundary conditions of the gauge fields. We show that it is
possible to find a set of boundary conditions for bulk fermions that would give
a realistic fermion mass spectrum without the presence of a Higgs scalar, and
present some sample fermion mass spectra for the standard model quarks and
leptons as well as their resonances.Comment: LaTeX, 36 pages, 5 figure
Hepatic abnormalities in patients with chronic granulomatous disease
Chronic granulomatous disease (CGD) is a rare congenital disorder characterized
by repeated bacterial and fungal infections. Aside from a high incidence of liver
abscess, little is known about hepatic involvement in CGD. The aim of this study
was to describe the spectrum of liver abnormalities seen in CGD. The charts of
194 patients with CGD followed at the NIH were reviewed, with a focus on liver
abnormalities. Liver enzyme elevations occurred on at least one occasion in 73%
of patients during a mean of 8.9 years of follow-up. ALT elevations were
generally transient. Although transient alkaline phosphatase (ALP) elevations
were also common, persistent ALP elevations lasting up to 17.6 years were seen in
25% of patients. Liver abscess occurred in 35% of patients. Drug-induced
hepatotoxicity was documented in 15% of patients but likely occurred more
frequently. Hepatomegaly was found in 34% and splenomegaly in 56% of patients.
Liver histology showed granulomata in 75% and lobular hepatitis in 90% of
specimens. Venopathy of the portal vein was common (80%) and associated with
splenomegaly. Venopathy of the central vein was also common (63%) and was
associated with the number of abscess episodes. Nodular regenerative hyperplasia
(NRH) was seen in 9 patients, including 6 of 12 autopsy specimens. CONCLUSION:
Liver enzyme abnormalities occur frequently in patients with CGD. In addition to
liver abscesses and granulomata, drug hepatotoxicity is likely underappreciated.
Vascular lesions such as venopathy and--to a lesser extent--NRH are common. The
cause and clinical consequences of venopathy await prospective evaluation
FORUM: Toward a Phenomenology of Interviews
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43940/1/11422_2005_Article_9001.pd
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