150 research outputs found
SM Kaluza-Klein Excitations and Electroweak Precision Tests
We consider a minimal extension to higher dimensions of the Standard Model,
having one compactified dimension, and we study its experimental tests in terms
of electroweak data. We discuss tests from high-energy data at the -pole,
and low-energy tests, notably from atomic parity violation data. This
measurement combined with neutrino scattering data strongly restricts the
allowed region of the model parameters. Furthermore this region is incompatible
at 95% CL with the restrictions from high-energy experiments. Of course a
global fit to all data is possible but the for degree of
freedom is unpleasantly large.Comment: LaTex, 14 pages, 2 figures. More refs. and one comment about the
validity of our results for any number of extra dimensions adde
Electroweak Radiative Corrections To Polarized M{\o}ller Scattering Asymmetries
One loop electroweak radiative corrections to left-right parity violating
M{\o}ller scattering () asymmetries are presented. They
reduce the standard model (tree level) prediction by 40 \% where the
main shift and uncertainty stem from hadronic vacuum polarization loops. A
similar reduction also occurs for the electron-electron atomic parity violating
interaction. That effect can be attributed to an increase of
by in running from to 0. The
sensitivity of the asymmetry to ``new physics'' is also discussed.Comment: 14 pages, Revtex, postscript file including figures is available at
ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-14/ttp95-14.ps or via WWW at
http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints/ (129.13.102.139
Comparative study of the stability of bimatoprost 0.03% and latanoprost 0.005%: A patient-use study
<p>Abstract</p> <p>Background</p> <p>The stability of ophthalmic preparations in multidose containers is influenced by the preservative as well as the stability of the active ingredient. Unstable drugs may require refrigeration to preserve their active ingredient level and they are more likely to degrade over time, therefore becoming more susceptible to degradation based on patient mishandling. The purpose of this study was to determine the degree of molecular degradation that occurs in bimatoprost and latanoprost in a patient-use setting.</p> <p>Methods</p> <p>This was an open-label, laboratory evaluation of the relative stability of bimatoprost and latanoprost. Patients presently using bimatoprost (n = 31) or latanoprost (n = 34) were identified at 2 clinical sites in Brazil. Patients were instructed to use and store their drops as usual and return all used medication bottles between day 28 and day 34 after opening.</p> <p>Results</p> <p>Bimatoprost demonstrated no degradation, but latanoprost degraded at various levels. The mean age of bimatoprost was 43.0 ± 3.4 days and the mean age of latanoprost was 43.9 ± 2.8 days (P = .072). The mean percentage of labeled concentration was 103.7% in the bimatoprost bottles and 88.1% in the latanoprost bottles (P < 001).</p> <p>Conclusion</p> <p>This study showed that bimatoprost maintained â„100% concentration throughout the study period while latanoprost did not.</p
The FourierâKelvin Stellar Interferometer: A Concept for a Practical Interferometric Mission for Discovering and Investigating Extrasolar Giant Planets
The FourierâKelvin Stellar Interferometer (FKSI) is a mission concept for a nulling interferometer for the nearâtoâmidâinfrared spectral region (3 â 8 ÎŒm). FKSI is conceived as a scientific and technological precursor to TPF. The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will answer key questions about extrasolar planets:âą What are the characteristics of the known extrasolar giant planets?âą What are the characteristics of the extrasolar zodiacal clouds around nearby stars?âą Are there giant planets around classes of stars other than those already studied?We present preliminary results of a detailed design study of the FKSI. Using a nulling interferometer configuration, the optical system consists of two 0.5 m telescopes on a 12.5 m boom feeding a MachâZender beam combiner with a fiber wavefront error reducer to produce a 0.01% null of the central starlight. With this system, planets around nearby stars can be detected and characterized using a combination of spectral and spatial resolution. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87917/2/297_1.pd
Atomic Parity Violation and Precision Electroweak Physics - An Updated Analysis
A new analysis of parity violation in atomic cesium has led to the improved
value of the weak charge, . The implications
of this result for constraining the Peskin-Takeuchi parameters S and T and for
guiding searches for new Z bosons are discussed.Comment: 8 pages, LaTeX, 3 figures, Submitted to Physical Review D. Updated
experimental inputs and references; clarification of notatio
Atomic parity nonconservation and neutron radii in cesium isotopes
The interpretation of future precise experiments on atomic parity violation
in terms of parameters of the Standard Model could be hampered by uncertainties
in the atomic and nuclear structure. While the former can be overcome by
measurement in a series of isotopes, the nuclear structure requires knowledge
of the neutron density. We use the nuclear Hartree-Fock method, which includes
deformation effects, to calculate the proton and neutron densities in
{125}Cs-{139}Cs. We argue that the good agreement with the experimental charge
radii, binding energies, and ground state spins signifies that the
phenomenological nuclear force and the method of calculation that we use is
adequate. Based on this agreement, and on calculations involving different
effective interactions, we estimate the uncertainties in the differences of the
neutron radii delta_{N,N'} and conclude that they cause uncertainties in
the ratio of weak charges, the quantities determined in the atomic parity
nonconservation experiments, of less than 10^{-3}. Such an uncertainty is
smaller than the anticipated experimental error.Comment: 24 pages (RevTeX) 4 figures (Postscript/uuencoded compressed) Caltech
Preprint No. MAP-153 (March 1993
The Muonium Atom as a Probe of Physics beyond the Standard Model
The observed interactions between particles are not fully explained in the
successful theoretical description of the standard model to date. Due to the
close confinement of the bound state muonium () can be used as
an ideal probe of quantum electrodynamics and weak interaction and also for a
search for additional interactions between leptons. Of special interest is the
lepton number violating process of sponteanous conversion of muonium to
antimuonium.Comment: 15 pages,6 figure
Contact Interactions Involving Right-handed Neutrinos and SN1987A
We consider lepton-quark contact interactions in models with right-handed
neutrinos, and find that observational data from SN1987A restricts the scale of
such interactions to be at least TeV.Comment: 7 pages, latex, no figures. Minor corrections to match final version
to appear in Phys. Rev.
Atomic Parity Nonconservation: Electroweak Parameters and Nuclear Structure
There have been suggestions to measure atomic parity nonconservation (PNC)
along an isotopic chain, by taking ratios of observables in order to cancel
complicated atomic structure effects. Precise atomic PNC measurements could
make a significant contribution to tests of the Standard Model at the level of
one loop radiative corrections. However, the results also depend upon certain
features of nuclear structure, such as the spatial distribution of neutrons in
the nucleus. To examine the sensitivity to nuclear structure, we consider the
case of Pb isotopes using various recent relativistic and non-relativistic
nuclear model calculations. Contributions from nucleon internal weak structure
are included, but found to be fairly negligible. The spread among present
models in predicted sizes of nuclear structure effects may preclude using Pb
isotope ratios to test the Standard Model at better than a one percent level,
unless there are adequate independent tests of the nuclear models by various
alternative strong and electroweak nuclear probes. On the other hand,
sufficiently accurate atomic PNC experiments would provide a unique method to
measure neutron distributions in heavy nuclei.Comment: 44 pages, INT Preprint DOE/ER/40561-050-INT92-00-1
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