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Determination of Electroweak Parameters at the SLC
We present an improved measurement of the left-right cross section asymmetry Alr for Z boson production by e+e- collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC) during the 1994-95 running period. The luminosity-weighted average polarization of the SLC electron beam during this run was measured to be (77.23 +/- 0.52)%. Using a sample of 93,644 hadronic Z decays, we measure the pole asymmetry Alr0 to be 0.1512 +/- 0.0042(stat.) +/- 0.0011(syst.) which is equivalent to an effective weak mixing angle of 0.23100 +/- 0.00054(stat.) +/- 0.00014(syst.). We also present a preliminary direct measurement of the Z-lepton coupling asymmetries A_e,A_mu, and A_tau extracted from the differential cross section observed in leptonic Z decays. We combine these results with our previous Alr measurement to obtain a combined determination of the weak mixing angle of 0.23061 +/- 0.00047
The Leadership Development Experiences of Church Denomination Executives
Leadership development through experiences is thought to be one of the most effective approaches in the development of leaders. Exploring the types of experiences of executive church leaders adds to the body of leadership development research focused on leadership lessons, and reveals the contexts through which these experiences were formed. this study applies a phenomenological approach to capture the essence of the leadership development experiences of several bishops within a single African American denomination. Six major themes emerged as important elements of their collective experience. these findings suggest that leadership development experiences for executive church leaders should include ministry venture creation, the use of relevant and real cases, and mentoring relationships
Langley Mach 4 scramjet test facility
An engine test facility was constructed at the NASA Langley Research Center in support of a supersonic combustion ramjet (scramjet) technology development program. Hydrogen combustion in air with oxygen replenishment provides simulated air at Mach 4 flight velocity, pressure, and true total temperature for an altitude range from 57,000 to 86,000 feet. A facility nozzle with a 13 in square exit produces a Mach 3.5 free jet flow for engine propulsion tests. The facility is described and calibration results are presented which demonstrate the suitability of the test flow for conducting scramjet engine research
Beam energy measurement at linear colliders using spin precession
Linear collider designs foresee some bends of about 5-10 mrad. The spin
precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it
changes proportional to the energy. Measurement of the spin direction using
Compton scattering of laser light on electrons before and after the bend allows
determining the beam energy with an accuracy about of 10^{-5}. In this paper
the principle of the method, the procedure of the measurement and possible
errors are discussed. Some remarks about importance of plasma focusing effects
in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal
publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on
Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept
2-6, 200
Astronomical Site Ranking Based on Tropospheric Wind Statistics
We present comprehensive and reliable statistics of high altitude wind speeds
and the tropospheric flows at the location of five important astronomical
observatories. Statistical analysis exclusively of high altitude winds point to
La Palma as the most suitable site for adaptive optics, with a mean value of
22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the
ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have
found a clear annual periodicity of high altitude winds for the five sites in
study. We have also explored the connection of high to low altitude atmospheric
winds as a first approach of the linear relationship between the average
velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001).
We may conclude that high and low altitude winds show good linear relationships
at the five selected sites. The highest correlation coefficients correspond to
Paranal and San Pedro Martir, while La Palma and La Silla show similar high to
low altitude wind connection. Mauna Kea shows the smallest degree of
correlation, which suggests a weaker linear relationship. Our results support
the idea of high altitude winds as a parameter for rank astronomical sites in
terms of their suitability for adaptive optics, although we have no evidence
for adopting the same linear coefficient at different sites. The final value of
this linear coefficient at a particular site could drastically change the
interpretation of high altitude wind speeds as a direct parameter for site
characterization.Comment: 18 pages, 5 figures. Accepted in MNRA
Performance of BPM Electronics for the LEP Spectrometer
At the LEP e+/e- collider at CERN, Geneva, a Spectrometer is used to determine the beam energy with a relative accuracy of 10-4. The Spectrometer measures the change in bending angle in a well-characterised dipole magnet as LEP is ramped. The beam trajectory is obtained using three beam position monitors (BPMs) on each side of the magnet. The error on each BPM measurement should not exceed 1 micron if the desired accuracy on the bending angle is to be reached. The BPMs used consist of an aluminium block with an elliptical aperture and four capacitive button pickup electrodes. The button signals are fed to customised electronics supplied by Bergoz. The electronics use time multiplexing of individual button signals through a single processing chain to optimise for long-term stability. We report on our experience of the performance of these electronics, describing measurements made with test signals and with beam. We have implemented a beam-based calibration procedure and have monitored the reproducibility of the measurements obtained over time. Measurements show that a relative accuracy better than 300 nm is achievable over a period of 1 hr
Contribution to the modeling of solar spicules
Solar limb and disc spicule quasi- periodic motions have been reported for a
long time, strongly suggesting that they are oscillating. In order to clear up
the origin and possibly explain some solar limb and disc spicule quasi-periodic
recurrences produced by overlapping effects, we present a simulation model
assuming quasi- random positions of spicules. We also allow a set number of
spicules with different physical properties (such as: height, lifetime and tilt
angle as shown by an individual spicule) occurring randomly.
Results of simulations made with three different spatial resolutions of the
corresponding frames and also for different number density of spicules, are
analyzed. The wavelet time/frequency method is used to obtain the exact period
of spicule visibility. Results are compared with observations of the
chromosphere from i/ the Transition Region and Coronal Explorer (TRACE)
filtergrams taken at 1600 angstrom, ii/ the Solar Optical Telescope (SOT) of
Hinode taken in the Ca II H-line and iii/ the Sac-Peak Dunn's VTT taken in
H{\alpha} line. Our results suggest the need to be cautious when interpreting
apparent oscillations seen in spicule image sequences when overlapping is
present, i.e.; when the spatial resolution is not enough to resolve individual
components of spicules.Comment: 20 pages, 7 figures, 1 tabl
ILRS Website Update
The ILRS website, http://ilrs.gsfc.nasa.gov, is the central source of information for all aspects of the service. The website provides information on the organization and operation of the ILRS and descriptions of ILRS components data, and products. Furthermore, the website provides an entry point to the archive of these data products available through the data centers. Links are provided to extensive information on the ILRS network stations including performance assesments and data quality evaluations. Descriptions of suported satellite missions (current, future, and past) are provided to aid in station acquisition and data analysis. The website was reently redesigned. Content was reviewed during the update process, ensuring information is current and useful. This poster will provide specific examples of key sections, applicaitons, and webpages
Determination of the Accuracy of Wire Position Sensors
An energy spectrometer has been installed in the LEP accelerator to determine the beam energy with a relative accuracy of 10-4. A precisely calibrated bending magnet is flanked by 6 beam position monitors (BPM). The beam energy is determined by measuring the deflection angle of the LEP beams and the integrated bending field. An accuracy of less than 10-6 m on the beam position is necessary to reach the desired accuracy on the LEP beam energy. Capacitive wire positioning sensors are used to determine the relative mounting stability of each BPM and to calibrate the beam position monitors. Two-dimensional sensors are attached to each side of every BPM support and provide a position measurement with respect to two stretched wires mounted on either side of the LEP beam pipe. The fixing points of each wire are monitored by additional reference sensors. The position information is digitised via a multiplexed high accuracy digital voltmeter and read out continuously during LEP operations. Wire position sensor accuracy was tested in the laboratory with a laser interferometer, while relative accuracy tests are performed in the LEP environment. Systematic effects of synchrotron radiation on the wire position sensor performance were studied
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