1,602 research outputs found
Design study of an entry probe spectro-reflectometer
A wind tunnel was built to simulate the rapid movement of an entry probe through the Jupiter atmosphere. Wind speeds range from 1 to 50 meters per second in a closed system. Wind velocity and temperature probes as well as a cryogenically cooled cold finger can be placed in the 6 inch diameter viewing section. The initial testing of the wind tunnel involved running sectional profiles through the observation port of air currents of 0.1 to 3.0 atmosphere. The velocity profile was very uniform throughout the cross section of the experimental port, with the exception of the wall effects. The deposition of cooled volatiles using the wind tunnel was not performed. However, measurements of the deposition of H2O ice on a cryogenically cooled thickness modulator were made under ambient conditions, namely room temperature and pressure. In the Frost Depositon Test Facility, ice deposition was measured at thicknesses of about a half millimeter and frost was produced whose thickness reflectivity could easily be measured by reflectance spectroscopy
The infrared spectrum of carbon suboxide. Part 1 - Region 1-2.5 microns. Part 2 - Region 2-15 microns. Part 3 - Classification of carbon suboxide vibrational bands
Laboratory tests of infrared spectrum of carbon suboxide, to determine presence in Venus and Mars atmosphere
Fluctuations in viscous fingering
Our experiments on viscous (Saffman-Taylor) fingering in Hele-Shaw channels
reveal finger width fluctuations that were not observed in previous
experiments, which had lower aspect ratios and higher capillary numbers Ca.
These fluctuations intermittently narrow the finger from its expected width.
The magnitude of these fluctuations is described by a power law, Ca^{-0.64},
which holds for all aspect ratios studied up to the onset of tip instabilities.
Further, for large aspect ratios, the mean finger width exhibits a maximum as
Ca is decreased instead of the predicted monotonic increase.Comment: Revised introduction, smoothed transitions in paper body, and added a
few additional minor results. (Figures unchanged.) 4 pages, 3 figures.
Submitted to PRE Rapi
Dual-readout Calorimetry
The RD52 Project at CERN is a pure instrumentation experiment whose goal is
to understand the fundamental limitations to hadronic energy resolution, and
other aspects of energy measurement, in high energy calorimeters. We have found
that dual-readout calorimetry provides heretofore unprecedented information
event-by-event for energy resolution, linearity of response, ease and
robustness of calibration, fidelity of data, and particle identification,
including energy lost to binding energy in nuclear break-up. We believe that
hadronic energy resolutions of {\sigma}/E 1 - 2% are within reach for
dual-readout calorimeters, enabling for the first time comparable measurement
preci- sions on electrons, photons, muons, and quarks (jets). We briefly
describe our current progress and near-term future plans. Complete information
on all aspects of our work is available at the RD52 website
http://highenergy.phys.ttu.edu/dream/.Comment: 10 pages, 10 figures, Snowmass White pape
Radiative Corrections to Electron-Proton Scattering
The radiative corrections to elastic electron-proton scattering are analyzed
in a hadronic model including the finite size of the nucleon. For initial
electron energies above 8 GeV and large scattering angles, the proton vertex
correction in this model increases by at least two percent the overall factor
by which the one-photon exchange (Rosenbluth) cross section must be multiplied.
The contribution of soft photon emission is calculated exactly. Comparison is
made with the generally used expressions previously obtained by Mo and Tsai.
Results are presented for some kinematics at high momentum transfer.Comment: 31 pages, 4 figure
Recalculation of Proton Compton Scattering in Perturbative QCD
At very high energy and wide angles, Compton scattering on the proton (gamma
p -> gamma p) is described by perturbative QCD. The perturbative QCD
calculation has been performed several times previously, at leading twist and
at leading order in alpha_s, with mutually inconsistent results, even when the
same light-cone distribution amplitudes have been employed. We have
recalculated the helicity amplitudes for this process, using contour
deformations to evaluate the singular integrals over the light-cone momentum
fractions. We do not obtain complete agreement with any previous result. Our
results are closest to those of the most recent previous computation, differing
significantly for just one of the three independent helicity amplitudes, and
only for backward scattering angles. We present results for the unpolarized
cross section, and for three different polarization asymmetries. We compare the
perturbative QCD predictions for these observables with those of the handbag
and diquark models. In order to reduce uncertainties associated with alpha_s
and the three-quark wave function normalization, we have normalized the Compton
cross section using the proton elastic form factor. The theoretical predictions
for this ratio are about an order of magnitude below existing experimental
data.Comment: Latex, 23 pages, 13 figures. Checked numerical integration one more
way; added results for one more proton distribution amplitude; a few other
minor changes. Version to appear in Phys. Rev.
Microscopic Selection of Fluid Fingering Pattern
We study the issue of the selection of viscous fingering patterns in the
limit of small surface tension. Through detailed simulations of anisotropic
fingering, we demonstrate conclusively that no selection independent of the
small-scale cutoff (macroscopic selection) occurs in this system. Rather, the
small-scale cutoff completely controls the pattern, even on short time scales,
in accord with the theory of microscopic solvability. We demonstrate that
ordered patterns are dynamically selected only for not too small surface
tensions. For extremely small surface tensions, the system exhibits chaotic
behavior and no regular pattern is realized.Comment: 6 pages, 5 figure
Hadron Polarizabilities and Form Factors
This is the summary of the working group on Hadron Polarizabilities and Form
Factors of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997.Comment: 21 pages LaTeX2e, uses epsf, 9 fig
New empirical fits to the proton electromagnetic form factors
Recent measurements of the ratio of the elastic electromagnetic form factors
of the proton, G_Ep/G_Mp, using the polarization transfer technique at
Jefferson Lab show that this ratio decreases dramatically with increasing Q^2,
in contradiction to previous measurements using the Rosenbluth separation
technique. Using this new high quality data as a constraint, we have reanalyzed
most of the world e-p elastic cross section data. In this paper, we present a
new empirical fit to the reanalyzed data for the proton elastic magnetic form
factor in the region 0 < Q^2 < 30 GeV^2. As well, we present an empirical fit
to the proton electromagnetic form factor ratio, G_Ep/G_Mp, which is valid in
the region 0.1 < Q^2 < 6 GeV^2
Octet-Baryon Form Factors in the Diquark Model
We present an alternative parameterization of the quark-diquark model of
baryons which particularly takes care of the most recent proton electric
form-factor data from the E136 experiment at SLAC. In addition to
electromagnetic form factors of the nucleon, for which good agreement with data
is achieved, we discuss the weak axial vector form factor of the nucleon as
well as electromagnetic form factors of and hyperons.
Technical advance in calculating the pertinent analytic expressions within
perturbative quantum chromodynamics is gained by formulating the wave function
of the quark-diquark system in a covariant way. Finally, we also comment on the
influence of Sudakov corrections within the scope of the diquark model.Comment: 16 pages, WU-B 93-07, latex, uuencoded postscript files of 7 figures
appended at the end of the latex fil
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