19,523 research outputs found
Electric arc device for heating gases Patent
Electric arc device for minimizing electrode ablation and heating gases to supersonic or hypersonic wind tunnel temperature
Resonance Region Structure Functions and Parity Violating Deep Inelastic Scattering
The primary motive of parity violating deep inelastic scattering experiments
has been to test the standard model, particularly the axial couplings to the
quarks, in the scaling region. The measurements can also test for the validity
of models for the off-diagonal structure functions in the resonance region. The off-diagonal structure functions are
important for the accurate calculation of the -box correction to the
weak charge of the proton. Currently, with no data to determine
directly, models are constructed by modifying
existing fits to electromagnetic data. We present the asymmetry value for
deuteron and proton target predicted by several different models, and demonstrate that there are notable disagreements.Comment: 6 pages, 3 figures. New version contains additional descriptions of
competing structure function model
New Physics and the Proton Radius Problem
Background: The recent disagreement between the proton charge radius
extracted from Lamb shift measurements of muonic and electronic hydrogen
invites speculation that new physics may be to blame. Several proposals have
been made for new particles that account for both the Lamb shift and the muon
anomalous moment discrepancies. Purpose: We explore the possibility that new
particles' couplings to the muon can be fine-tuned to account for all
experimental constraints. Method: We consider two fine-tuned models, the first
involving new particles with scalar and pseudoscalar couplings, and the second
involving new particles with vector and axial couplings. The couplings are
constrained by the Lamb shift and muon magnetic moments measurements while mass
constraints are obtained by kaon decay rate data. Results: For the
scalar-pseudoscalar model, masses between 100 to 200 MeV are not allowed. For
the vector model, masses below about 200 MeV are not allowed. The strength of
the couplings for both models approach that of electrodynamics for particle
masses of about 2 GeV. Conclusions: New physics with fine tuned couplings may
be entertained as a possible explanation for the Lamb shift discrepancy.Comment: 6 pages, 6 figures, v2 contains revised comment on competing model of
Lamb Shift discrepanc
Gamma-Z box contributions to parity violating elastic e-p scattering
Parity-violating (PV) elastic electron-proton scattering measures Q-weak for
the proton, . To extract from data, all radiative corrections
must be well-known. Recently, disagreement on the gamma-Z box contribution to
has prompted the need for further analysis of this term. Here, we
support one choice of a debated factor, go beyond the previously assumed
equality of electromagnetic and gamma-Z structure functions, and find an
analytic result for one of the gamma-Z box integrals. Our numerical evaluation
of the gamma-Z box is in agreement within errors with previous reports, albeit
somewhat larger in central value, and is within the uncertainty requirements of
current experiments.Comment: 4 pages, 4 figures, v2: reference added, typo fixe
Leading-Log Effects in the Resonance Electroweak Form Factors
We study log corrections to inelastic scattering at high Bjorken x for Q^2
from 1 to 21 GeV^2. At issue is the presence of log corrections, which can be
absent if high x scattering has damped gluon radiation. We find logarithmic
correction of the scaling curve extrapolated to low Q^2 improves the duality
between it and the resonance plus background data in the Delta region,
indicating log corrections exist in the data. However, at W > 2 GeV and high x,
the data shows a (1-x)^3 form. Log corrections in one situation but not in
another can be reconciled by a W- or Q^2- dependent higher twist correction.Comment: 13 pages, report nos. RPI-94-N90 and WM-94-106, revtex, two figures
(available by fax or post
Upgrading of NASA-Ames high-energy hypersonic facilities: A Study
This study reviews facility capabilities of NASA, Ames Research Center to simulate hypersonic flight with particular emphasis on arc heaters. Scaling laws are developed and compared with ARCFLO II calculations and with existing data. The calculations indicate that a 300 MW, 100 atmosphere arc heater is feasible. Recommendations for the arc heater, which will operate at voltages up to 50 kilovolts, and the associated elements needed for a test facility are included
Quantum Monte Carlo study of inhomogeneous neutron matter
We present an ab-initio study of neutron drops. We use Quantum Monte Carlo
techniques to calculate the energy up to 54 neutrons in different external
potentials, and we compare the results with Skyrme forces. We also calculate
the rms radii and radial densities, and we find that a re-adjustment of the
gradient term in Skyrme is needed in order to reproduce the properties of these
systems given by the ab-initio calculation. By using the ab-initio results for
neutron drops for close- and open-shell configurations, we suggest how to
improve Skyrme forces when dealing with systems with large isospin-asymmetries
like neutron-rich nuclei.Comment: 8 pages, 6 figures, talk given at Horizons on Innovative Theories,
Experiments, and Supercomputing in Nuclear Physics 2012, (HITES2012), New
Orleans, Louisiana, June 4-7, 2012; to appear in Journal of Physics:
Conference Series (JPCS
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