825 research outputs found
The Inclusive-Exclusive Connection and the Neutron Negative Central Charge Density
We find an interpretation of the recent finding that the central charge
density of the neutron is negative by using models of generalized parton
distributions at zero skewness to relate the behavior of deep inelastic
scattering quark distributions, evaluated at large values of Bjorken x, to the
transverse charge density evaluated at small distances. The key physical input
of these models is the Drell-Yan-West relation We find that the d quarks
dominate the neutron structure function for large values of Bjorken x, where
the large longitudinal momentum of the struck quark has a significant impact on
determining the center-of-momentum of the system, and thus the "center" of the
nucleon in the transverse position plane.Comment: 17 pages, 8 figures. Text of an invited talk presented by G. A.
Miller at the 2008 Division of Nuclear Physics Meeting in Oakland. Prepared
for Int. Journ. Mod. Phys.
Improvements to the Total Temperature Calibration of the NASA Glenn Icing Research Tunnel
The ability to accurately set repeatable total temperature conditions is critical for collecting quality icing condition data, particularly near freezing conditions. As part of efforts to continually improve data quality in the NASA Glenn Icing Research Tunnel (IRT), new facility instrumentation and new calibration hardware for total temperature measurement were installed and new operational techniques were developed and implemented. This paper focuses on the improvements made in the calibration of total temperature in the IRT
Momentum Transfer Dependence of Nuclear Transparency from the Quasielastic ^(12)C(e, e'p) Reaction
The cross section for quasielastic ^(12)C(e,e’p) scattering has been measured at momentum transfer Q^2=1, 3, 5, and 6.8 (GeV/c)^2. The results are consistent with scattering from a single nucleon as the dominant process. The nuclear transparency is obtained and compared with theoretical calculations that incorporate color transparency effects. No significant rise of the transparency with Q^2 is observed
Nucleon Form Factors - A Jefferson Lab Perspective
The charge and magnetization distributions of the proton and neutron are
encoded in their elastic electromagnetic form factors, which can be measured in
elastic electron--nucleon scattering. By measuring the form factors, we probe
the spatial distribution of the proton charge and magnetization, providing the
most direct connection to the spatial distribution of quarks inside the proton.
For decades, the form factors were probed through measurements of unpolarized
elastic electron scattering, but by the 1980s, progress slowed dramatically due
to the intrinsic limitations of the unpolarized measurements. Early
measurements at several laboratories demonstrated the feasibility and power of
measurements using polarization degrees of freedom to probe the spatial
structure of the nucleon. A program of polarization measurements at Jefferson
Lab led to a renaissance in the field of study, and significant new insight
into the structure of matter.Comment: 20 pages, 9 figures; Chapter in the book "A decade of Physics at
Jefferson Lab", to be published in Journal of Physics: Conference Serie
Measurement of the EMC Effect in the Deuteron
We determined the structure function ratio RdEMC=Fd2/(Fn2+Fp2) from recently published Fn2/Fd2 data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope dRdEMC/dx=−0.10 ± 0.05 in the range of Bjorken x from 0.35 to 0.7, for invariant mass W\u3e1.4 GeV and Q2\u3e1 GeV2 . The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses that find the EMC effect proportional to the probability of short-range nucleon-nucleon correlations
Polarization of Tau Leptons Produced in Quasielastic Neutrino--Nucleon Scattering
A numerical analysis of the polarization vector of tau leptons produced
through quasielastic neutrino and antineutrino interactions with free nucleons
is given with two models for vector electromagnetic form factors of proton and
neutron. The impact of G parity violating axial and vector second-class
currents is investigated by applying a simple heuristic model for the induced
scalar and tensor form factors.Comment: Thesis of a talk given at the 8th Scientific Conference (SCYSS-04),
Dubna, Russia, 2 - 6 Feb 2004. 11 pages, 6 figures; added references, figures
and discussion; conclusions unchange
Aero-Thermal Calibration of the NASA Glenn Icing Research Tunnel (2004 and 2005 Tests)
A full aero-thermal calibration of the NASA Glenn Icing Research Tunnel was completed in 2004 following the replacement of the inlet guide vanes upstream of the tunnel drive system and improvement to the facility total temperature instrumentation. This calibration test provided data used to fully document the aero-thermal flow quality in the IRT test section and to construct calibration curves for the operation of the IRT. The 2004 test was also the first to use the 2-D RTD array, an improved total temperature calibration measurement platform
All electromagnetic form factors
The electromagnetic form factors of spin-1/2 particles are known, but due to
historical reasons only half of them are found in many textbooks. Given the
importance of the general result, its model independence, its connection to
discrete symmetries and their violations we made an effort to derive and
present the general result based only on the knowledge of Dirac equation. We
discuss the phenomenology connected directly with the form factors, and spin
precession in external fields including time reversal violating terms. We apply
the formalism to spin-flip synchrotron radiation and suggest pedagogical
projects.Comment: Latex, 22 page
DonorNet and the Potential Effects on Organ Utilization
The evolution of communication as donor data flows from organ procurement organization to transplant centers has evolved with the incorporation of DonorNet 2007 ® into the UNet SM system. The ensuing study looks at DonorNet's impact on this process. We established defined time periods for comparison purposes. The study looked at match number for organ placement and overall organ utilization with a focus on ischemia time and graft outcomes. The results of the study demonstrate no significant change in the median match number of organ placement in liver or kidney transplantation. Changes in discard rates were varied amongst transplanted organs and there were noticeable changes in organ sharing with an increase in local allocation for kidney and liver and an ensuing decrease in regional and national distribution. There were no significant differences in the outcomes of livers and kidneys with low offer numbers compared with those with high offer numbers. Overall the study suggests a modest impact by DonorNet on organ placement and utilization, but a longer term study would need to be done to fully evaluate its impact.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79141/1/j.1600-6143.2010.03036.x.pd
Response: DonorNet and the Potential Effects on Organ Utilization
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79092/1/j.1600-6143.2010.03230.x.pd
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