997 research outputs found
Letter from J. G. Arrington to T. B. Larimore
Letter from J. G. Arrington to T. B. Larimore. The one-page handwritten correspondence is on Dismukes & Arrington letterhead and is dated 19 December 1912. There is a transcript of the letter in the item PDF
On the physics behind the form factor ratio
We point out that there exist two natural definitions of the nucleon
magnetization densities : the density introduced in Kelly's
phenomenological analysis and theoretically more standard one . We
can derive an explicit analytical relation between them, although Kelly's
density is more useful to disentangle the physical origin of the different
dependence of the Sachs electric and magnetic form factors of the
nucleon. We evaluate both of and as well as the
charge density of the proton within the framework of the chiral
quark soliton model, to find a noticeable qualitative difference between
and , which is just consistent with Kelly's result
obtained from the empirical information on the Sachs electric and magnetic form
factors of the proton.Comment: 12 pages, 5 figures. version to appear in J. Phys. G.: Nucl. Part.
Phy
Coherent π^0 photoproduction on the deuteron up to 4 GeV
The differential cross section for ^2H(γ,d)π^0 has been measured at deuteron center-of-mass angles of 90° and 136°. This work reports the first data for this reaction above a photon energy of 1 GeV, and permits a test of the apparent constituent counting rule and reduced nuclear amplitude behavior as observed in elastic ed scattering. Measurements were performed up to a photon energy of 4.0 GeV, and are in good agreement with previous lower energy measurements. Overall, the data are inconsistent with both constituent-counting rule and reduced nuclear amplitude predictions
How well do we know the neutron structure function?
We present a detailed analysis of the uncertainty in the neutron F2n
structure function extracted from inclusive deuteron and proton deep-inelastic
scattering data. The analysis includes experimental uncertainties as well as
uncertainties associated with the deuteron wave function, nuclear smearing, and
nucleon off-shell corrections. Consistently accounting for the Q^2 dependence
of the data and calculations, and restricting the nuclear corrections to
microscopic models of the deuteron, we find significantly smaller uncertainty
in the extracted F2n/F2p ratio than in previous analyses. In addition to
yielding an improved extraction of the neutron structure function, this
analysis also provides an important baseline that will allow future,
model-independent extractions of neutron structure to be used to examine
nuclear medium effects in the the deuteron.Comment: 5 pages, 6 figure
A New Extraction of Neutron Structure Functions from Existing Inclusive DIS Data
A recent reanalysis of world proton and deuteron structure function
measurements showed that a significant amount of the apparent model dependence
in the extraction of the neutron structure function was related to
inconsistencies between the kinematics of the data and those assumed for the
calculation, suggesting that the true model dependence is smaller than commonly
believed. We present a detailed comparison of the neutron structure function as
extracted using different models, with care taken to ensure that all other
aspects of the comparison are done consistently. The neutron structure function
is extracted using a fit to these data evaluated at fixed Q^2_0=16 GeV^2. We
compare the results obtained using a variety of N--N potentials and deuteron
binding models to determine the model dependence of the extraction. As in the
recent extraction, F_{2n}/F_{2p} falls with x with no sign of plateau and
follows the low edge of the wide range of earlier F_{2n} extractions. The
model-dependent uncertainty in F_{2n}/F_{2p} is shown to be considerably
smaller than previously believed, particularly at large-x.Comment: Proceedings for the 3rd International Workshop on Nucleon Structure
at Large Bjorken x, Jefferson Lab, October 13-15, 2010 Updates made to text
and one figure adde
Final Report for the Success of African American Students (SAAS) in Independent Schools project
The Success of African American Students (SAAS) in Independent Schools was a collaborative, longitudinal, mixed-method research project focused on investigating and understanding the variety of social, emotional, and institutional factors that were thought to influence how Black students navigate the independent school environment. SAAS involved researchers from the University of Pennsylvania (Penn) Graduate School of Education working with faculty and staff from several Philadelphia area independent schools. The SAAS project was supported by five years of funding from the National Institute of Mental Health (NIMH). Finally, SAAS utilized qualitative methods such as focus groups and semi-structured interviews as well as quantitative methods such as questionnaire surveys and behavioral observations
Effect of configuration modification on the hypersonic aerodynamic characteristics of a blended delta wing-body entry vehicle
The longitudinal, lateral, and directional aerodynamic characteristics of a delta-wing configuration were obtained experimentally at Mach 20 in helium with Reynolds numbers, based on model length, of 1.5 million and 2.9 million and at a Mach number of 6 in air with a Reynolds number, based on model length, of 4.8 million. The angles of attack varied from 0 deg to 55 deg for two sideslip angles. The effects of the addition of dorsal fins, the removal of wing tip fins, an increase in elevon span, and changes in elevon hinge-line sweep angle are discussed. The unmodified vehicle had a maximum lift-drag ratio of 2.1 at Mach 19 and of 2.4 at Mach 6 with about the same lateral and directional stability level at both Mach numbers. As the Mach number increased from 6 to 20, the longitudinal center of pressure moved forward and more positive elevon deflection was therefore required to maintain a given trim angle. The removal of wing tip fins increased the maximum lift-drag ratio and had a negligible effect on longitudinal stability, but caused directional instability that was not corrected by the dorsal fins examined. The shape of the wing and elevon hinge-line sweep had a large influence on the induced yawing moment due to roll control
Evidence for virtual Compton scattering from the proton
In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation
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 electromagnetic form factors
Elastic electromagnetic nucleon form factors have long provided vital
information about the structure and composition of these most basic elements of
nuclear physics. The form factors are a measurable and physical manifestation
of the nature of the nucleons' constituents and the dynamics that binds them
together. Accurate form factor data obtained in recent years using modern
experimental facilities has spurred a significant reevaluation of the nucleon
and pictures of its structure; e.g., the role of quark orbital angular
momentum, the scale at which perturbative QCD effects should become evident,
the strangeness content, and meson-cloud effects. We provide a succinct survey
of the experimental studies and theoretical interpretation of nucleon
electromagnetic form factors.Comment: Topical review invited by Journal of Physics G: Nuclear and Particle
Physics; 34 pages (contents listed on page 34), 11 figure
- …