3,484 research outputs found
Consistent analysis of neutral- and charged-current neutrino scattering off carbon
Background: Good understanding of the cross sections for (anti)neutrino
scattering off nuclear targets in the few-GeV energy region is a prerequisite
for correct interpretation of results of ongoing and planned oscillation
experiments.
Purpose: Clarify possible source of disagreement between recent measurements
of the cross sections on carbon.
Method: Nuclear effects in (anti)neutrino scattering off carbon nucleus are
described using the spectral function approach. The effect of two- and
multi-nucleon final states is accounted for by applying an effective value of
the axial mass, fixed to 1.23 GeV. Neutral-current elastic (NCE) and
charged-current quasielastic (CCQE) processes are treated on equal footing.
Results: The differential and total cross sections for the energy ranging
from a few hundreds of MeV to 100 GeV are obtained and compared to the
available data from the BNL E734, MiniBooNE, and NOMAD experiments.
Conclusions: Nuclear effects in NCE and CCQE scattering seem to be very
similar. Within the spectral function approach, the axial mass from the shape
analysis of the MiniBooNE data is in good agreement with the results reported
by the BNL E734 and NOMAD Collaborations. However, the combined analysis of NCE
and CCQE data does not seem to support the contribution of multi-nucleon final
states being large enough to explain the normalization of the
MiniBooNE-reported cross sections.Comment: 14 pages, 9 figures, detailed discussion of the role of FSI is adde
The UK Defence Review recognises the immediate risks yet provides solutions that are years away
In publishing the latest National Security Strategy (NSS) and Strategic Defence and Security Review (SDSR) in November 2015 the government managed to deliver quite a feat. The usual defence ‘commentariat’ was largely silenced as their worst fears appeared to be assuaged. Instead of cuts that many had first feared, this review promised a whole series of improvements. However, as Andrew M Dorman points out, these promises rest on a number of flawed assumptions, which continue to dog defence policy in the UK
The Spatial Distribution Of OH And CN Radicals In The Coma Of Comet Encke
Multiple potential parent species have been proposed to explain CN abundances in comet comae, but the parent has not been definitively identified for all comets. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Comet Encke is the shortest orbital period (3.3 years) comet known and also has a low dust-to-gas ratio based on optical observations. Observations of CN were obtained from 2003 October 22 to 24, using the 2.7 m telescope at McDonald Observatory. To determine the parent of CN, the classical vectorial model was modified by using a cone shape in order to reproduce Encke's highly aspherical and asymmetric coma. To test the robustness of the modified model, the spatial distribution of OH was also modeled. This also allowed us to obtain CN/OH ratios in the coma. Overall, we find the CN/OH ratio to be 0.009 +/- 0.004. The results are consistent with HCN being the photodissociative parent of CN, but we cannot completely rule out other possible parents such as CH(3)CN and HC(3)N. We also found that the fan-like feature spans similar to 90 degrees, consistent with the results of Woodney et al..NASAOffice of the Vice President for Research and Economic Development at Mississippi State UniversityMcDonald Observator
European Adaptation to Expeditionary Warfare: Implications for the U.S. Army
The author briefly examines the European response to the changing security environment and the opportunities presented by the European Security and Defense Policy Expeditionary Force. As he correctly observes, the establishment of a European expeditionary force will be no easy matter, will require substantial investment, and will take years to complete. However, it is the right course for Europe to take. The European Union (EU) cannot manage emerging security issues using Cold War legacy forces because they are too ponderous to deploy. A lighter, more nimble expeditionary force is critical to EU policy. The author also points out that the United States must remain involved in the EU initiatives. Europe cannot go it alone and will need advice and perhaps even material support if it is to realize its ambitious agenda.https://press.armywarcollege.edu/monographs/1809/thumbnail.jp
The expected cosmic ray density and stream distributions at the heliolatitudinal asymmetry of solar wind
The results of the spatial distribution of cosmic ray density, gradients, and anisotropy obtained on the basis of the numerical solution of the anisotropic diffusion equation with an account of solar wind velocity change depending on the latitudinal angle theta of the form U=u sub oe sup alpha theta and the diffusion coefficient depending on the spatial coordinates and the particle rigidity are presented. It is shown that the increase of the solar wind velocity and the diffusion coefficient with heliolatitude leads to gradient distributions that are in accord with experimental data observed in space. The results of the energetic spectrum of 11 and 22-year cosmic ray variations obtained with an account of direction of the general magnetic field of the Sun are presented are given
A guide for performing system safety analysis
A general guide is presented for performing system safety analyses of hardware, software, operations and human elements of an aerospace program. The guide describes a progression of activities that can be effectively applied to identify hazards to personnel and equipment during all periods of system development. The general process of performing safety analyses is described; setting forth in a logical order the information and data requirements, the analytical steps, and the results. These analyses are the technical basis of a system safety program. Although the guidance established by this document cannot replace human experience and judgement, it does provide a methodical approach to the identification of hazards and evaluation of risks to the system
Possible High-Redshift, Low-Luminosity AGN Activity in the Hubble Deep Field
In the Hubble Deep Field (HDF), twelve candidate sources of high-redshift (z
> 3.5) AGN activity have been identified. The color selection criteria were
established by passing spectra of selected quasars and Seyfert galaxies
(appropriately redshifted and modified for "Lyman forest" absorption), as well
as stars, observed normal and starburst galaxies, and galaxy models for various
redshifts through the filters used for the HDF observations. The actual
identification of AGN candidates also involved convolving a
Laplacian-of-Gaussian filter with the HDF images, thereby removing relatively
flat galactic backgrounds and leaving only the point-like components in the
centers. Along with positions and colors, estimated redshifts and absolute
magnitudes are reported, with the candidates falling toward the faint end of
the AGN luminosity function. One candidate has been previously observed
spectroscopically, with a measured redshift of 4.02. The number of sources
reported here is consistent with a simple extrapolation of the observed quasar
luminosity function to magnitude 30 in B_Johnson. Implications for ionization
of the intergalactic medium and for gravitational lensing are discussed.Comment: 10 pages LaTex plus 2 separate files (Table 1 which is a two-page
landscape LaTex file; and Figure 6 which is a large (0.7 MB) non-encapsulated
postscript file). Accepted for publication in the Astronomical Journa
Coupling functions for lead and lead-free neutron monitors from the latitudinal measurements performed in 1982 in the research station Academician Kurchatov
The latitudinal behavior of intensities and multiplicities was registered by the neutron monitor 2 NM and the lead-free neutron monitor 3 SND (slow-neuron detector) in the equator-Kaliningrad line in the Atlantic Ocean. Coupling coefficients for 3 SND show the sensitivity of this detector to primary particles of cosmic rays of energies on the average lower than for 2 NM. As multiplicities increase, the coupling coefficients shift towards higher energies
Results from the Apollo passive seismic experiment
Recent results from the Apollo seismic network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km; and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. The best model for the zone of original differentiation appears to be a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro; overlying an ultramafic cumulate (olivine-pyroxene) about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals has recently been identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes
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