2,116 research outputs found
Coulomb-nuclear interference in pion-nucleus bremsstrahlung
Pion-nucleus bremsstrahlung offers a possibility of measuring the structure
functions of pion-Compton scattering from a study of the
small-momentum-transfer region where the bremsstrahlung reaction is dominated
by the single-photon-exchange mechanism. The corresponding cross-section
distribution is characterized by a sharp peak at small momentum transfers. But
there is also a hadronic contribution which is smooth and constitutes an
undesired background. In this communication the modification of the
single-photon exchange amplitude by multiple-Coulomb scattering is investigated
as well as the Coulomb-nuclear interference term.Comment: 21 pages, 5 figures. Eqs.(51,52) corrected; some new figure
Hanbury-Brown and Twiss Intensity Correlations of Parabosons
This paper shows that in intensity correlation measurements there will be
clear and unambiguous signals that new-physics particles are, or aren't,
parabosons. For a parabosonic field in a dominant single-mode, there is a
diagonal P-representation in the "even and odd coherent states" basis. It is
used to analyze zero-time-interval intensity correlations of parabosons in a
maximum-entropic state. As the mean number of parabosons decreases, there is a
monotonic reduction to (2/p) of the constant bosonic ``factor of two''
proportionality of the second-order versus the squared first-order intensity
correlation function.Comment: 16 pages; version 4 to add simple p-independent recursion relatio
A Rational Risk Policy for Regulating Plant Diseases and Pests
Diseases and pests pose risks to U.S. agriculture and forests, but regulations and quarantines to control these risks are costly. The U.S. Department of Agriculture issues rules to control these risks based on economic analyses that do not take adequate account of links between risks and policy outcomes. A benefit-cost analysis that fully incorporates both the risk of a disease outbreak and the effect of regulations and quarantines on such risk can yield quite different conclusions. We apply methods that combine probabilistic risk assessments with economic analysis. We show that if USDA had incorporated risk into its benefit-cost analysis of Karnal bunt, a disease affecting wheat, it would have reached different conclusions about the impact of its actions. We estimate that suboptimal regulatory decisions in the case of Karnal bunt cost between 390 million per year. We recommend that USDA incorporate risk assessments into its economic analyses of proposed regulations.
Optimizing the Energy Efficiency of Short Term Ultra Reliable Communications in Vehicular Networks
We evaluate the use of HARQ schemes in the context of vehicle to infrastructure communications considering ultra reliable communications in the short term from a channel capacity stand point. We show that it is not possible to meet strict latency requirements with very high reliability without some diversity strategy and propose a solution to determining an optimal limit on the maximum allowed number of retransmissions using Chase combining and simple HARQ to increase energy efficiency. Results show that using the proposed optimizations leads to spending 5 times less energy when compared to only one retransmission in the context of a benchmark test case for urban scenario. In addition, we present an approximation that relates most system parameters and can predict whether or not the link can be closed, which is valuable for system design
Nuclear transparencies for nucleons, knocked-out under various semi-inclusive conditions
Using hadron dynamics we calculate nuclear transparencies for protons,
knocked-out in high-, semi-inclusive reactions. Predicted transparencies
are, roughly half a standard deviation above the NE18 data. The latter contain
the effects of binned proton missing momenta and mass, and of finite detector
acceptances. In order to test sensitivity we compare computed transparencies
without restrictions and the same with maximal cuts for missing momenta and the
electron energy loss. We find hardly any variation, enabling a meaningful
comparison with data and predictions based on hadron dynamics. Should
discrepancies persist in high-statistics data, the above may with greater
confidence be attributed to exotic components in the description of the
outgoing proton.Comment: 13 pages + 3 figsin appended PS file, report # WIS-94/43/Oct-P
Glauber-model analysis of total reaction cross sections for Ne, Mg, Si, and S isotopes with Skyrme-Hartree-Fock densities
A systematic analysis is made on the total reaction cross sections for Ne,
Mg, Si, and S isotopes. The high-energy nucleus-nucleus collision is described
based on the Glauber model. Using the Skyrme-Hartree-Fock method in the
three-dimensional grid-space representation, we determine the nuclear density
distribution for a wide range of nuclei self-consistently without assuming any
spatial symmetry. The calculated total reaction cross sections consistently
agree with the recent cross section data on NeC collision at
240\,MeV, which makes it possible to discuss the radius and deformation of
the isotopes. The total reaction cross sections for MgC, SiC
and SC cases are predicted for future measurements. We also find that
the high-energy cross section data for O, Ne, and Mg isotopes on a C
target at around 1000\,MeV can not be reproduced consistently with the
corresponding data at 240\,MeV.Comment: 10 pages, 14 figure
High energy neutrino in a nuclear environment: mirror asymmetry of the shadowing effect
The parity non-conservation effect in diffractive charged current DIS is
quantified in terms of color dipole sizes of left-handed and right-handed
electroweak bosons. We identify the origin and estimate the strength of the
left-right asymmetry effect and present comparison with experimental data on
the parity-odd structure function .
We study the shadowing effect in absorption of left-handed and right-handed
-bosons by atomic nuclei. The target nucleus is found to be quite
transparent for the charmed-strange Fock component of the light-cone in
the helicity state and rather opaque for the dipole with
.Comment: 11 pages, 2 figures, Talk presented at XXXIII International
Conference on High Energy Physics 26.07.06-02.08.06 Moscow, version to be
publishe
A Test of the Eikonal Approximation in High-Energy (e,e'p) Scattering
The Glauber method is extensively used to describe the motion of a hadronic
projectile in interaction with the surrounding nuclear medium. One of the main
approximations consists in the linearization of the wave equation for the
interacting particle. We have studied the consequences of such an assumption in
the case of the reaction
at high proton momenta by comparing the results with the predictions obtained
when all the ingredients of the calculation are unchanged but the second-order
differential equation for the scattered wave, which is solved exactly for each
partial wave up to a maximum of 120 spherical harmonics. We find that the
Glauber cross section is always larger by a factor , even at
vanishing missing momenta. We give a quantum-mechanical explanation of this
discrepancy. Nevertheless, a good correlation is found between the two
predictions as functions of the missing momentum, especially in parallel
kinematics.Comment: LaTeX, 8 pages, 4 figures uuencoded, accepted for publication on
Phys. Lett.
Some Remarks on Quantum Coherence
There are many striking phenomena which are attributed to
``quantum coherence''. It is natural to wonder if there are new quantum
coherence effects waiting to be discovered which could lead to interesting
results and perhaps even practical applications. A useful starting point for
such discussions is a definition of ``quantum coherence''. In this article I
give a definition of quantum coherence and use a number of illustrations to
explore the implications of this definition. I point to topics of current
interest in the fields of cosmology and quantum computation where questions of
quantum coherence arise, and I emphasize the impact that interactions with the
environment can have on quantum coherence.Comment: 25 pages plain LaTeX, no figures. More references have been added and
typos have been corrected. Journal of Modern Optics, in press.
Imperial/TP/93-94/1
Energy and Cost Analysis of Cellular Networks Under Co-Channel Interference
In this paper we carry out an energy efficiency and economic cost analysis of different cellular network designs. Our system model considers the co-channel interference, different amounts of available bandwidths and also the reuse of frequencies. The energy efficiency analysis employs a realistic power consumption model, while the economic analysis focus on infrastructure, spectrum licenses, and energy costs. Our results show that from an economic point of view the bandwidth cost and the number of employed base stations can be the most relevant factors to be balanced, while from an energy efficiency analysis it is more interesting to employ larger bandwidths and to balance the reuse of frequencies and the number of base stations. Moreover, although the system design under these two different points of view can be rather different, we also look into scenarios when the most energy efficient system design may also lead to the best economic option
- …