1,950 research outputs found
A diagrammatic treatment of neutrino oscillations
We present a covariant wave-packet approach to neutrino flavor transitions in
vacuum. The approach is based on the technique of macroscopic Feynman diagrams
describing the lepton number violating processes of production and absorption
of virtual massive neutrinos at the macroscopically separated space-time
regions ("source" and "detector"). Accordingly, the flavor transitions are a
result of interference of the diagrams with neutrinos of different masses in
the intermediate states. The statistically averaged probability of the process
is representable as a multidimensional integral of the product of the factors
which describe the differential flux density of massless neutrinos from the
source, differential cross section of the neutrino interaction with the
detector and a dimensionless factor responsible for the flavor transition. The
conditions are analyzed under which the last factor can be treated as the
flavor transition probability in the usual quantum-mechanical sense.Comment: 27 pages,7 figures, iopart class. Includes minor corrections made in
proofs. References update
Effect of the C-bridge length on the ultraviolet-resistance of oxycarbosilane low-k films
The ultra-violet (UV) and vacuum ultra-violet (VUV) resistance of bridging alkylene groups in organosilica films has been investigated. Similar to the Si-CH3 (methyl) bonds, the Si-CH2-Si (methylene) bonds are not affected by 5.6 eV irradiation. On the other hand, the concentration of the Si-CH2-CH2-Si (ethylene) groups decreases during such UV exposure. More significant difference in alkylene reduction is observed when the films are exposed to VUV (7.2 eV). The ethylene groups are depleted by more than 75% while only about 40% methylene and methyl groups loss is observed. The different sensitivity of bridging groups to VUV light should be taken into account during the development of curing and plasma etch processes of low-k materials based on periodic mesoporous organosilicas and oxycarbosilanes. The experimental results are qualitatively supported by ab-initio quantum-chemical calculations
Lepton Polarization in Neutrino-Nucleon Interactions
We derive generic formulas for the polarization density matrix of leptons
produced in neutrino and antineutrino collisions and briefly consider some
important particular cases. Next we employ the general formalism in order to
include the final lepton mass and spin into the popular model by Rein and
Sehgal for single pion neutrinoproduction.Comment: Talk given at 10th International Workshop on High-Energy Spin Physics
(SPIN 03), Dubna, Russia, 16-20 Sep 2003. 12 pages; extended version, typos
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Low Earth orbit thermal control coatings exposure flight tests: A comparison of U.S. and Russian results
Both the United States (US) and Russia have conducted a variety of space environment effects on materials (SEEM) flight experiments in recent years. A prime US example was the Long Duration Exposure Facility (LDEF), which spent 5 years and 9 months in low Earth orbit (LEO) from April 1984 to January 1990. A key Russian experiment was the Removable Cassette Container experiment, (RCC-1), flown on the Mir Orbital Station from 11 January 1990 to 26 April 1991. This paper evaluates the thermal control coating materials data generated by these two missions by comparing: environmental exposure conditions, functionality and chemistry of thermal control coating materials, and pre- and post-flight analysis of absorptance, emittance, and mass loss due to atomic oxygen erosion. It will be seen that there are noticeable differences in the US and Russian space environment measurements and models, which complicates comparisons of environments. The results of both flight experiments confirm that zinc oxide and zinc oxide orthotitanate white thermal control paints in metasilicate binders (Z93, YB71, TP-co-2, TP-co-11, and TP-co-12), are the most stable upon exposure to the space environment. It is also seen that Russian flight materials experience broadens to the use of silicone and acrylic resin binders while the US relies more heavily on polyurethane
New Test of Supernova Electron Neutrino Emission using Sudbury Neutrino Observatory Sensitivity to the Diffuse Supernova Neutrino Background
Supernovae are rare nearby, but they are not rare in the Universe, and all
past core-collapse supernovae contributed to the Diffuse Supernova Neutrino
Background (DSNB), for which the near-term detection prospects are very good.
The Super-Kamiokande limit on the DSNB electron {\it antineutrino} flux,
cm s, is just above the
range of recent theoretical predictions based on the measured star formation
rate history. We show that the Sudbury Neutrino Observatory should be able to
test the corresponding DSNB electron {\it neutrino} flux with a sensitivity as
low as cm s,
improving the existing Mont Blanc limit by about three orders of magnitude.
While conventional supernova models predict comparable electron neutrino and
antineutrino fluxes, it is often considered that the first (and
forward-directed) SN 1987A event in the Kamiokande-II detector should be
attributed to electron-neutrino scattering with an electron, which would
require a substantially enhanced electron neutrino flux. We show that with the
required enhancements in either the burst or thermal phase fluxes, the
DSNB electron neutrino flux would generally be detectable in the Sudbury
Neutrino Observatory. A direct experimental test could then resolve one of the
enduring mysteries of SN 1987A: whether the first Kamiokande-II event reveals a
serious misunderstanding of supernova physics, or was simply an unlikely
statistical fluctuation. Thus the electron neutrino sensitivity of the Sudbury
Neutrino Observatory is an important complement to the electron antineutrino
sensitivity of Super-Kamiokande in the quest to understand the DSNB.Comment: 10 pages, 3 figure
Alternative pathways of the initial transformation of 2,4,6-trinitrotoluene by yeasts
A new model for the initial transformation of 2,4,6-trinitrotoluene (TNT) by facultatively anaerobic and aerobic yeasts is presented. The model is based on the data that Saccharomyces sp. ZS-Al was able to reduce the nitrogroups of TNT with the formation of 2- and 4-hydroxyaminodinitrotoluenes (2-HADNT and 4-HADNT) as the major early TNT metabolites (the molar HADNT/TNT ratio reached 0.81), whereas aminodinitrotoluenes (ADNTs) and the hydride-Meisenheimer complex of TNT (H-TNT) were the minor products. Candida sp. AN-L13 almost completely transformed TNT into H-TNT through the reduction of the aromatic ring. Candida sp. AN-L14 transformed TNT through a combination of the two mechanisms described. Aeration stimulated the production of HADNT from TNT, whereas yeast incubation under stationary conditions promoted the formation of HADNT. The transformation of TNT into HADNT led to a tenfold increase in the acute toxicity of the TNT preparation with respect to Paramecium caudatum, whereas the increase in the toxicity was about twofold in the case of the alternative attack at the aromatic ring
Alternative pathways of the initial transformation of 2,4,6-trinitrotoluene by yeasts
A new model for the initial transformation of 2,4,6-trinitrotoluene (TNT) by facultatively anaerobic and aerobic yeasts is presented. The model is based on the data that Saccharomyces sp. ZS-Al was able to reduce the nitrogroups of TNT with the formation of 2- and 4-hydroxyaminodinitrotoluenes (2-HADNT and 4-HADNT) as the major early TNT metabolites (the molar HADNT/TNT ratio reached 0.81), whereas aminodinitrotoluenes (ADNTs) and the hydride-Meisenheimer complex of TNT (H-TNT) were the minor products. Candida sp. AN-L13 almost completely transformed TNT into H-TNT through the reduction of the aromatic ring. Candida sp. AN-L14 transformed TNT through a combination of the two mechanisms described. Aeration stimulated the production of HADNT from TNT, whereas yeast incubation under stationary conditions promoted the formation of HADNT. The transformation of TNT into HADNT led to a tenfold increase in the acute toxicity of the TNT preparation with respect to Paramecium caudatum, whereas the increase in the toxicity was about twofold in the case of the alternative attack at the aromatic ring. © 2002 MAIK "Nauka/Interperiodica"
Large Non-perturbative Effects of Small \Delta m^2_{21}/\Delta m^2_{31} and \sin \theta_{13} on Neutrino Oscillation and CP Violation in Matter
In the framework of three generations, we consider the CP violation in
neutrino oscillation with matter effects. At first, we show that the
non-perturbative effects of two small parameters, \Delta m_{21}^2/\Delta
m_{31}^2 and \sin \theta_{13}, become more than 50% in certain ranges of energy
and baseline length. This means that the non-perturbative effects should be
considered in detailed analysis in the long baseline experiments. Next, we
propose a method to include these effects in approximate formulas for
oscillation probabilities. Assuming the two natural conditions,
\theta_{23}=45^\circ and the fact that the matter density is symmetric, a set
of approximate formulas, which involve the non-perturbative effects, has been
derived in all channels.Comment: 25 pages, 4 figures, version to appear in JHE
Roughness coefficient of the Instruch riverbed
The article presents the results of improving the numerical method developed in [1-3] for calculating the roughness coefficient of the riverbed (RCOTR) to increase stability and using it to study the dependence of the RCOTR of the Instruch River on dimensionless complexes in different seasons
Fluxes of atmospheric muons underwater depending on the small-x gluon density
The prompt muon contribution to the deep-sea atmospheric muon flux can serve
as a tool for probing into the small-x feature of the gluon density inside of a
nucleon, if the muon energy threshold could be lifted to 100 TeV. The prompt
muon flux underwater is calculated taking into consideration predictions of
recent charm production models in which the small-x behaviour of the gluon
distribution is probed. We discuss the possibility of distinguishing the PQCD
models of the charm production differing in the small-x exponent of the gluon
distribution, in measurements of the muon flux at energies 10-100 TeV with
neutrino telescopes.Comment: 9 pages, 4 eps figures, uses iopart.st
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