454 research outputs found
Search for the Lepton-Number-Violating Decay
A sensitive search for the lepton-number-violating decay has been performed using a sample of hyperons
produced in 800 GeV/ -Cu collisions. We obtain at 90% confidence, improving on the best
previous limit by four orders of magnitude.Comment: 9 pages, 5 figures, to be published in Phys. Rev. Let
Structural and Electronic Properties of Small Neutral (MgO)n Clusters
Ab initio Perturbed Ion (PI) calculations are reported for neutral
stoichiometric (MgO)n clusters (n<14). An extensive number of isomer structures
was identified and studied. For the isomers of (MgO)n (n<8) clusters, a full
geometrical relaxation was considered. Correlation corrections were included
for all cluster sizes using the Coulomb-Hartree-Fock (CHF) model proposed by
Clementi. The results obtained compare favorably to the experimental data and
other previous theoretical studies. Inclusion of correlaiotn is crucial in
order to achieve a good description of these systems. We find an important
number of new isomers which allows us to interpret the experimental magic
numbers without the assumption of structures based on (MgO)3 subunits. Finally,
as an electronic property, the variations in the cluster ionization potential
with the cluster size were studied and related to the structural isomer
properties.Comment: 24 pages, LaTeX, 7 figures in GIF format. Accepted for publication in
Phys. Rev.
Interface controlled electrical and magnetic properties in Fe–Fe3O4–silica gel nanocomposites
Measurement of the Alpha Asymmetry Parameter for the Omega- to Lambda K- Decay
We have measured the alpha parameter of the Omega- to Lambda K- decay using
data collected with the HyperCP spectrometer during the 1997 fixed-target run
at Fermilab. Analyzing a sample of 0.96 million Omega- to Lambda K^-, Lambda to
p pi- decays, we obtain alpha_Omega*alpha_Lambda =
[1.33+/-0.33(stat)+/-0.52(syst)] x 10^{-2}. With the accepted value of
alpha_Lambda, alpha_Omega is found to be [2.07+/-0.51(stat)+/-0.81(syst)] x
10^{-2}.Comment: 5 pages, 4 figures, to be appeared as a Rapid Communication in Phys.
Rev.
Inequality of access in irrigation systems of the mid-hills of Nepal
Access to, and control over, water for irrigation is one of the most important factors for increasing agricultural productivity, thereby affecting household food security and levels of poverty in developing countries. However, investments in the irrigation sector have often failed to consider equity aspects of irrigation interventions. Using data from 199 households from three irrigation systems in the mid-hills of Nepal, we analyse access and control of water in different levels of socio-economic heterogeneities. The results demonstrate that efforts to improve livelihoods of the rural poor should give due consideration to the distributional aspects of irrigation interventions, with authority for allocating the level of access to irrigation water given to the farmers throughout the system
Calculation of The Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals
The band gap energy as well as the possibility of cross luminescence
processes in alkaline-earth dihalide crystals have been calculated using the ab
initio Perturbed-Ion (PI) model. The gap is calculated in several ways: as a
difference between one-electron energy eigenvalues and as a difference between
total energies of appropriate electronic states of the crystal, both at the HF
level and with inclusion of Coulomb correlation effects. In order to study the
possibility of ocurrence of cross luminescence in these materials, the energy
difference between the valence band and the upmost core band for some
representative crystals has been calculated. Both calculated band gap energies
and cross luminescence predictions compare very well with the available
experimental results.Comment: LaTeX file containing 8 pages plus 1 postscript figure. Final version
accepted for publication in The Journal of the Physical Society of Japan. It
contains a more complete list of references, as well as a more detailed
comparison with previous theoretical investigations on the subjec
Evidence for the Decay Sigma+ -> p mu+ mu-
We report the first evidence for the decay Sigma+ -> p mu+ mu- from data
taken by the HyperCP experiment(E871) at Fermilab. Based on three observed
events, the branching ratio is B(Sigma+ -> p,mu+,mu-) = [8.6 +6.6,-5.4(stat)
+/-5.5(syst)] x 10**-8. The narrow range of dimuon masses may indicate that the
decay proceeds via a neutral intermediate state, Sigma+ -> p P0, P0 -> mu+ mu-,
with a P0 mass of 214.3 +/- 0.5 MeV/c**2 and branching ratio B(Sigma+ -> p P0;
P0 -> mu+ mu-) = [3.1 +2.4,-1.(stat) +/-1.5(syst)] x 10**-8.Comment: As published in PR
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