391 research outputs found
Past, Present and Future Perspectives on Groundnut Breeding in Burkina Faso
Groundnut (Arachis hypogaea L.) is a major food and cash crop in Burkina Faso. Due to
the growing demand for raw oilseeds, there is an increasing interest in groundnut production from
traditional rain-fed areas to irrigated environments. However, despite implementation of many
initiatives in the past to increase groundnut productivity and production, the groundnut industry still
struggles to prosper due to the fact of several constraints including minimal development research
and fluctuating markets. Yield penalty due to the presence of drought and biotic stresses continue
to be a major drawback for groundnut production. This review traces progress in the groundnut
breeding that started in Burkina Faso before the country’s political independence in 1960 through to
present times. Up to the 1980s, groundnut improvement was led by international research institutions
such as IRHO (Institute of Oils and Oleaginous Research) and ICRISAT (International Crops Research
Institute for the Semi-Arid Tropics). However, international breeding initiatives were not su�cient to
establish a robust domestic groundnut breeding programme. This review also provides essential
information about opportunities and challenges for groundnut research in Burkina Faso, emphasising
the need for institutional attention to genetic improvement of the crop
High-Sensitivity Measurement of 3He-4He Isotopic Ratios for Ultracold Neutron Experiments
Research efforts ranging from studies of solid helium to searches for a
neutron electric dipole moment require isotopically purified helium with a
ratio of 3He to 4He at levels below that which can be measured using
traditional mass spectroscopy techniques. We demonstrate an approach to such a
measurement using accelerator mass spectroscopy, reaching the 10e-14 level of
sensitivity, several orders of magnitude more sensitive than other techniques.
Measurements of 3He/4He in samples relevant to the measurement of the neutron
lifetime indicate the need for substantial corrections. We also argue that
there is a clear path forward to sensitivity increases of at least another
order of magnitude.Comment: 11 pages, 10 figure
Studies of MCP-PMTs in the miniTimeCube neutrino detector
This report highlights two different types of cross-talk in the
photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube
detector has 24 -anode Photonis MCP-PMTs Planacon XP85012,
totalling 1536 individual pixels viewing the 2-liter cube of plastic
scintillator
Precision Measurement of the Radiative Decay of the Free Neutron
The standard model predicts that, in addition to a proton, an electron, and
an antineutrino, a continuous spectrum of photons is emitted in the
decay of the free neutron. We report on the RDK II experiment which measured
the photon spectrum using two different detector arrays. An annular array of
bismuth germanium oxide scintillators detected photons from 14 to 782~keV. The
spectral shape was consistent with theory, and we determined a branching ratio
of 0.00335 0.00005 [stat] 0.00015 [syst]. A second detector array
of large area avalanche photodiodes directly detected photons from 0.4 to
14~keV. For this array, the spectral shape was consistent with theory, and the
branching ratio was determined to be 0.00582 0.00023 [stat] 0.00062
[syst]. We report the first precision test of the shape of the photon energy
spectrum from neutron radiative decay and a substantially improved
determination of the branching ratio over a broad range of photon energies
Search for a T-odd, P-even Triple Correlation in Neutron Decay
Background: Time-reversal-invariance violation, or equivalently CP violation,
may explain the observed cosmological baryon asymmetry as well as signal
physics beyond the Standard Model. In the decay of polarized neutrons, the
triple correlation D\cdot(p_{e}\timesp_{\nu}) is a parity-even,
time-reversal- odd observable that is uniquely sensitive to the relative phase
of the axial-vector amplitude with respect to the vector amplitude. The triple
correlation is also sensitive to possible contributions from scalar and tensor
amplitudes. Final-state effects also contribute to D at the level of 1e-5 and
can be calculated with a precision of 1% or better. Purpose: We have improved
the sensitivity to T-odd, P-even interactions in nuclear beta decay. Methods:
We measured proton-electron coincidences from decays of longitudinally
polarized neutrons with a highly symmetric detector array designed to cancel
the time-reversal-even, parity-odd Standard-Model contributions to polarized
neutron decay. Over 300 million proton-electron coincidence events were used to
extract D and study systematic effects in a blind analysis. Results: We find D
= [-0.94\pm1.89(stat)\pm0.97(sys)]e-4. Conclusions: This is the most sensitive
measurement of D in nuclear beta decay. Our result can be interpreted as a
measurement of the phase of the ratio of the axial-vector and vector coupling
constants (CA/CV= |{\lambda}|exp(i{\phi}_AV)) with {\phi}_AV = 180.012{\deg}
\pm0.028{\deg} (68% confidence level) or to constrain time-reversal violating
scalar and tensor interactions that arise in certain extensions to the Standard
Model such as leptoquarks. This paper presents details of the experiment,
analysis, and systematic- error corrections.Comment: 21 pages, 22 figure
emiT: an apparatus to test time reversal invariance in polarized neutron decay
We describe an apparatus used to measure the triple-correlation term (\D
\hat{\sigma}_n\cdot p_e\times p_\nu) in the beta-decay of polarized neutrons.
The \D-coefficient is sensitive to possible violations of time reversal
invariance. The detector has an octagonal symmetry that optimizes
electron-proton coincidence rates and reduces systematic effects. A beam of
longitudinally polarized cold neutrons passes through the detector chamber,
where a small fraction beta-decay. The final-state protons are accelerated and
focused onto arrays of cooled semiconductor diodes, while the coincident
electrons are detected using panels of plastic scintillator. Details regarding
the design and performance of the proton detectors, beta detectors and the
electronics used in the data collection system are presented. The neutron beam
characteristics, the spin-transport magnetic fields, and polarization
measurements are also described.Comment: 15 pages, 13 figure
- …