1,290 research outputs found
R2D2 - a symmetric measurement of reactor neutrinos free of systematical errors
We discuss a symmetric setup for a reactor neutrino oscillation experiment
consisting of two reactors separated by about 1 km, and two symmetrically
placed detectors, one close to each reactor. We show that such a configuration
allows a determination of which is essentially free of
systematical errors, if it is possible to separate the contributions of the two
reactors in each detector sufficiently. This can be achieved either by
considering data when in an alternating way only one reactor is running or by
directional sensitivity obtained from the neutron displacement in the detector.Comment: 11 pages, 3 figures, clarifications added, some numbers in relation
with the neutron displacement corrected, version to appear in JHE
Quality of life after aortic valve repair is similar to Ross patients and superior to mechanical valve replacement: A cross-sectional study
Background: In patients after aortic valve surgery, the quality of life is hypothesized to be influenced by the type of the valve procedure. A cross-sectional study on the postoperative quality of life was carried out in patients after aortic valve-sparing surgery (with regards to the age of the patient), Ross procedure and mechanical aortic valve replacement. Methods: Quality of life was studied in 139 patients after aortic valve surgery divided into four study groups (Y - aortic valve-sparing procedure at the age below 50years, mean age 36.2years; O - aortic valve-sparing procedure at the age 50years and over, mean age 59.2years; R - Ross procedure, mean age 37.8years and M - mechanical aortic valve replacement at the age below 50years, mean age 39.2years). SF-36 Short Form and valve-specific questionnaires were mailed to the patients after 6months or later following surgery (median 26.9months). Results: In SF-36, the younger aortic valve repair patients and the Ross patients scored significantly better in 4 of 4 physical subscales and in 2 of 4 mental subscales than the older aortic valve repair and mechanical valve replacement patients. In the valve-specific questionnaire; however, all 3 groups free of anticoagulation (Y, O, and R) displayed greater freedom from negative valve-related concerns. Conclusions: Postoperative quality of life is influenced by the type of aortic valve procedure and is negatively linked with mechanical prosthesis implantation and long-term anticoagulation. Aortic valve-sparing strategy should be considered in cases with suitable valve morphology due to favorable clinical results and beneficial impact on the long-term quality of life
Antineutrino Geophysics with Liquid Scintillator Detectors
Detecting the antineutrinos emitted by the decay of radioactive elements in
the mantle and crust could provide a direct measurement of the total abundance
of uranium and thorium in the Earth. In calculating the antineutrino flux at
specific sites, the local geology of the crust and the background from the
world's nuclear power reactors are important considerations. Employing a global
crustal map, with type and thickness data, and using recent estimates of the
uranium and thorium distribution in the Earth, we calculate the antineutrino
event rate for two new neutrino detectors. We show that spectral features allow
terrestrial antineutrino events to be identified above reactor antineutrino
backgrounds and that the uranium and thorium contributions can be separately
determined.Comment: Published paper differs from original submitted preprint because
reviewers suggested updated continental crust U/Th abundances. Kamioka
geographical location error was in preprint, partially corrected in published
version. This version is the same as the published paper, with Kamioka fully
corrected. Because of recent interest in this topic, this version is being
made available, despite this work being 8 years ol
Formation of convective cells in the scrape-off layer of the CASTOR tokamak
Understanding of the scrape-off layer (SOL) physics in tokamaks requires
diagnostics with sufficient temporal and spatial resolution. This contribution
describes results of experiments performed in the SOL of the CASTOR tokamak
(R=40 cm, a = 6 cm) by means of a ring of 124 Langmuir probes surrounding the
whole poloidal cross section. The individual probes measure either the ion
saturation current of the floating potential with the spatial resolution up to
3 mm. Experiments are performed in a particular magnetic configuration,
characterized by a long parallel connection length in the SOL, L_par ~q2piR. We
report on measurements in discharges, where the edge electric field is modified
by inserting a biased electrode into the edge plasma. In particular, a complex
picture is observed, if the biased electrode is located inside the SOL. The
poloidal distribution of the floating potential appears to be strongly
non-uniform at biasing. The peaks of potential are observed at particular
poloidal angles. This is interpreted as formation of a biased flux tube, which
emanates from the electrode along the magnetic field lines and snakes q times
around the torus. The resulting electric field in the SOL is 2-dimensional,
having the radial as well as the poloidal component. It is demonstrated that
the poloidal electric field E_pol convects the edge plasma radially due to the
E_pol x B_T drift either inward or outward depending on its sign. The
convective particle flux is by two orders of magnitude larger than the
fluctuation-induced one and consequently dominates.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Probing Sterile Neutrino Parameters with Double Chooz, Daya Bay and RENO
In this work, we present a realistic analysis of the potential of the
present-day reactor experiments Double Chooz, Daya Bay and RENO for probing the
existence of sterile neutrinos. We present exclusion regions for sterile
oscillation parameters for each of these experiments, using simulations with
realistic estimates of systematic errors and detector resolutions, and compare
the sterile parameter sensitivity regions we obtain with the existing bounds
from other reactor experiments. We find that these experimental set-ups give
significant bounds on the parameter \Theta_{ee} especially in the low sterile
oscillation region 0.01 < \Delta m_{41}^2 < 0.05 eV^2. These bounds can add to
our understanding of the sterile neutrino sector since there is still a tension
in the allowed regions from different experiments for sterile parameters.Comment: 12 pages, 5 figure
Maximum likelihood analysis of the first KamLAND results
A maximum likelihood approach has been used to analize the first results from
KamLAND emphasizing the application of this method for low statistics samples.
The goodness of fit has been determined exploiting a simple Monte Carlo
approach in order to test two different null hytpotheses. It turns out that
with the present statistics the neutrino oscillation hypothesis has a
significance of about 90% (the best-fit for the oscillation parameters from
KamLAND are found to be: eV and
), while the no-oscillation hypothesis of
about 50%. Through the likelihood ratio the hypothesis of no disappearence is
rejected at about 99.9% C.L. with the present data from the positron spectrum.
A comparison with other analyses is presented.Comment: 14 pages, 5 figure
Status of the PICASSO Project
The Picasso project is a dark matter search experiment based on the
superheated droplet technique. Preliminary runs performed at the Picasso Lab in
Montreal have showed the suitability of this detection technique to the search
for weakly interacting cold dark matter particles. In July 2002, a new phase of
the project started. A batch of six 1-liter detectors with an active mass of
approximately 40g was installed in a gallery of the SNO observatory in Sudbury,
Ontario, Canada at a depth of 6,800 feet (2,070m). We give a status report on
the new experimental setup, data analysis, and preliminary limits on
spin-dependent neutralino interaction cross section.Comment: 3 pages, 2 figures. To appear in the Proceedings of the TAUP 2003
conference, 5-9 September, 2003, University of Washington, Seattle, US
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