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Update of the major results from the GALLEX Cr-neutrino source experiment
This report provides an update about the major results of the GALLEX Cr-neutrino source experiment since November 8, 1994 and reports results of individual measurements of source activity. New data does not change the main conclusion from the November 8, 1994 data: Unknown systematical errors in GALLEX can at the most be of order 10%. 3 refs., 1 fig., 2 tabs
Atmospheric neutrino oscillations in three-flavor neutrinos
We analyzed the atmospheric neutrino experiments of SuperKamiokande including
zenith angle dependence's using the three-flavor neutrino framework with the
hierarchy m^2_1 \approx m^2_2<<m^2_3. Taking into account the terrestrial,
solar neutrino experimental data and the atmospheric neutrino experiments
including the sub-GeV and multi-GeV data in SuperKamiokande, large angle
solution in the solar neutrino experiments is favored and the range of the mass
parameter Deltam^2_{23} is restricted between 0.08eV^2 - 2eV^2. Allowed regions
of mixing parameters are (theta_{13}<4degree, 27degree<theta_{23}< 32degree)
for Delta m_{23}^2=1eV^2 and (theta_{13}<3degree, 28degree<theta_{23}
<33degree) for Deltam_{23}^2=0.1 eV^2.Comment: 21 pages, LaTe
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
The Problem of Large Leptonic Mixing
Unlike in the quark sector where simple permutation symmetries can
generate the general features of quark masses and mixings, we find it
impossible (under conditions of hierarchy for the charged leptons and without
considering the see-saw mechanism or a more elaborate extension of the SM) to
guarantee large leptonic mixing angles with any general symmetry or
transformation of only known particles. If such symmetries exist, they must be
realized in more extended scenarios.Comment: RevTeX, 4 pages, no figure
Future Oscillation Experiments and Present Data
Our goal in this paper is to examine the discovery potential of laboratory
experiments searching for the oscillation , in the light of recent data on solar and atmospheric neutrino
experiments, which we analyse together with the most restrictive results from
laboratory experiments on neutrino oscillations. In order to explain
simultaneously present results we use a four-neutrino framework, with an
additional sterile neutrino. Our predictions are rather pessimistic for the
upcoming experiments NOMAD and CHORUS, which, we find, are able to explore only
a small area of the oscillation parameter space. On the other hand, the
discovery potential of future experiments is much larger. We consider three
examples. E803, which is approved to operate in the future Fermilab main
injector beam line, MINOS, a proposed long-baseline experiment also using the
Fermilab beam, and NAUSICAA, an improved detector which improves by an order of
magnitude the performance of CHORUS/NOMAD and can be operated either at CERN or
at Fermilab beams. We find that those experiments can cover a very substantial
fraction of the oscillation parameter space, having thus a very good chance of
discovering and oscillation modes.Comment: Latex file using ReVTeX and epsifig.sty. 40 Pages. Revised version
includes new references and changed Fig.
Determination of the activity of the "5"1Cr - neutrino - source for the GALLEX-experiment
The overall procedure of the GALLEX-experiment for the measurement of solar neutrinos was checked by an artificial neutrino source consisting of the nuclide "5"1Cr. A very high activity of this nuclide was produced by neutron-activation of 35.6 kg of metallic chromium enriched in "5"0Cr to 38.6%. It decays with a halflife of 27.7 days by electron capture emitting neutrinos of comparable energy to solar neutrinos. For this check-experiment which was carried out twice, the activity of the "5"1Cr-source must be known as exactly as possible. The activity-determination was carried out independently by several groups of the GALLEX-collaboration using different methods. At FzK, two methods were applied: dissolution of samples of the irradiated chromium metal in 3 M sulfuric acid and #gamma#-spectrometry of the 320 keV line of "5"1Cr; and, after almost complete decay of the "5"1Cr, determination of "5"1V, the stable decay product of "5"1Cr, by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and by atomic absorption spectroscopy (AAS). These methods are described. The accuracy of #gamma#-spectrometry (#+-#1.5%) is somewhat better than that of atomic spectroscopy (#+-# 3.0%). According to these measurements the activity of the second source (average of "5"1Cr- and V-measurements: 70.6 Pbq) turned out to be higher than that of the first source (64.6 Pbq) by 8.5%. The results are discussed. (orig.)Available from TIB Hannover: ZA 5141(5818) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman