566 research outputs found
Reanalysis of the GALLEX solar neutrino flux and source experiments
After the completion of the gallium solar neutrino experiments at the
Laboratori Nazionali del Gran Sasso (GALLEX}: 1991-1997; GNO: 1998-2003) we
have retrospectively updated the GALLEX results with the help of new technical
data that were impossible to acquire for principle reasons before the
completion of the low rate measurement phase (that is, before the end of the
GNO solar runs). Subsequent high rate experiments have allowed the calibration
of absolute internal counter efficiencies and of an advanced pulse shape
analysis for counter background discrimination. The updated overall result for
GALLEX (only) is (73.4 +7.1 -7.3) SNU. This is 5.3% below the old value of
(77.5 + 7.5 -7.8) SNU (PLB 447 (1999) 127-133) with a substantially reduced
error. A similar reduction is obtained from the reanalysis of the 51Cr neutrino
source experiments of 1994/1995.Comment: Accepted by Physics Letters B January 13, 201
Beta decay of 115-In to the first excited level of 115-Sn: Potential outcome for neutrino mass
Recent observation of beta decay of 115-In to the first excited level of
115-Sn with an extremely low Q_beta value (Q_beta ~ 1 keV) could be used to set
a limit on neutrino mass. To give restriction potentially competitive with
those extracted from experiments with 3-H (~2 eV) and 187-Re (~15 eV), atomic
mass difference between 115-In and 115-Sn and energy of the first 115-Sn level
should be remeasured with higher accuracy (possibly of the order of ~1 eV).Comment: 9 pages, 3 figures; talk at the NANP'05 Conferenc
The Reactor Antineutrino Anomaly
Recently new reactor antineutrino spectra have been provided for 235U, 239Pu,
241Pu and 238U, increasing the mean flux by about 3 percent. To good
approximation, this reevaluation applies to all reactor neutrino experiments.
The synthesis of published experiments at reactor-detector distances <100 m
leads to a ratio of observed event rate to predicted rate of 0.976(0.024). With
our new flux evaluation, this ratio shifts to 0.943(0.023), leading to a
deviation from unity at 98.6% C.L. which we call the reactor antineutrino
anomaly. The compatibility of our results with the existence of a fourth
non-standard neutrino state driving neutrino oscillations at short distances is
discussed. The combined analysis of reactor data, gallium solar neutrino
calibration experiments, and MiniBooNE-neutrino data disfavors the
no-oscillation hypothesis at 99.8% C.L. The oscillation parameters are such
that |Delta m_{new}^2|>1.5 eV^2 (95%) and sin^2(2\theta_{new})=0.14(0.08)
(95%). Constraints on the theta13 neutrino mixing angle are revised.Comment: 19 pages, 15 figures ; v2/3 include typos corrected ; v4 final
version: add 5 Rovno & 2 Savannah River results + add additional constistency
checks + add a discussion on the inverse beta decay cross section
normlizatio
Generic First Order Orientation Transition of Vortex Lattices in Type II Superconductors
First order transition of vortex lattices (VL) observed in various
superconductors with four-fold symmetry is explained microscopically by
quasi-classical Eilenberger theory combined with nonlocal London theory. This
transition is intrinsic in the generic successive VL phase transition due to
either gap or Fermi velocity anisotropies. This is also suggested by the
electronic states around vortices. Ultimate origin of this phenomenon is
attributed to some what hidden frustrations of a spontaneous symmetry broken
hexagonal VL on the underlying four-fold crystalline symmetry.Comment: 4 pages, 5 figures, some typos are correcte
Experimental Parameters for a Cerium 144 Based Intense Electron Antineutrino Generator Experiment at Very Short Baselines
The standard three-neutrino oscillation paradigm, associated with small
squared mass splittings , has been successfully built
up over the last 15 years using solar, atmospheric, long baseline accelerator
and reactor neutrino experiments. However, this well-established picture might
suffer from anomalous results reported at very short baselines in some of these
experiments. If not experimental artifacts, such results could possibly be
interpreted as the existence of at least an additional fourth sterile neutrino
species, mixing with the known active flavors with an associated mass splitting
, and being insensitive to standard weak interactions.
Precision measurements at very short baselines (5 to 15 m) with intense MeV
electronic antineutrino emitters can be used to probe these anomalies. In this
article, the expected antineutrino signal and backgrounds of a generic
experiment which consists of deploying an intense beta minus radioactive source
inside or in the vicinity of a large liquid scintillator detector are studied.
The technical challenges to perform such an experiment are identified, along
with quantifying the possible source and detector induced systematics, and
their impact on the sensitivity to the observation of neutrino oscillations at
short baselines.Comment: 21 pages, 27 figures, generated with pdflatex, accepted for
publication in Phys. Rev.
The NuMI Neutrino Beam and Potential for an Off-Axis Experiment
The Neutrinos at the Main Injector (NuMI) facility at Fermilab is under
construction and due to begin operations in late 2004. NuMI will deliver an
intense beam of variable energy 2-20 GeV directed into the Earth at
58 mrad. Several aspects of the design are reviewed, and potential limitations
to the ultimate neutrino flux are described. In addition, potential
measurements of neutrino mixing properties are described.Comment: talk given at NuFact '02, Imperial College London, proceedings to
appear in J. Phys. G, revised to add a referenc
Gamow-Teller Strengths of the Inverse-Beta Transition 176Yb --> 176Lu for Spectroscopy of Proton-Proton and other sub-MeV Solar Neutrinos
Discrete Gamow-Teller (GT) transitions, 176Yb-->176Lu at low excitation
energies have been measured via the (3He,t) reaction at 450 MeV and at 0
degrees. For 176Yb, two low-lying states are observed, setting low thresholds
Q(neutrino)=301 and 445 keV for neutrino capture. Capture rates estimated from
the measured GT strengths, the simple two-state excitation structure, and the
low Q(neutrino) in Yb--Lu indicate that Yb-based neutrino-detectors are well
suited for a direct measurement of the complete sub-MeV solar electron-neutrino
spectrum (including pp neutrinos) where definitive effects of flavor conversion
are expected
GNO Solar Neutrino Observations: Results for GNOI
We report the first GNO solar neutrino results for the measuring period GNOI,
solar exposure time May 20, 1998 till January 12, 2000. In the present
analysis, counting results for solar runs SR1 - SR19 were used till April 4,
2000. With counting completed for all but the last 3 runs (SR17 - SR19), the
GNO I result is [65.8 +10.2 -9.6 (stat.) +3.4 -3.6 (syst.)]SNU (1sigma) or
[65.8 + 10.7 -10.2 (incl. syst.)]SNU (1sigma) with errors combined. This may be
compared to the result for Gallex(I-IV), which is [77.5 +7.6 -7.8 (incl.
syst.)] SNU (1sigma). A combined result from both GNOI and Gallex(I-IV)
together is [74.1 + 6.7 -6.8 (incl. syst.)] SNU (1sigma).Comment: submitted to Physics Letters B, June 2000. PACS: 26.65. +t ; 14.60
Pq. Corresponding author: [email protected] ; [email protected]
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