183 research outputs found
The Kr2Det project: Search for mass-3 state contribution |U_{e3}|^2 to the electron neutrino using a one reactor - two detector oscillation experiment at Krasnoyarsk underground site
The main physical goal of the project is to search with reactor antineutrinos
for small mixing angle oscillations in the atmospheric mass parameter region
around {\Delta}m^{2}_{atm} ~ 2.5 10^{-3} eV^2 in order to find the element
U_{e3} of the neutrino mixing matrix or to set a new more stringent constraint
(U_{e3} is the contribution of mass-3 state to the electron neutrino flavor
state). To achieve this we propose a "one reactor - two detector" experiment:
two identical antineutrino spectrometers with 50 ton liquid scintillator
targets located at ~100 m and ~1000 m from the Krasnoyarsk underground reactor
(~600 mwe). In no-oscillation case ratio of measured positron spectra of the
\bar{{\nu}_e} + p \to e^{+} + n reaction is energy independent. Deviation from
a constant value of this ratio is the oscillation signature. In this scheme
results do not depend on the exact knowledge of the reactor power, nu_e
spectra, burn up effects, target volumes and, which is important, the
backgrounds can periodically be measured during reactor OFF periods. In this
letter we present the Krasnoyarsk reactor site, give a schematic description of
the detectors, calculate the neutrino detection rates and estimate the
backgrounds. We also outline the detector monitoring and calibration
procedures, which are of a key importance. We hope that systematic
uncertainties will not accede 0.5% and the sensitivity U^{2}_{e3} ~4 10^{-3}
(at {\Delta}m^{2} = 2.5 10^{-3} eV^2) can be achieved.Comment: Latex 2e, 9 pages and 5 ps figure
Determining Neutrino Mass Hierarchy by Precision Measurements in Electron and Muon Neutrino Disappearance Experiments
Recently a new method for determining the neutrino mass hierarchy by
comparing the effective values of the atmospheric \Delta m^2 measured in the
electron neutrino disappearance channel, \Delta m^2(ee), with the one measured
in the muon neutrino disappearance channel, \Delta m^2(\mu \mu), was proposed.
If \Delta m^2(ee) is larger (smaller) than \Delta m^2(\mu \mu) the hierarchy is
of the normal (inverted) type. We re-examine this proposition in the light of
two very high precision measurements: \Delta m^2(\mu \mu) that may be
accomplished by the phase II of the Tokai-to-Kamioka (T2K) experiment, for
example, and \Delta m^2(ee) that can be envisaged using the novel Mossbauer
enhanced resonant \bar\nu_e absorption technique. Under optimistic assumptions
for the systematic uncertainties of both measurements, we estimate the
parameter region of (\theta_13, \delta) in which the mass hierarchy can be
determined. If \theta_13 is relatively large, sin^2 2\theta_13 \gsim 0.05, and
both of \Delta m^2(ee) and \Delta m^2(\mu \mu) can be measured with the
precision of \sim 0.5 % it is possible to determine the neutrino mass hierarchy
at > 95% CL for 0.3 \pi \lsim \delta \lsim 1.7 \pi for the current best fit
values of all the other oscillation parameters.Comment: 12 pages, 6 postscript figure
Nuclear Propelled Vessels and Neutrino Oscillation Experiments
We study the effect of naval nuclear reactors on the study of neutrino
oscillations. We find that the presence of naval reactors at unknown locations
and times may limit the accuracy of future very long baseline reactor-based
neutrino oscillation experiments. At the same time we argue that a nuclear
powered surface ship such as a large Russian ice-breaker may provide an ideal
source for precision experiments. While the relatively low reactor power would
in this case require a larger detector, the source could be conveniently
located at essentially any distance from a detector built at an underground
location near a shore in a region of the world far away from other nuclear
installations. The variable baseline would allow for a precise measurement of
backgrounds and greatly reduced systematics from reactor flux and detector
efficiency. In addition, once the oscillation measurement is completed, the
detector could perform geological neutrino and astrophysical measurements with
minimal reactor background.Comment: 4 pages, 2 figure
Weak and Magnetic Inelastic Scattering of Antineutrinos on Atomic Electrons
Neutrino scattering on electrons is considered as a tool for laboratory
searches of the neutrino magnetic moment. We study inelastic
-scattering on electrons bound in the germanium (Z=32) and iodine
(Z=53) atoms for antineutrinos generated in a nuclear reactor core and also in
the Sr-Y and Pm artificial sources. Using the
relativistic Hartree-Fock-Dirac model, we calculate both the magnetic and weak
scattering cross sections for the recoil electron energy range of 1 to 100 keV
where a higher sensitivity to the neutrino magnetic moment could be achieved.
Particular attention is paid to the approximate procedure which allows us to
take into account the effects of atomic binding on the inelastic scattering
spectra in a simple way.Comment: 7 pages in LaTeX, 10 figures in P
Inelastic Scattering of Tritium-Source Antineutrinos on Electrons of Germanium Atoms
Processes of the inelastic magnetic and weak scattering of
tritium-beta-source antineutrinos on the bound electrons of a germanium atom
are considered. The results obtained by calculating the spectra and cross
sections are presented for the energy-transfer range between 1 eV and 18 keV.Comment: Latex, 7 pages, 8 ps figure
On Possibilities of Studying of Supernova Neutrinos at BAKSAN
We consider the possibilities of studying a supernova collapse neutrino burst
at Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy
of Sciences) using the prposed 5-kt target-mass liquid scintillation
spectrometer. Attention is given to the influence of mixing angle
on the expected rates and spectra of neutrino events
Neutrino oscillations and uncertainty relations
We show that coherent flavor neutrino states are produced (and detected) due
to the momentum-coordinate Heisenberg uncertainty relation. The Mandelstam-Tamm
time-energy uncertainty relation requires non-stationary neutrino states for
oscillations to happen and determines the time interval (propagation length)
which is necessary for that. We compare different approaches to neutrino
oscillations which are based on different physical assumptions but lead to the
same expression for the neutrino transition probability in standard neutrino
oscillation experiments. We show that a Moessbauer neutrino experiment could
allow to distinguish different approaches and we present arguments in favor of
the 163Ho-163Dy system for such an experiment.Comment: Some small changes in section 2, results unchanged. Added referenc
Initial Results from the CHOOZ Long Baseline Reactor Neutrino Oscillation Experiment
Initial results are presented from CHOOZ, a long-baseline reactor-neutrino
vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid
scintillation calorimeter located at a distance of about 1 km. The detector was
constructed in a tunnel protected from cosmic rays by a 300 MWE rock
overburden. This massive shielding strongly reduced potentially troublesome
backgrounds due to cosmic-ray muons, leading to a background rate of about one
event per day, more than an order of magnitude smaller than the observed
neutrino signal. From the statistical agreement between detected and expected
neutrino event rates, we find (at 90% confidence level) no evidence for
neutrino oscillations in the electron antineutrino disappearance mode for the
parameter region given approximately by deltam**2 > 0.9 10**(-3) eV**2 for
maximum mixing and (sin(2 theta)**2) > 0.18 for large deltam**2.Comment: 13 pages, Latex, submitted to Physics Letters
Limits on Neutrino Oscillations from the CHOOZ Experiment
We present new results based on the entire CHOOZ data sample. We find (at 90%
confidence level) no evidence for neutrino oscillations in the anti_nue
disappearance mode, for the parameter region given by approximately Delta m**2
> 7 x 10**-4 eV^2 for maximum mixing, and sin**2(2 theta) = 0.10 for large
Delta m**2. Lower sensitivity results, based only on the comparison of the
positron spectra from the two different-distance nuclear reactors, are also
presented; these are independent of the absolute normalization of the anti_nue
flux, the cross section, the number of target protons and the detector
efficiencies.Comment: 19 pages, 11 figures, Latex fil
Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station
This final article about the CHOOZ experiment presents a complete description
of the electron antineutrino source and detector, the calibration methods and
stability checks, the event reconstruction procedures and the Monte Carlo
simulation. The data analysis, systematic effects and the methods used to reach
our conclusions are fully discussed. Some new remarks are presented on the
deduction of the confidence limits and on the correct treatment of systematic
errors.Comment: 41 pages, 59 figures, Latex file, accepted for publication by
Eur.Phys.J.
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