782 research outputs found
Neutrinos and Non-proliferation in Europe
International audienceTriggered by the demand of the IAEA, neutrino physicists in Europe involved with the Double Chooz experiment are studying the potential of neutrino detection to monitor nuclear reactors. In particular a new set of experiments at the ILL is planned to improve the knowledge of the neutrino spectrum emitted in the fission of 235U and 239Pu
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Results of the whole GALLEX experiment
After 5.5 years of data taking, GALLEX ended its experimental phase. The solar neutrino production rate, 76.4 {+-} 8 SNU represents about 55% of the predicted rate. The As tests prove, at the 1% level, the reliability of the technique and the detection of {sup 51}Cr neutrino, with the nominal efficiency (93.0 {+-} 8%), control the response of the detector to neutrinos in the solar energy range
Chimie et neutrinos
Cet article illustre la synergie qui existe entre la chimie et la détection des neutrinos, ces particules élémentaires dont l'existence fut confirmée grâce à l'invention des détecteurs à liquide scintillant par des chimistes. Les progrès de ces détecteurs sont issus des recherches des chimistes. La résolution de l'énigme des neutrinos solaires fut rendue possible entre autres par l'obtention d'une extrême pureté radiochimique des différentes cibles utilisées
Observation of beta decay of In-115 to the first excited level of Sn-115
In the context of the LENS R&D solar neutrino project, the gamma spectrum of
a sample of metallic indium was measured using a single experimental setup of 4
HP-Ge detectors located underground at the Gran Sasso National Laboratories
(LNGS), Italy. A gamma line at the energy (497.48 +/- 0.21) keV was found that
is not present in the background spectrum and that can be identified as a gamma
quantum following the beta decay of In-115 to the first excited state of Sn-115
(9/2+ --> 3/2+). This decay channel of In-115, which is reported here for the
first time, has an extremely low Q-value, Q = (2 +/- 4) keV, and has a much
lower probability than the well-known ground state-ground state transition,
being the branching ratio b = (1.18 +/- 0.31) 10^-6. This could be the beta
decay with the lowest known Q-value. The limit on charge non-conserving beta
decay of In-115 is set at 90% C.L. as tau > 4.1 10^20 y.Comment: 19 pages, 5 figures, 2 table
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
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
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
The sign of the day-night asymmetry for solar neutrinos
A qualitative understanding of the day-night asymmetry for solar neutrinos is
provided. The greater night flux in nu_e is seen to be a consequence of the
fact that the matter effect in the sun and that in the earth have the same
sign. It is shown in the adiabatic approximation for the sun that for all
values of the mixing angle theta_V between 0 and pi/2, the night flux of
neutrinos is greater than the day flux. Only for small values of theta_V where
the adiabatic approximation badly fails does the sign of the day-night
asymmetry reverse.Comment: 3 pages, 3 figures, typos corrected and references adde
Monte Carlo evaluation of the external gamma, neutron and muon induced background sources in the CUORE experiment
CUORE is a 1 ton scale cryogenic experiment aiming at the measurement of the
Majorana mass of the electron neutrino. The detector is an array of 988 TeO2
bolometers used for a calorimetric detection of the two electrons emitted in
the BB0n of 130Te. The sensitivity of the experiment to the lowest Majorana
mass is determined by the rate of background events that can mimic a BB0n. In
this paper we investigate the contribution of external sources i.e.
environmental gammas, neutrons and cosmic ray muons to the CUORE background and
show that the shielding setup designed for CUORE guarantees a reduction of this
external background down to a level <1.0E-02 c/keV/kg/y at the Q-value, as
required by the physical goal of the experiment.Comment: 14 pages, 7 figure
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