Precise predictions of the antineutrino spectra emitted by nuclear reactors is a key ingredient in measurements of reactor neutrino oscillations as well as in recent applications to the surveillance ...of power plants in the context of nonproliferation of nuclear weapons. We report new calculations including the latest information from nuclear databases and a detailed error budget. The first part of this work is the so-called ab initio approach where the total antineutrino spectrum is built from the sum of all {beta} branches of all fission products predicted by an evolution code. Systematic effects and missing information in nuclear databases lead to final relative uncertainties in the 10-20% range. A prediction of the antineutrino spectrum associated with the fission of {sup 238}U is given based on this ab initio method. For the dominant isotopes we developed a more accurate approach combining information from nuclear databases and reference electron spectra associated with the fission of {sup 235}U, {sup 239}Pu, and {sup 241}Pu, measured at Institut Laue-Langevin (ILL) in the 1980s. We show how the anchor point of the measured total {beta} spectra can be used to suppress the uncertainty in nuclear databases while taking advantage of all the information they contain. We provide new reference antineutrino spectra for {sup 235}U, {sup 239}Pu, and {sup 241}Pu isotopes in the 2-8 MeV range. While the shapes of the spectra and their uncertainties are comparable to those of the previous analysis of the ILL data, the normalization is shifted by about +3% on average. In the perspective of the reanalysis of past experiments and direct use of these results by upcoming oscillation experiments, we discuss the various sources of errors and their correlations as well as the corrections induced by off-equilibrium effects.
We investigate the possible origins of the reactor antineutrino anomalies in norm and shape within the framework of a summation model where β^{-} transitions are simulated by a phenomenological model ...of Gamow-Teller decay strength. The general trends of divergence from the Huber-Mueller model on the antineutrino side can be reproduced in both norm and shape. From the exact electron-antineutrino correspondence of the summation model, we predict similar distortions in the electron spectra, suggesting that biases on the reference spectra of fission electrons could be the cause of the anomalies.
The Daya Bay, Double Chooz and RENO experiments recently observed a significant distortion in their detected reactor antineutrino spectra, being at odds with the current predictions. Although such a ...result suggests to revisit the current reactor antineutrino spectra modeling, an alternative scenario, which could potentially explain this anomaly, is explored in this letter. Using an appropriate statistical method, a study of the Daya Bay experiment energy scale is performed. While still being in agreement with the γ calibration data and B12 measured spectrum, it is shown that a O(1%) deviation of the energy scale reproduces the distortion observed in the Daya Bay spectrum, remaining within the quoted calibration uncertainties. Potential origins of such a deviation, which challenge the energy calibration of these detectors, are finally discussed.
The reactor antineutrino anomaly Mention, G
Journal of physics. Conference series,
01/2013, Letnik:
408, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Recently, new reactor antineutrino spectra have been provided for 235U, 239Pu, 241Pu, and 238U, increasing the mean flux by about 3 percent. To a good approximation, this reevaluation applies to all ...reactor neutrino experiments. The synthesis of published experiments at reactor-detector distances below 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-ν data disfavors the no-oscillation hypothesis at 99.8% C.L. The oscillation parameters are such that |Δm2new| > 1.5 eV2 (95%) and sin2(2θnew) = 0.14 ± 0.08 (95%).
The standard three-neutrino oscillation paradigm, associated with small squared mass splittings Delta m super(2) << 0.1 eV super(2), 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 (ProQuest: Formulae and/or non-USASCII text omitted) >> 0.01 eV super(2) and being insensitive to standard weak interactions. Precision measurements at very short baselines (5-15 m) with intense MeV nu sub(e) emitters can be used to probe these anomalies. In this article, the expected nu sub(e) signal and backgrounds of a generic experiment which consists of deploying an intense beta super(-) 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.
Core-collapse supernovae produce an intense burst of electron antineutrinos in the few-tens-of-MeV range. Several Large Liquid Scintillator-based Detectors (LLSD) are currently operated worldwide, ...being very effective for low energy antineutrino detection through the Inverse Beta Decay (IBD) process. In this article, we develop a procedure for the prompt extraction of the supernova location by revisiting the details of IBD kinematics over the broad energy range of supernova neutrinos. Combining all current scintillator-based detector, we show that one can locate a canonical supernova at 10 kpc with an accuracy of 45 degrees (68% C.L.). After the addition of the next generation of scintillator-based detectors, the accuracy could reach 12 degrees (68% C.L.), therefore reaching the performances of the large water Čerenkov neutrino detectors. We also discuss a possible improvement of the SuperNova Early Warning System (SNEWS) inter-experiment network with the implementation of a directionality information in each experiment. Finally, we discuss the possibility to constrain the neutrino energy spectrum as well as the mass of the newly born neutron star with the LLSD data.
We presented a detailed quantitative discussion of the measurement of the leptonic mixing angle θ13 through currently scheduled reactor neutrino oscillation experiments. We focussed on Double Chooz ...(Phase I & II), Daya Bay (Phase I & II) and RENO experiments. We performed a unified analysis, including systematics, backgrounds and accurate experimental setup in each case. Each identified systematical uncertainty and background impact has been assessed on experimental setups following published data when available and extrapolating from Double Chooz acquired knowledge otherwise. We sum up, here, a new common analysis of their sensitivities to sin2(2θ13) and study the impact of the different systematics based on the pulls approach. Through this generic statistical analysis we discuss the advantages and drawbacks of each experimental setup.
We present the use of a low background counting facility, equipped with a p-type 80% relative efficiency HPGe detector, protected by active and passive shielding, and large enough to count a 10
in ...photo-multiplier tube (PMT). A GEANT4 Monte-Carlo of this detector was developed and tuned to 3% accuracy. We report the U, Th, and K content in three different types of PMTs used in current neutrino experiments, with accuracies of
∼
10
ppb
for U and Th and of
∼
15
ppm
for K.
The major advances achieved over the last decades in the understanding of fundamental neutrino physics allow us to apply the detection of reactor antineutrino signals to automatic and nonintrusive ...nuclear power plant surveys. Here, we present the NUCIFER experiment, a 1-ton Gd-doped liquid scintillator detector to be installed a few 10 m from a reactor core for measurements of its thermal power and plutonium (Pu) content. The design of such a small volume detector has been focused on high detection efficiency (~ 50% and good background rejection. Detailed simulations of reactor-emitted antineutrino spectrum and detector response have been developed and used to calculate the NUCIFER sensitivity to illicit retrieval of Pu from the core. These results have been presented in October 2008 to the International Atomic Energy Agency (IAEA), which has expressed its interest in the potentialities of this detector as a new safeguard tool.
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