Search

We investigate the possible origins of the norm and shape reactor antineutrino anomalies in the framework of a summation model (SM) where $\beta^{-}$ transitions are simulated by a phenomenological Gamow-Teller $\beta$-decay strength model. The general trends of the discrepancies to the Huber-Mueller model on the antineutrino side can be reproduced both in norm and shape. From the exact electron-antineutrino correspondence of the SM model, we predict similar distortions in the electron spectra, suggesting that biases on the reference fission-electron spectra could be at the origin of the anomalies.

Several observed anomalies in neutrino oscillation data could be explained by a hypothetical fourth neutrino separated from the three standard neutrinos by a squared mass difference of a few 0.1 eV$^2$ or more. This hypothesis can be tested with MCi neutrino electron capture sources ($^{51}$Cr) or kCi antineutrino $\beta$-source ($^{144}$Ce) deployed inside or next to a large low background neutrino detector. In particular, the compact size of this source coupled with the localization of the interaction vertex lead to an oscillating pattern in event spatial (and possibly energy) distributions that would unambiguously determine neutrino mass differences and mixing angles., Comment: Proceedings of the Neutrino 2012 Conference, Kyoto, Japan, June 2012. To appear in Nuclear Physics B Proceedings Supplement

This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data.

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 normlization

It is now widely accepted that a new middle baseline disappearance reactor neutrino experiment with multiple detectors could provide a clean measurement of the $\theta_{13}$ mixing angle, free from any parameter degeneracies and correlations induced by matter effect and the unknown leptonic Dirac CP phase. The current best constraint on the third mixing angle comes from the Chooz reactor neutrino experiment $\sin^{2}(2\theta_{13})<0.2$ (90$ %$ C.L., $\Delta m_{\rm atm}^{2}=2.0 10^{-3}$ eV$^{2}$). Several projects of experiment, with different timescales, have been proposed over the last two years all around the world. Their sensitivities range from $\sin^{2}(2\theta_{13})<$ 0.01 to 0.03, having thus an excellent discovery potential of the $\nu_e$ fraction of $\nu_3$., Comment: Talk given at the 6th International Workshop on Neutrino Factories & Superbeams, July 26-Aug 1, 2004, Osaka, Japan. 5 pages

The Double-Chooz experiment goal is to search for a non-vanishing value of the Theta13 neutrino mixing angle. This is the last step to accomplish prior moving towards a new era of precision measurements in the lepton sector. The current best constraint on the third mixing angle comes from the CHOOZ reactor neutrino experiment $\sin(2\theta_{13})^{2}<0.2$ (90% C.L., $\Delta m_{atm}^{2}=2.0$ eV$^{2}$). Double-Chooz will explore the range of $\sin(2\theta_{13})^{2}$ from 0.2 to 0.03-0.02, within three years of data taking. The improvement of the CHOOZ result requires an increase in the statistics, a reduction of the systematic error below one percent, and a careful control of the backgrounds. Therefore, Double-Chooz will use two identical detectors, one at 150 m and another at 1.05 km distance from the Chooz nuclear cores. In addition, we will to use the near detector as a ``state of the art'' prototype to investigate the potential of neutrinos for monitoring the civil nuclear power plants. The plan is to start operation with two detectors in 2008, and to reach a sensitivity sin$^{2}$$(2\theta_{13})$ of 0.05 in 2009, and 0.03-0.02 in 2011., Comment: 3 pages, 1 figure, Proceedings of Nufact'04, July 26 - August 01 2004, Osaka

Tremendous progress has been achieved in neutrino oscillation physics during the last few years. However, the smallness of the $\t13$ neutrino mixing angle still remains enigmatic. The current best constraint comes from the CHOOZ reactor neutrino experiment $\s2t13 < 0.2$ (at 90% C.L., for $\adm2=2.0 10^{-3} \text{eV}^2$). We propose a new experiment on the same site, Double-CHOOZ, to explore the range of $\s2t13$ from 0.2 to 0.03, within three years of data taking. The improvement of the CHOOZ result requires an increase in the statistics, a reduction of the systematic error below one percent, and a careful control of the cosmic ray induced background. Therefore, Double-CHOOZ will use two identical detectors, one at $\sim$150 m and another at 1.05 km distance from the nuclear cores. The plan is to start data taking with two detectors in 2008, and to reach a sensitivity of 0.05 in 2009, and 0.03 in 2011., Comment: 102 pages, 9 chapters, 3 appendix. 43 figures