Over the last 20 years a standard neutrino oscillation framework associated with small splitting between the neutrino mass states have become well established. Beyond this model, anomalies have been ...observed at short baseline in reactor, accelerator and gallium experiments. This suggests the existence of a fourth massive neutrino, affecting experiments through oscillation with active flavours with Δm2 above 0.1 eV2. To definitively test this Δm2 region, several experiments on reactors or using neutrino or antineutrino sources are in preparation.
Neutrinos for Peace Cribier, M
Journal of physics. Conference series,
04/2015, Volume:
593, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
Open access
The fundamental knowledge on neutrinos acquired in the recent years open the possibility of applied neutrino physics. Among it the automatic and non intrusive monitoring of nuclear reactor by its ...antineutrino signal could be very valuable to IAEA in charge of the control of nuclear power plants. Several efforts worldwide have already started.
Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second-shortest baseline measurement of the reactor ...neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides a new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the International Agency for Atomic Energy to enhance the safeguards of civil nuclear reactors. Deployed at only 7.2 m away from the compact Osiris research reactor core (70 MW) operating at the Saclay research center of the French Alternative Energies and Atomic Energy Commission, the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the ~0.85m3 detector remotely operating at a shallow depth equivalent to ~12m of water and under intense background radiation conditions. Based on 145 (106) days of data with the reactor on (off), leading to the detection of an estimated 40760nu sub(e), the mean number of detected antineutrinos is 281+ or -7(stat)+ or -18(syst)nu sub(e)/day, in agreement with the prediction of 277+ or -23nu sub(e)/day. Because of the large background, no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.
We report the complete GNO solar neutrino results for the measuring periods GNO III, GNO II, and GNO I. The result for GNO III (last 15 solar runs) is 54.3−9.3+9.9(stat)±2.3(syst)SNU(1σ) or ...54.3−9.6+10.2(incl. syst) SNU (1σ) with errors combined. The GNO experiment is now terminated after altogether 58 solar exposure runs that were performed between 20 May 1998 and 9 April 2003. The combined result for GNO (I+II+III) is 62.9−5.3+5.5(stat)±2.5(syst) SNU (1σ) or 62.9−5.9+6.0 SNU (1σ) with errors combined in quadrature. Overall, gallium based solar observations at LNGS (first in GALLEX, later in GNO) lasted from 14 May 1991 through 9 April 2003. The joint result from 123 runs in GNO and GALLEX is 69.3±5.5(incl. syst) SNU (1σ). The distribution of the individual run results is consistent with the hypothesis of a neutrino flux that is constant in time. Implications from the data in particle- and astrophysics are reiterated.
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.
We report the first GNO solar neutrino results for the measuring period GNO I, 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 (1
σ) or 65.8 ±
10.7
10.2 (incl. syst.) SNU (1
σ) 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 (1
σ). A combined result from both GNO I and Gallex (I–IV) together is 74.1 ±
6.7
6.8 (incl. syst.) SNU (1
σ).
We report the GALLEX solar neutrino results for the measuring period GALLEX IV, from 14 February 1996 until 23 January 1997. Counting for the GALLEX IV runs was completed on 19 June 1997. The GALLEX ...IV result from 12 solar runs is 118.4 ± 17.8 (stat.) ± 6.6 (sys.) SNU (1
σ). The combined result for GALLEX I+II+III+IV, which comprises 65 solar runs, is 77.5 ± 6.2
+4.3
−4.7(1
σ) SNU. The GALLEX experimental program to register solar neutrinos has now been completed. In April 1998, GALLEX was succeeded by a new project, the Gallium Neutrino Observatory (GNO), with newly defined motives and goals.
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 0.979(0.029). With our new flux evaluation, this ratio shifts to 0.937(0.027), leading to a deviation from unity at 98.4% 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 99.93% C.L. The oscillation parameters are such that |Delta m_{new}^2|>1.5 eV^2 (99%) and sin^2(2\theta_{new})=0.17(0.1) (95%). Constraints on the theta13 neutrino mixing angle are revised.
We report the GALLEX solar neutrino results for the measuring period GALLEX III, the period from 12 October 1994-4 October 1995. Counting for these runs was completed on 29 March 1996. The GALLEX III ...result (14 runs) is 53.9 ± 10.6(stat.) ± 3.1 (syst.) SNU (1σ). This is 15.8 SNU below but statistically compatible with the new combined result for GALLEX (I+II+III) (53 runs), which is 69.7 ± 6.7(stat.)
−4.5
+3.9(syst.) SNU (1σ) or (69.7
−8.1
+7.8) SNU with errors quadratically added. We also give the preliminary result from our second
51Cr-source experiment: the measured detector response is 83±10% of expectation. The combined result from both GALLEX
51Cr-source experiments is 92±8% of expectation.
PDF
