Search for neutrino oscillations at the palo verde nuclear reactors

We report on the initial results from a measurement of the antineutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a segmented gadolinium-loaded scintillation detector. We find that the antineutrino flux agrees with that predicted in the absence of oscillations excluding at 90% C.L. nu;(e)-nu;(x) oscillations with Deltam(2)>1.12x10(-3) eV(2) for maximal mixing and sin (2)2straight theta>0.21 for large Deltam(2). Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve nu(e).     

Search for neutrino oscillations at 15, 40 and 95 meters from a nuclear power reactor at Bugey

We report on high statistics measurements of neutrino energy spectra carried out at 15, 40 and 95 meters from a 2800 Megawatt reactor, using detection modules filled with ⁶Li-loaded liquid scintillator. No oscillations have been observed. Exclusion zones for oscillation parameters are deduced from the observed consistency of the spectra at the three distances. The minimum excluded values of the δm² and sin²2θ parameters are 1 × 10⁻²eV²and 2 × 10⁻² (at 90% CL), respectively.     

Search for neutrino oscillations

A search for ν_μ→ν_e and oscillations has been conducted with the AGS wide-band neutrino beam at the Brookhaven National Laboratory. We find more ν_e ( _e) interactions than were expected on the basis of the number of incident ν_e ( _e) calculated as part of the neutrino beam. The excess is about a factor two over the expectation, the statistical significance being about two and a half standard deviations for ν_e and weaker for _e.     

Search for neutrino oscillations in “Gargamelle” at SPS

The ν events collected in “Gargamelle” exposed at the CERN SPS wide band beam are reanalyzed to search for possible ν_μ → ν_e oscillations. No effect is found and an upper limit of 1.2 eV at 68% c.l. is determined for the mass parameters $\text{Δm = (m}{}_1{}^2\text{? m}{}_2{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in the case of maximum neutrino mixing. A limit on the ν_μ → ν_τ transition probability is also quoted, but the sensitivity is smaller.     

Search for neutrino oscillations today and tomorrow

Current and future experiments searching for neutrino oscillations are reviewed.     

Search for muon to electron neutrino oscillations

A search for _e and oscillations has been carried out with the CHARM II detector exposed to the CERN wide band neutrino beam. The data were collected over five years, alternating beams mainly composed of muon-neutrinos and muon-antineutrinos. The number of interactions of _e and observed is comparable with the number of events expected from flux calculations. For large squared mass differences the upper limits obtained on the mixing angle aresin ²2 < 9.4=" ·=">^–3 for oscillating to _e andsin ²2 < 4.8=" ·=">^–3 for to , at the 90% confidence level. Combining neutrino and antineutrino data the upper limit is 5.6 · 10^–3.On leave of absence from ITEP (Moscow)     

The Palo Verde reactor neutrino experiment a test for long baseline neutrino oscillations

Our collaboration has installed a long baseline neutrino oscillation experiment at the Palo Verde Nuclear Generating Station in Arizona. 12 tons of Gd loaded liquid scintillator, in a segmented detector, are used to search for oscillations at 740 m distance to three reactors. The anti-neutrino capture on the proton serves as detection reaction. The experiment is expected to reach a sensitivity of Δm² > 1.3 · 10⁻³ eV² and sin²2Θ > 0.1. Our range of sensitivity is tuned to test the ν_μ ↔ ν_e solution of the atmospheric neutrino anomaly.     

Search for exotic contributions to atmospheric neutrino oscillations

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν _μ → ν _τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10⁻²⁴ at sin(2ϑ_υ) = 0 and |Δυ| < (2.5–5) × 10⁻²⁶ at sin(2ϑ_υ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle. The text was submitted by the author in English.     

Detecting dark energy in long baseline neutrino oscillations

In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments.     

Detecting dark energy in long baseline neutrino oscillations

In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments.     

A fresh look at neutrino oscillations

We analyze the present experimental situation on neutrino oscillations in the standard weak interaction theory with three neutrinos. Sizeable oscillations ν_e ? ν_τ are compatible with, and perhaps indicated by, present data.     

Search for T-violation in neutrino oscillation with the use of muon polarization at a neutrino factory

A possibility to search for T violation in neutrino oscillation with the use of muon polarization is studied. The sensitivity to T violation is examined with various magnitudes of muon polarization as a function of muon energy and long-baseline distances.     

Experimental study of neutrino oscillations at a fission reactor

The electron-antineutrino spectrum has been measured at a position 8.75 m from the “point-like” core of the ILL ²³⁵U fission reactor, using the reaction $\text{ν}$_e + p → e⁺ + n. Positrons and neutrons were detected in coincidence by means of a low-background liquid scintillator and a ³He detector system. The observed neutron correlated positron spectrum is consistent with theoretical predictions assuming no neutrino oscillations. Upper limits for the oscillation parameter are presented.     

Search for the electron-positron decay of axions and axionlike particles at a nuclear power reactor at Bugey

A search for the decay of isoscalar penetrating particles into ane ⁺ e-pair has been performed at the nuclear power reactor Bugey 5, situated close to Lyon (France). The detector set-up, consisting of an arrangement of large-area multiwire proportional chambers, and the data analysis are described. No excess of decay events over background has been observed. For standard axions, therefrom, stringent upper limits for the branching ratio 〈Γ _a /Γ _M ^γ , averaged over the entire reactor gamma spectrum of magnetic multipolarity, have been obtained. Analysis in terms of the decay χ→e ⁺+e ^? of a more general axionlike boson χ yields new constraints for the decay constantf _χ which enhance existing laboratory limits considerably.     

A search for neutrino oscillations

We present here the final results of experiments searching for neutrino oscillations, carried out by the CHARM Collaboration. The data — taking took place in 1983. The first experiment was performed by exposing two detectors simultaneously to the CERN PS low energyv _µ beam. In the second experiment the full CHARM detector was exposed to the wide-band horn-focusedv _µ beam of the CERN SPS. Complete details of the experiments and data reduction are presented. No statistically significant signals for neutrino oscillations were observed. Our 90% CL limits in the appearance experiment (v _µ→v _e ) exclude Δm ²≧0.19 eV² for complete mixing (sin²2θ=1), and sin²2θ≧0.008 for the region Δm ²≧30 eV². These results, and the limits observed for (v _µ→v _x ) (disappearance of (v _µ), are in agreement with those of most other experiments but exclude part of the region previously reported as a possible indication ofv _µ→v _e oscillations.     

Inertial effects on neutrino oscillations

The inertial effects on neutrino oscillations induced by the acceleration and angular velocity of a reference frame are calculated. Such effects have been analyzed in the framework of the solar and atmospheric neutrino problem. Received: 19 March 1999 / Revised version: 9 July 1999 / Published online: 8 December 1999     

Search for neutrino oscillations vμ → vτ in CERN → Gran Sasso high-energy neutrino beam (the OPERA experiment)

The main purpose of the OPERA experiment is the direct observation of neutrino oscillations (v_μ → v_τ) in the v_μ beam from the CERN accelerator through the direct detection of τ leptons in nuclear emulsions at the Gran Sasso National Underground Laboratory. Some aspects of the use of the Russian PAVICOM facility for processing and analyzing the data obtained from the OPERA experiment are discussed.     

Matter effects for solar neutrino oscillations

Possible solar neutrino oscillations are reviewed in the two-neutrino case taking into account the effect of coherent forward scattering when neutrinos travel through the sun and earth. As recently pointed out by Mikheyev and Smirnov this effect can induce a large suppression of the solar ν_e flux for values of Δm ² around 10^?4–10^?8 eV² even for small values of the mixing angle. It also may cause substantial modifications of the solar neutrino spectrum shape. All this may be used for determining Δm ² and sin² 2θ in a large domain from the experimental results of the chlorine, gallium, indium and heavy water detectors.