Vacuum oscillations and variations of solar neutrino rates in SuperKamiokande and Borexino

Faïd, B; Fogli, G. L.; Lisi, E.; Montanino, D.

doi:10.1016/s0927-6505(98)00038-3

Cited by 24 publications

(30 citation statements)

References 23 publications

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“…The predicted 7 Be rate for vacuum oscillations at BOREXINO is in the same range as the predictions for LMA and LOW solutions. The most striking signal for vacuum oscillations would be the observation of a large seasonal variation in the BOREXINO experiment, with a clear pattern of the monthly dependence of the observed rate [44]. There should also be a day-night effect at BOREXINO associated with this seasonal variation; the day-night asymmetry should be at most ±8% (the size and sign of this asymmetry is sensitive to the exact value of ∆m 2 considered to be within the allowed VAC islands) due to the dependence of the survival probability upon the earth-sun distance.…”

Section: Predictions For Vacuum Solutionsmentioning

confidence: 99%

Before and After: How has the SNO NC measurement changed things?

Bahcall¹,

González-García²,

Peña-Garay³

2002

J. High Energy Phys.

126

121

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We present "Before and After" global oscillation solutions, as well as predicted "Before and After" values and ranges for ten future solar neutrino observables (for BOREXINO, KamLAND, SNO, and a generic p − p neutrino detector). The "Before" case includes all solar neutrino data (and some theoretical improvements) available prior to April 20, 2002 and the "After" case includes, in addition, the new SNO data on the CC, NC, and day-night asymmetry. We have performed global analyses using the full SNO day-night energy spectrum and, alternatively, using just the SNO NC and CC rates and the day-night asymmetry. The LMA solution is the only currently allowed MSW oscillation solution at ∼ 99% CL. The LOW solution is allowed only at more than 2.5σ, SMA is now excluded at 3.7σ or 4.7σ depending upon analysis strategy, and pure sterile oscillations are excluded at more than 4.7σ. Small mixing angles are "out" (pure sterile is "way out"); MSW with large mixing angles is definitely "in." Vacuum oscillations are allowed at 3σ, but not at 2σ. Precise maximal mixing is excluded at 3.2σ for MSW solutions and at more than 2.8σ for vacuum solutions. Most of the predicted values for future observables for the BOREXINO, KamLAND, and future SNO measurements are changed only by minor amounts by the inclusion of the recent SNO data. In order to test the robustness of the allowed neutrino oscillation regions that are inferred from the measurements and the predicted values for future solar neutrino observables, we have carried out calculations using a variety of strategies for analyzing the SNO and other experimental data.

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Section: Predictions For Vacuum Solutionsmentioning

confidence: 99%

Before and After: How has the SNO NC measurement changed things?

Bahcall¹,

González-García²,

Peña-Garay³

2002

J. High Energy Phys.

126

121

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“…[49] and dσ νe /dE ′ e , dσ νx /dE ′ e are ν e − e and ν x − e (x = µ, τ ) scattering cross sections taken from Ref. [46].…”

Section: A Calculation Of the Ratesmentioning

confidence: 99%

“…Detailed analyses on the seasonal variations for 7 Be neutrinos have been performed in Refs. [49,56,39].…”

Section: Predictions For Seasonal Variationsmentioning

confidence: 99%

Erratum: Three flavor long-wavelength vacuum oscillation solution to the solar neutrino problem [Phys. Rev. D63, 013005 (2001)]

Gago¹,

Nunokawa²,

Funchal³

2001

Phys. Rev. D

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We investigate the current status of the long-wavelength vacuum oscillation solution to the solar neutrino problem and to what extent the presence of a third neutrino can affect and modify it. Assuming that the smaller mass squared difference that can induce such oscillations, ∆m 2 12 , is in the range 10 −11 − 10 −8 eV 2 and the larger one, ∆m 2 23 , in the range relevant to atmospheric neutrino observations, we analyze the most recent solar neutrino data coming from Homestake, SAGE, GALLEX, GNO and Super-Kamiokande experiments in the context of three neutrino generations. We include in our vacuum oscillation analysis the MSW effect in the Sun, which is relevant for some of the parameter space scrutinized. We have also performed, as an extreme exercise, the fit without Homestake data. While we found that the MSW effect basically does not affect the best fitted parameters, it significantly modifies the allowed parameter space for ∆m 2 12 larger than ∼ 3 × 10 −10 eV 2 , in good agreement with the result obtained by A. Friedland in the case of two generations. Although the presence of a third neutrino does not essentially improve the quality of the fit, the solar neutrino data alone can give an upper bound on θ 13 , which is constrained to be less than ∼ 60 • at 95 % C.L.

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“…Another possible explanation of this excess [6,7] is that the Hep neutrino flux might be significantly larger (about a factor [10][11][12][13][14][15][16][17][18][19][20] than the SSM prediction. The Hep flux depends on solar properties, such as the 3 He abundance and the temperature, and on S 13 , the zeroenergy astrophysical S-factor of the p + 3 He → 4 He + e + + ν reaction.…”

Section: Introductionmentioning

confidence: 98%

“…The MSW seasonal variations are weaker than the VO ones at low energies. In the case of VO, the monochromatic Be-neutrinos are expected to show the strongest seasonal variations [25][26][27]19]; on the contrary, Be-neutrinos should show very small seasonal variations in the case of MSW oscillations. Since Be-neutrinos are monochromatic, their flux shows the entire seasonal variation predicted by VO; the effect is reduced for the other fluxes due to the averaging over the different phases of neutrinos with different energies within the interval of observation, ∆E.…”

Section: Introductionmentioning

confidence: 99%

Vacuum oscillations and excess of high energy solar neutrino events observed in Superkamiokande

Berezinsky

Fiorentini

Lissia

2000

Astroparticle Physics

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The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by the vacuum oscillation solution to the Solar Neutrino Problem (SNP). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.4σ) higher than the measured one, there exists a vacuum oscillation solution to SNP that reproduces both the observed spectrum of the recoil electrons, including the high energy distortion, and the other measured neutrino rates. The most distinct signature of this solution is a semi-annual seasonal variation of the 7 Be neutrino flux with maximal amplitude. While the temporal series of the GALLEX and Homestake signals suggest that such a seasonal variation could be present, future detectors (BOREXINO, LENS and probably GNO) will be able to test it.Superkamiokande [1][2][3] has recently observed an excess of solar-neutrino events at electron energies higher than 13 MeV. This excess cannot be interpreted as a distortion of the boron neutrino spectrum due to neutrino oscillations [1][2][3][4], if one restricts oneself to those oscillation solutions that explain the observed gallium, chlorine and water-cerenkov neutrino rates.It is tempting to think that this excess is the result of low statistics or small systematic errors at the end of the boron neutrino spectrum. For example, because of very steep end of the electron spectrum, even small systematic error in electron energy (e.g., due to calibration) could enhance the number of events in the highest energy bins. One should 1 wait for future Superkamiokande data, where such possible systematic effects will be further elaborated. The data from the SNO detector, which will come in the operation soon, e.g., see Ref.[5], can shed light on this excess.Another possible explanation of this excess [6,7] is that the Hep neutrino flux might be significantly larger (about a factor 10-20) than the SSM prediction. The Hep flux depends on solar properties, such as the 3 He abundance and the temperature, and on S 13 , the zeroenergy astrophysical S-factor of the p + 3 He → 4 He + e + + ν reaction. Both SSM based [7] and model-independent [8] approaches give a robust prediction for the ratio Φ ν (Hep)/S 13 . Therefore, this scenario implies a cross-section larger by a factor 10-20 than the present calculations (for reviews see [7,9]). Such a large correction to the calculation does not seem likely, though it is not excluded. A large Hep neutrino flux remains a possible explanation of the excess. The signature of Hep neutrinos, the presence of electrons above the maximum boron neutrino energy, can be tested by the SNO experiment.The Superkamiokande collaboration noticed [1] that vacuum oscillations with large ∆m 2 explain the observed high-energy excess. However, the same Ref.[1] emphasizes that those oscillation parameters that reproduce the excess do not solve the Solar Neutrino Problem (SNP), i.e., they do not explain the global rates observed by the fou...

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Vacuum oscillations and variations of solar neutrino rates in SuperKamiokande and Borexino

Cited by 24 publications

References 23 publications

Before and After: How has the SNO NC measurement changed things?

Before and After: How has the SNO NC measurement changed things?

Erratum: Three flavor long-wavelength vacuum oscillation solution to the solar neutrino problem [Phys. Rev. D63, 013005 (2001)]

Vacuum oscillations and excess of high energy solar neutrino events observed in Superkamiokande

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