Beryllium Neutrinos Research Articles

Right-polarized neutral (anti)leptons in the solar neutrino flux

The flavor structure of solar beryllium neutrinos is investigated. The possible presence of neutral (anti)leptons of the second and third generations and related (electron) antineutrinos in the solar neutrino flux is considered. The energy spectra of recoil electrons upon (anti)neutrino–electron scattering are analyzed using the standard electroweak model (SM).

On the question of the magnitude of day-night asymmetry for solar neutrinos

The effect of flavor day-night asymmetry is considered for solar neutrinos of energy about 1 MeV under the assumption that the electron-density distribution within the Earth is approximately piecewise continuous on the scale of the neutrino-oscillation length. In this approximation, the resulting asymmetry factor for beryllium neutrinos does not depend on the structure of the inner Earth’s layers or on the properties of the detector used. Its numerical estimate is on the order of −4 × 10−4, which is far beyond the reach of present-day experiments.

On the flavor composition of the solar 7Be neutrino

The flavor composition of the solar beryllium neutrino was analyzed using schemes that include the new (heavy) neutrino (ν4) at a negligible angle of mixing with the light partners νe, νμ, and ντ.

On the possibilities for studying the electromagnetic properties of monoenergetic solar neutrinos in the borexino experiments

Electroweak (EW) and electromagnetic (EM) scattering of solar beryllium neutrinos by electrons are analyzed. An analysis of the influence of the mean-square charge radius of an electron neutrino $$ r_{\nu _e } = \sqrt {\left\langle {r_{_{\nu _e } }^2 } \right\rangle } $$ on differential and total cross sections is performed. The possibility of measuring the magnetic moment of an electron neutrino (μv) on the basis of isolating its contribution to the section of the discussed processes is considered.

First results of the observation of 7Be solar neutrinos with the BOREXINO detector

The results of a direct measurement of the counting rate for solar neutrinos from the electron-capture process on 7Be, 7Be(e −, ν e )7Li(E ν = 0.862 MeV), with the low-background scintillation detector BOREXINO are presented. This is the first ever real-time observation of a signal from solar neutrinos of energy below 1 MeV. The counting rate for monoenergetic beryllium neutrinos in the BOREXINO detector proved to be 47 ± 7 (stat.) ± 12 (syst.) counts/(day × 100 t), which is in agreement with the predictions of the standard solar model and the hypothesis of neutrino oscillations in matter with parameters in the LMA region.

Scattering of solar beryllium neutrinos by electrons

The flavor of solar beryllium neutrinos is investigated. Possible presence of neutral leptons of all generations (families), related (electron) antineutrinos, and “sterile” particles in the solar beryllium neutrino flux is considered. The angular distribution and energy spectrum of electrons at beryllium neutrino scattering are analyzed within the standard electroweak model.

Lithium experiment on solar neutrinos to weight the CNO cycle

The measurement of the flux of beryllium neutrinos with the accuracy of about 10% and CNO neutrinos with the accuracy 30% will enable to find the flux of pp-neutrinos in the source with the accuracy better than 1% using the luminosity constraint. The future experiments on \nu e- scattering will enable to measure with very good accuracy the flux of beryllium and pp-neutrinos on the Earth. The ratio of the flux of pp-neutrinos on the Earth and in the source will enable to find with very good accuracy a mixing angle theta solar. Lithium detector has high sensitivity to CNO neutrinos and can find the contribution of CNO cycle to the energy generated in the Sun. This will be a stringent test of the theory of stellar evolution and combined with other experiments will provide a precise determination of the flux of pp-neutrinos in the source and a mixing angle theta solar. The work on the development of the technology of lithium experiment is now in progress.

Determination of the Beryllium neutrino flux from helioseismic data

We show that helioseismology provides information on Beryllium neutrino production in the Sun. In particular, we derive a lower limit on the Beryllium neutrino flux on earth, Φ min Be = 1 · 10 9 cm −2s −1, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar center predicted by Standard Solar Models. Moreover, we obtain an helioseismic determination of Φ Be by comparing solar model with artificially changed ν Be production with helioseismic data.

Helioseismology and solar neutrinos: an update

We review recent advances concerning helioseismology, solar models and solar neutrinos. Particularly we address the following points: i) helioseismic tests of recent SSMs; ii) predictions of the Beryllium neutrino flux based on helioseismology; iii) helioseismic tests regarding the screening of nuclear reactions in the Sun.

Helioseismic determination of Beryllium neutrinos produced in the sun

We provide a determination of the Beryllium neutrino luminosity directly by means of helioseismology, without using additional assumptions. We have constructed solar models where Beryllium neutrino, ( ν Be) production is artificially changed by varying in an arbitrary way the zero energy astrophysical S-factor S 34 for the reaction 3 He+ 4 He→ 7 Be+γ . Next we have compared the properties of such models with helioseismic determinations of photospheric helium abundance, depth of the convective zone and sound speed profile. We find that helioseismology directly confirms the production rate of ν Be as predicted by SSMs to within ±25% (1 σ error). This constraint is somehow weaker than that estimated from uncertainties of the SSM (±10%), however it relies on direct observational data.

Helioseismology and Beryllium neutrinos

We derive a lower limit on the Beryllium neutrino flux on earth, Φ(Be) min=1·10 9 cm −2 s −1, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar center predicted by Standard Solar Model (SSM) calculations. We emphasize that this abundance is the only result of SSMs needed for getting Φ(Be) min. We also derive lower bounds for the Gallium signal, G min=(91±3) SNU, and for the Chlorine signal, C min=(3.24±0.14) SNU, which are about 3 σ above their corresponding experimental values, G exp=(72±6) SNU and C exp=(2.56±0.22) SNU.

A xenon solar neutrino detector

The neutrino capture reaction by 131Xe with the threshold of 352 keV is suggested for solar neutrinos detection. The most important feature of this process is its high sensitivity to beryllium neutrinos, that contribute approximately 40% to the total capture rate predicted in the Standard Solar Model (45 SNU). The expected counting rate of the xenon detector from the main solar neutrino sources predicted by the Standard Solar Model is ≈ 1500 events/yr.

A xenon solar neutrino detector

The neutrino capture by $^{131}$Xe with a threshold at 352 keV as reaction to detect solar neutrinos is examined. The most important feature of this process is its high sensitivity to beryllium neutrinos, which contribute approximately 40% to the total capture rate (45 SNU) assuming the fluxes predicted by the Standard Solar Model.

Just-so oscillation: as just as MSW?

The long wavelength (just-so) neutrino oscillation is reconsidered as a solution to the solar neutrino problem, in the context of various solar models with different original fluxes of relevant components (boron, beryllium neutrinos etc.). In the light of the presently updated results of the four solar neutrino experiments, the data fit in this scenario substantially improves and becomes almost as good as in the MSW scenario. Surprising result of our analysis is that the best data fit is achieved when the oscillation occurs only between the two neutrino states: switching on the oscillation into third neutrino increases the χX 2 value. Namely, by considering the vacuum oscillation scenario in the three-neutrino system (4 parameters), we find out that the minimum of χX 2 is always achieved in the two parameter subspace in which actually only two neutrino states oscillate. The possible implications of this observation for the neutrino mass matrix textures are also discussed.