The solar neutrino problem

I review the solar neutrino problem and what it has taught us about the Sun and fundamental physics.     

Solutions to the solar neutrino problem

Several well known neutrino physics solutions to the solar neutrino problem are briefly reviewed and their status in the light of the latest experimental data is presented.     

New answer to the solar neutrino problem

The online version of the original article can be found at     

New answer to the solar neutrino problem

We suggest a new answer to the problem of the solar neutrinos: a neutrino-photon interaction that would cause the neutrinos to disappear before they leave the sun or make them lose energy towards detection thresholds. We calculate the available energy in the system of the centre of mass, and show that the photons may be endowed with a pseudo-cross-section in the system of the sun. Under the assumption of an absorption, made to simplify the neutrino transport calculation, the chlorine experiment yields:σ _a =1.8( _−1.0 ^+0.7 )*10⁻⁹ barn, which is close tog _β/(ℏc)=4·49^*10⁻⁹ barn. The escape probability is substantially larger for the gallium neutrinos than for the chlorine neutrinos. Thermal radiation in the core of a supernova is suppressed by electrical conductivity, therefore the neutrinos from SN1987A could escape; they interacted with the photon piston in the outer layers of the supernova and the interaction has to be a scattering. The cosmological implications of a neutrino-photon interaction are discussed; Hubble’s constant may have to be modified. The case of an elastic scattering between neutrino and photon is discussed in more detail. An erratum to this article is available at .     

SNO results and neutrino magnetic moment solution to the solar neutrino problem

We have analysed the solar neutrino data obtained from chlorine, gallium and Super-Kamiokande (SK) experiments (1258 days) and also the new results that came from Sudbury Neutrino Observatory (SNO) charge current (CC) and elastic scattering (ES) experiments considering that the solar neutrino deficit is due to the interaction of neutrino transition magnetic moment with the solar magnetic field. We have also analysed the moments of the spectrum of scattered electrons at SK. Another new feature in the analysis is that for the global analysis, we have replaced the spectrum by its centroid.     

Condensed matter effects in the solar neutrino problem

In addition to our earlier corrections to fusion cross sections, we proposed that previously overlooked condensed matter effects (CME) can help to account for the missing solar neutrino flux. There are three important CME. One is due to a reduction in collision frequency due to an exchange of kinetic and potential energies in collision processes. Another is an excluded volume effect. The third is a shadowing effect due to the presence of spectator species which do not participate in fusion. These CME become appreciable in the high densities encountered in stellar media where they significantly affect fusion rates, since the solar core plasma cannot accurately be described as a collisionless ideal gas. Contrary to Bahcall and Gould (1993), we do not violate Liouville's theorem, the Maxwellian distribution, nor thermodynamics in our proposed solution to the solar neutrino problem.     

A gut solution to the solar neutrino problem

Within the supersymmetric flipped SU(5)×U(1) model, we propose a mechanism for realization of the Voloshin-Vysotsky-Okun solution to the solar neutrino problem by attributing a large magnetic moment to the electron neutrino, as required to explain the solar neutrino data.     

Updated solution to the solar neutrino problem based on non-standard neutrino interactions

We present an updated version of the solution to the solar neutrino problem based on non-standard flavor changing neutrino interactions (FCNI) and non-universal flavor diagonal neutrino interactions (FDNI). We find a good fit not only to the total rates measured by all solar neutrino experiments but also to the day-night and seasonal variations of the event rate, as well as the recoil electron energy spectrum measured by the SuperKamiokande collaboration.     

On the axial-vector coupling constant and the solar neutrino problem

The influence of the value of g_A on the solar neutrino flux is discussed. It is shown that a more precise determination of g_A would be important to define the actual extent of the solar neutrino problem.     

Conventional nuclear physics solution of the solar neutrino problem

A basic and inherently simple alternative explanation of the solar neutrino problem is proposed based upon conventional nuclear physics. Our results for the tunneling factor, astrophysicalS-factor, and our resolution are compared with rather speculative solutions commonly attempted by accepting the customary ingredients of the standard solar model. We present a more realistic solution of nuclear Coulomb barrier tunneling together with a more precise parametric representation of the astrophysical functionS. We determineS from high-energy (>100 keV)⁷Be(p, )⁸B experimental cross-section data using the new tunneling factor. This leads to a low-energy fusion cross section that is lower than previous estimates by 26–36%, decreasing the anticipated neutrino flux close to experimentally detected values. This may resolve the missing solar neutrino flux problem.     

On vacuum oscillations solution of the solar neutrino problem

Experimental signatures of vacuum oscillations solution of the solar neutrino problem are considered. This solution predicts a strict correlation between a distortion of the neutrino energy spectrum and an amplitude of seasonal variations of the neutrino flux. The slope parameter which characterizes a distortion of the recoil electron energy spectrum in the Super-Kamiokande experiment and the seasonal asymmetry of the signal have been calculated in a wide range of oscillation parameters. The correlation of the slope and asymmetry gives crucial criteria for identification or exclusion of this solution. For the positive slope indicated by preliminary Super-Kamiokande data we predict (40 – 60) % enhancement of the seasonal variations.     

Coulomb dissociation of 8B and solar neutrino problem

We measured the cross section for Coulomb dissociation of ⁸B using a radioactive ⁸B beam of 46.5 MeV/u energy with a ²⁰⁸Pb target. The corss section for the ⁷Be(p,γ)⁸B capture reaction was deduced at E_cm = 0.6 – 1.7 MeV. The extracted astrophysical S₁₇ factors were consistent with the values measured by Vaughn et al. and Filippone et al. Possible corrections due to ⁷Be excited state population, E1 and M2 contribution, nuclear contribution and post acceleration effects are considered.