^{3} He Transport in the Sun and the Solar Neutrino Problem

Arxiv preprint astro-ph/9707015, 1997

The standard solar model (SSM) yield a 8 B solar neutrino flux which is consistent within the theoretical and experimental uncertainties with that observed at Super-Kamiokande. The combined results from the Super-Kamiokande and the Chlorine solar neutrino experiments do not provide a solid evidence for neutrino properties beyond the minimal standard electroweak model. The results from the Gallium experiments and independently the combined results from Super-Kamiokande and the Chlorine experiment imply that the 7 Be solar neutrino flux is strongly suppressed compared with that predicted by the SSM. This conclusion, however, is valid only if the neutrino absorption cross sections near threshold in Gallium and Chlorine do not differ significantly from their theoretical estimates. Such a departure has not been ruled out by the Chromium source experiments in Gallium. Even if the 7 Be solar neutrino flux is suppressed compared with that predicted by the SSM, still it can be due to astrophysical effects not included in the simplistic SSM. Such effects include spatial and/or temporal variations in the temperature in the solar core induced by the convective layer through g-modes or by rotational mixing in the solar core, and dense plasma effects which may strongly enhance p-capture by 7 Be relative to e-capture. The new generation of solar observations, which already look non stop deep into the sun, like Super-Kamiokande through neutrinos, and SOHO and GONG through acoustic waves, may be able to point at the correct solution; astrophysical solutions if they detect unexpected temporal and/or spatial behaviour, or particle physics solutions if Super-Kamiokande detects characteristic spectral distortion or temporal variations (e.g., the day-night effect) of the 8 B solar neutrino flux. If Super-Kamiokande will discover neither spectral distortions nor time dependence of the 8 solar neutrino flux then, only future solar neutrino experiments such as SNO, BOREXINO and HELLAZ, will be able to find out whether the solar neutrino problem is due to neutrino properties beyond the minimal standard electroweak model or whether it is just a problem of the too simplistic standard solar model.

1995

The solar neutrino problem has persisted for almost three decades. Recent results from Kamiokande, SAGE, and GALLEX indicate a pattern of neutrino fluxes that is very difficult to reconcile with plausible variations in standard solar models. This situation is reviewed and suggested particle physics solutions are discussed. A summary is given of the important physics expected from SNO, SuperKamiokande, and other future experiments.

Solar Physics, 2008

A search for any particular feature in any single solar neutrino dataset is unlikely to establish variability of the solar neutrino flux since the count rates are very low. It helps to combine datasets, and in this article we examine data from both the Homestake and GALLEX experiments. These show evidence of modulation with a frequency of 11.85 yr-1 , which could be indicative of rotational modulation originating in the solar core. We find that precisely the same frequency is prominent in power spectrum analyses of the ACRIM irradiance data for both the Homestake and GALLEX time intervals. These results suggest that the solar core is inhomogeneous and rotates with sidereal frequency 12.85 yr-1. We find, by Monte Carlo calculations, that the probability that the neutrino data would by chance match the irradiance data in this way is only 2 parts in 10,000. This rotation rate is significantly lower than that of the inner radiative zone (13.97 yr-1) as recently inferred from analysis of Super-Kamiokande data, suggesting that there may be a second, inner tachocline separating the core from the radiative zone. This opens up the possibility that there may be an inner dynamo that could produce a strong internal magnetic field and a second solar cycle.

Reports on Progress in Physics, 2011

Neutrinos are fundamental particles ubiquitous in the Universe and whose properties remain elusive despite more than 50 years of intense research activity. This review illustrates the importance of solar neutrinos in Astrophysics, Nuclear Physics, and Particle Physics. After a description of the historical context, we remind the reader of the noticeable properties of these particles and of the stakes of the solar neutrino puzzle. The Standard Solar Model triggered persistent efforts in fundamental Physics to predict the solar neutrino fluxes, and its constantly evolving predictions have been regularly compared to the detected neutrino signals. Anticipating that this standard model could not reproduce the internal solar dynamics, a Seismic Solar Model was developed which enriched theoretical neutrino flux predictions with in situ observation of acoustic and gravity waves propagating in the Sun. This seismic model contributed to the stabilization of the neutrino flux predictions. This review reminds the main historical steps, from the pioneering Homestake mine experiment and the GALLEX-SAGE experiments capturing the first pp neutrinos. It emphasizes the importance of the Superkamiokande and SNO detectors. Both experiments demonstrated that the solar-emitted electronic neutrinos are partially transformed into other neutrino flavors before reaching the Earth. This sustained experimental effort opens the door to Neutrino Astronomy, with long-base lines and underground detectors. The success of BOREXINO in detecting the 7 Be neutrino signal alone instills confidence in the physicists ability to detect each neutrino source separately. It justifies the building of a new generation of detectors to measure the entire solar neutrino spectrum with greater detail, as well as supernova neutrinos. A coherent picture emerged from neutrino physics and helioseismology. Today, new paradigms take shape in these two fields: the neutrinos are massive particles, but their masses are still unknown, and the research on the solar interior is focusing on the dynamical aspects and on signature of dark matter. The magnetic moment of the neutrino begins to be an actor of stellar evolution. The third part of the review is dedicated to this prospect. The understanding of the crucial role of both rotation and magnetism in solar physics benefit from SoHO, SDO, and PICARD space observations, and from new prototype like GOLF-NG. The magnetohydrodynamical view of the solar interior is a new way of understanding the impact of the Sun on the Earth environment and climate. For now, the particle and stellar challenges seem decoupled, but this is only a superficial appearance. The development of asteroseismology-with the COROT and KEPLER spacecrafts-and of neutrino physics will both contribute to improvements in our understanding of, for instance, supernova explosions. This shows the far-reaching impact of Neutrino and Stellar Astronomy.

Journal of High Energy Physics, 2003

We analyze all available solar and related reactor neutrino experiments, as well as simulated future 7 Be, p − p, and pep solar neutrino experiments. We treat all solar neutrino fluxes as free parameters subject to the condition that the total luminosity represented by the neutrinos equals the observed solar luminosity (the 'luminosity constraint'). Existing experiments plus the luminosity constraint show that the p − p solar neutrino flux is 1.02 ± 0.02 (1σ) times the flux predicted by the BP00 standard solar model; the 7 Be neutrino flux is 0.93 +0.25 −0.63 the predicted flux; and the 8 B flux is 1.01 ± 0.04 the predicted flux. The CNO fluxes are very poorly determined. The neutrino oscillation parameters are: ∆m 2 = 7.3 +0.4 −0.6 × 10 −5 eV 2 and tan 2 θ 12 = 0.41 ± 0.04. We evaluate how accurate future experiments must be to determine more precisely neutrino oscillation parameters and solar neutrino fluxes, and to elucidate the transition from vacuum-dominated to matter-dominated oscillations at low energies. A future 7 Be ν − e scattering experiment accurate to ±10% can reduce the uncertainty in the experimentally determined 7 Be neutrino flux by a factor of four and the uncertainty in the p − p neutrino flux by a factor of 2.5 (to ±0.8%). A future p − p experiment must be accurate to better than ±3% to shrink the uncertainty in tan 2 θ 12 by more than 15%. The idea that the Sun shines because of nuclear fusion reactions can be tested accurately by comparing the observed photon luminosity of the Sun with the luminosity inferred from measurements of solar neutrino fluxes. Based upon quantitative analyses of present and simulated future experiments, we answer the question: Why perform low-energy solar neutrino experiments?

Nuclear Physics B - Proceedings Supplements, 2001

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.

Astroparticle Physics, 2005

Although KamLAND apparently rules out Resonant-Spin-Flavor-Precession (RSFP) as an explanation of the solar neutrino deficit, the solar neutrino fluxes in the Cl and Ga experiments appear to vary with solar rotation. Added to this evidence, summarized here, a power spectrum analysis of the Super-Kamiokande data reveals significant variation in the flux matching a dominant rotation rate observed in the solar magnetic field in the same time period. Three frequency peaks, all related to this rotation rate, can be explained quantitatively. A Super-Kamiokande paper reported no time variation of the flux, but showed the same peaks, there interpreted as statistically insignificant, due to an inappropriate analysis. This modulation is small (7%) in the Super-Kamiokande energy region (and below the sensitivity of the Super-Kamiokande analysis) and is consistent with RSFP as a subdominant neutrino process in the convection zone. The data display effects that correspond to solar-cycle changes in the magnetic field, typical of the convection zone. This subdominant process requires new physics: a large neutrino transition magnetic moment and a light sterile neutrino, since an effect of this amplitude occurring in the convection zone cannot be achieved with the three known neutrinos. It does, however, resolve current problems in providing fits to all experimental estimates of the mean neutrino flux, and is compatible with the extensive evidence for solar neutrino flux variability.

Physics Letters B, 1997

The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T = 1.58 × 10 7 K, in excellent agreement with Standard Solar Models. Conservatively, we estimate that the accuracy of this determination is ∆T /T = 1.4%, better than that in SSM. Neutrino fluxes are calculated. The lower limit to the boron neutrino flux, obtained with maximum reduction factors from all sources of uncertainties, is 2σ higher than the flux measured recently by SuperKamiokande.

The Astrophysical Journal, 2008

Recent coordinated power-spectrum analyses of radiochemical solar neutrino data and the solar irradiance have revealed a highly significant, high-Q common modulation at 11.85 yr-1. Since the stability of this frequency points to an explanation in terms of rotation, this result may be attributable to non-spherically-symmetric nuclear burning in a solar core with sidereal rotation frequency 12.85 yr-1. The variability of the amplitude (on a timescale of years) suggests that the relevant nuclear burning is variable as well as asymmetric. Recent analysis of Super-Kamiokande solar neutrino data has revealed r-mode-type modulations with frequencies corresponding to a region with sidereal rotation frequency 13.97 yr-1. If this modulation is attributed to the RSFP (Resonant Spin Flavor Precession) process, it provides a measurement of the rotation rate deep in the radiative zone. These two results suggest that the core rotates significantly more slowly than the radiative zone. If one accepts an upper limit of 7 MG for the Sun's internal magnetic field, an RSFP interpretation of the Super-Kamiokande results leads to a lower limit of 10-12 Bohr magnetons for the neutrino transition magnetic moment.

Physics Letters B, 1996

arXiv:astro-ph/9509116v1 22 Sep 1995 astro-ph/9509116 LNGS-95/96 INFNFE-15-95 INFNCA-TH9511