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More than 40 years ago, neutrinos where conceived as a way to test the validity of the solar models which tell us that stars are powered by nuclear fusion reactions. The first measurement of the neutrino flux, in 1968 in the Homestake mine in South Dakota, detected only one third of the expected value, originating what has been known as the Solar Neutrino Problem. Different experiments were built in order to understand the origin of this discrepancy. Now we know that neutrinos undergo oscillation phenomenon changing their nature traveling from the core of the Sun to our detectors. In the work the 40 year long saga of the neutrino detection is presented; from the first proposals to test the solar models to last real time measurements of the low energy part of the neutrino spectrum. [ABSTRACT FROM AUTHOR]

This paper reviews solar neutrino observations giving emphasis to measurements carried out at the Gran Sasso underground laboratory. Characteristics of solar neutrinos are reported. Observations are discussed together with a recent controversy between the Solar Standard Model predictions and the helioseismology. The impact of future solar neutrino measurements and the role of the Gran Sasso laboratory are discussed. [ABSTRACT FROM AUTHOR]

Using the formalism for the effective cross-section factor Seff we calculate the thermonuclear reaction rates and neutrino fluxes for the pp-chain processes. We adopt the recent LUNA experimental data for the nuclear cross-section S-factor and we compute improved and updated solar neutrino fluxes which we compare with those previously obtained. [ABSTRACT FROM AUTHOR]

The Sudbury Neutrino Observatory (SNO) is the first experiment to measure the total flux of active, high-energy neutrinos from the sun. Results from SNO have solved the long-standing “Solar Neutrino Problem” by demonstrating that neutrinos change flavor. SNO measured the total neutrino flux with the neutral-current interaction of solar neutrinos with 1000 tonnes of D2O. In the first two phases of the experiment we detected the neutron from that interaction by capture on deuterium and capture on chlorine, respectively. In the third phase an array of 3He proportional counters was deployed in the detector. This allows a measurement of the neutral-current neutrons that is independent of the Cherenkov light detected by the PMT array. We are currently developing a unique, detailed simulation of the current pulses from the proportional-counter array that will be used to help distinguish signal and background pulses. [ABSTRACT FROM AUTHOR]

We have reconsidered the status of the large mixing angle (LMA) oscillation interpretation of the solar neutrino data in a more general framework where non-standard neutrino interactions are present. Using the latest data from all solar neutrino experiments and KamLAND we have found the existence of three LMA solutions, instead of the unique solution which holds in the absence of non-standard interactions, LMA-I. In addition to LMA-I, there is another solution with smaller value of Δm2 (LMA-0), and a new “dark-side” solution (LMA-D) with sin2 θ = 0.70. We comment on the complementary role of atmospheric, laboratory, reactor and future solar neutrino experiments in lifting the degeneracy between this three solutions. We also mention that establishing the issue of robustness of the oscillation picture in the most general case will require further experiments, such as those involving low energy solar neutrinos. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, present and future experimental techniques to search for solar neutrinos are discussed. A number of reasons to measure sub-MeV solar neutrinos in the future are presented. This opportunity offers a unique possibility to search for a new physics case, besides neutrino oscillations and mixing, which may play a sub-dominant role in the solar neutrino phenomenology, in particular below 1 MeV. On one side non-standard neutrino interactions can be probed through sub-MeV solar neutrinos; on the other, the astrophysics of the sun can be studied at the level of a few %’s. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The prototype of the Borexino solar neutrino experiment is a low counting rate detector located at the underground Gran Sasso Laboratory. The detector was designed and built to achieve ultra-purity in an organic liquid scintillator on a massive scale. A number of ancillary plants and screening facilities are needed to reach low background in the sub-MeV region. The detector and its screening facilities are briefly described in this paper. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The KamLAND collaboration has studied background requirements and purification methods needed to observe the 7Be neutrino from the sun. First we will discuss the present background situation in KamLAND where it is found that the main background components are 210Pb and 85Kr. It is then described how to purify the liquid scintillator. The present status and results on how to remove 210Pb from the liquid scintillator are discussed. Specifically, the detailed analysis of the effects of distillation and adsorption techniques are presented. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Cosmogenic 11C produced in muon showers is one of the main backgrounds for the detection of pep and CNO solar neutrinos in underground organic liquid scintillator detectors. Experimental data available for the effective cross section for 11C by muons indicate that 11C is in fact the dominant background for the observation of such neutrinos. 11C decays are expected to total a rate 2.5 (20) times higher than the combined rate of pep and CNO neutrinos in Borexino (KamLAND) in the energy window preferred for the pep measurement, between 0.8 and 1.3 MeV. Background from 11C in organic liquid scintillator detectors can be reduced if a neutron is emitted when the 11C nuclide is created. 11C decays can be tagged on a one-by-one basis using a three-fold coincidence with the parent muon track and the subsequent neutron capture on protons. The efficiency of such background reduction critically relies on the emission of a free neutron associated with 11C production. In order to verify the hypothesis, first suggested by Deutsch, that a neutron is in fact always emitted when 11C is produced, we perform a detailed ab initio calculation of the production of cosmogenic 11C, taking into consideration all relevant production channels. Results of the calculation are compared with the effective cross sections measured by target experiments in muon beams. “Bilnd” channels without a neutron in the final state account for only about 5% of 11C production modes. An estimation of the effectiveness of the one-by-one tagging of 11C events, in light of such “blind” channels is performed for KamLAND, Borexino, and a possible scintillator experiment at SNOLab. Both KamLAND and Borexino can significantly improve their pep and CNO solar neutrino signal and could perform a 3% mesurement of the pep solar neutrino flux in five years. At SNOLab depths the muon flux is low enough that 11C background would be much smaller than the pep and CNO neutrino signal and hence negligible. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The enhancement factor to the thermonuclear reaction rate in the center of the Sun is calculated using the Feynman-Kac path integral of the grand-canonical partition function. Using the generalized virial expansion for a multicomponent quantum plasma, we have calculated the truncated pair distribution function for solar conditions up to the order ρ5/2 in density. The enhancement factor is calculated for the p - p channel. This result extends the well-known Salpeter calculation of the enhancement factor in the classical limit and exhibits the various classical and quantum corrections beyond the Debye-Hückel screening correction. In this issue, it comes out that quantum corrective terms related to the statistics are the leading corrections beyond the Salpeter’s result. Indeed, this result can induce significant changes in the prediction of solar neutrino deficit. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The solar neutrino problem has puzzled physicists for 30 years. There were two beautiful results announced in 2002 that solved this problem. The SNO experiment measured the solar neutrino flux via both charged current and neutral current interactions which gave strong evidence for flavor transitions of neutrinos on their way between the sun and the earth. In late 2002, KamLAND provided confirmation for this solar neutrino solution independent of any solar neutrino results. It measured the flux and the energy spectrum of anti-neutrinos coming from nuclear reactors and provided the first evidence for anti-neutrino disappearance. Assuming CPT invariance, the LMA region is the only solar neutrino solution consistent with KamLAND. I focus my discussion here on KamLAND results and prospects. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Solar Neutrinos from the decay of [SUP8]B have been detected at the Sudbury Neutrino Observatory (SNO) by charged current (CC) and neutral current (NC) interactions on deuterium and elastic scattering (ES) of electrons. The SNO data indicate that with the assumption of undistorted [SUP8]B shape, the flux for ν[SUBe] is φ[SUBe] = 1.76[SUP+0.05,SUB-0.05] (stat.)[SUP+0.09,SUB-0.09] (syst.) × 10[SUP6] cm[SUP-2]s[SUP-1] for a kinetic energy threshold of 5 MeV. The non-ν[SUBe] Flux is φ[SUBμτ] = 3.41[SUP+0.45,SUB-0.45 (stat.)[SUP+0.48,SUB-0.45](syst.) × 10[SUP6] cm[SUP-2]s[SUP-1]. This provides strong evidence for solar ν[SUBe] flavor transformation. The day and night solar neutrino energy spectra and rates have also been measured. For CC events, the ν[SUBe] asymmetry is 14.0% ± 6.3%[SUP+1.5.SUB-1.4]%. By additionally constraining the total (NC) flux of active neutrinos to have no asymmetry, the ν[SUBe] asymmetry becomes 7.0% ± 4.9%[SUP+1.3,SUB-1.2]%. A global solar neutrino analysis strongly favors the Large Mixing Angle (LMA) solution in a two-flavor neutrino oscillation model. [ABSTRACT FROM AUTHOR]

These lectures discuss the possibilities for the origin of neutrino mass terms, as well as the evidence for masses and mixings from atmospheric and solar neutrino oscillations. The programme includes: 1.- Introduction, 2.- Dirac versus Majorana neutrinos, 3.- Effective Lagrangian approach, 4.- Absolute Neutrino Masses, 5.- Neutrino Oscillations, 6.- Atmospheric Neutrinos, 7.Solar Neutrinos, 8.- Outlook. [ABSTRACT FROM AUTHOR]

Solar neutrino oscillations as a probe for the magnetic fields and matter density fluctuations in the solar interior as well as for the neutrino electromagnetic properties are discussed. The analysis of neutrino oscillations in the framework of the neutrino spin-flavor conversion in the convective zone magnetic fields as a sub-leading effect to the main LMA MSW oscillations could give the constraints to neutrino transition magnetic moment and magnetic field amplitude. We present the sensitivity of solar neutrino oscillations to the strength of the matter density perturbations given for the current experimental data and for future KamLAND result. The likely mechanism to generate the density noise based on the resonance between helioseismic and Alfvén waves is pointed. [ABSTRACT FROM AUTHOR]

In this short lecture, I discuss some basic phenomenological aspects of CP and T violation in neutrino oscillation. Using CP/T trajectory diagrams in the bi-probability space, I try to sketch out some essential features of the interplay between the effect of CP/T violating phase and that of the matter in neutrino oscillation. [ABSTRACT FROM AUTHOR]