Solar neutrino flux measurements by the Soviet-American gallium experiment (SAGE) for half the 22-year solar cycle

We present measurements of the solar neutrino capture rate on metallic gallium in the Soviet-American gallium experiment (SAGE) over a period of slightly more than half the 22-year solar cycle. A combined analysis of 92 runs over the twelve-year period from January 1990 until December 2001 yields a capture rate of 70.8 _?5.2 ^+5.3 (stat) _?3.2 ^+3.7 (sys) SNU for solar neutrinos with energies above 0.233 MeV. This value is slightly more than half the rate predicted by the standard solar model, 130 SNU. We present the results of new runs since April 1998 and analyze all runs combined by years, months, and bimonthly periods beginning in 1990. A simple analysis of the SAGE results together with the results of other solar neutrino experiments gives an estimate of (4.6±1.2)× 10¹⁰ neutrinos cm^?2 s^?1 for the flux of the electron pp neutrinos that reach the Earth without changing their flavor. The flux of the pp neutrinos produced in thermonuclear reactions in the Sun is estimated to be (7.6 ± 2.0) × 10¹⁰ neutrinos cm^?2 s^?1, in agreement with the value of (5.95±0.06)×10¹⁰ neutrinos cm^?2 s^?1 predicted by the standard solar model.     

Contribution of gallium experiments to the understanding of solar physics and neutrino physics

The results of gallium measurements of solar neutrino and measurements with artificial sources of neutrinos are presented. Conclusions are drawn from these results, and the potential of the SAGE experiment for studying transitions of active neutrinos to sterile states for Δm ² > 0.5 eV² and a sensitivity of a few percent to the disappearance of electron neutrinos is examined.     

Topological geometrodynamics and the solar neutrino problem

A solution of the solar neutrino problem based on certain differences between T(opological) G(eometro) D(ynamics) and the standard model of the electroweak interactions is proposed. First, TGD predicts the existence of a right-handed neutrino inert with respect to ordinary electroweak interactions. Second, the generalization of the massless Dirac equation contains terms mixing differentM ⁴ chiralities, unlike the ordinary massless Dirac equation. This and the observation of anticorrelations of the solar neutrino flux with sunspot number suggest that solar neutrinos are transformed to right-handed neutrinos on the convective zone of the Sun. Third, the compactness ofCP ₂ implies topological field quantization: space-time decomposes into regions, topological field quanta, characterized by a handful of vacuum quantum numbers. In particular, there are topological obstructions for the smooth global imbeddings of magnetic fields and the decomposition of the solar magnetic field into flux tubes is predicted. Finally, every electromagnetically neutral mass distribution is accompanied by a long-rangeZ ⁰ vacuum field. If the vacuum quantum numbers inside the flux tubes of the solar magnetic field are considerably smaller than in the normal phase, theZ ⁰ electric force becomes strong and implies Thomas precession for the spin of the lefthanded component of the neutrino. As a consequence, left-handed neutrinos are transformed to right-handed ones and the process is irreversible, since righthanded neutrinos do not couple toZ ⁰.     

Are there sterile neutrinos in the flux of solar neutrinos on the earth?

It is shown that the future SNO and Super-Kamiokande experiments, in which high energy⁸B neutrinos will be detected through the observation of CC, NC and –e elastic scattering processes, could allow to reveal in a model independent way the presence of sterile neutrinos in the flux of solar neutrinos on the earth. Lower bounds for different averaged values of the probability of transition of solar v^e'S into sterile states and for the total flux of⁸B neutrinos are derived in terms of measurable quantities. The possibilities to reveal the presence of v and/or v in the solar neutrino flux on the earth are also considered and the case of transitions of solar v^e'S only into sterile states is discussed. Some numerical results for a simple model with v–v^s mixing are given.     

First results of the observation of <Superscript>7</Superscript>Be 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.     

Nuclear Responses for Neutrinos and Mo Observatory of Neutrinos

Nuclear responses for neutrinos and neutrino studies in Mo nuclei are briefly reported. Nuclear spin-isospin responses for neutrinos are crucial for neutrino studies in nuclei. Spin-isospin responses for solar neutrinos, supernova neutrinos and neutrinos involved in double-beta decays are discussed. It is of great interest to study neutrino masses and low energy solar neutrinos. It is shown that it is possible to carry out with ¹⁰⁰Mo both spectroscopic studies of double-beta decays with the sensitivity of the order of m 0.03eV and real-time exclusive studies of the low energy solar neutrinos.     

Testing the vacuum oscillation and the MSW solutions of the solar neutrino problem

Solar model independent tests of the vacuum oscillation and MSW solutions of the solar neutrino problem are considered. Detailed predictions for time (seasonal) variations of the signals due to neutrino oscillations in vacuum are given for the future solar neutrino detectors (SNO, Super-Kamiokande, BOREXINO, HELLAZ). Results on the distortions of the spectra of ⁸B neutrinos, and of e⁻ from the reaction ν + e⁻ → ν + e⁻ induced by ⁸B neutrinos, are presented in the cases of vacuum oscillations or MSW transitions for a large number of values of the relevant parameters. The possibilities to distinguish between the vacuum oscillation, the MSW adiabatic, and the MSW nonadiabatic transitions in the future solar neutrino experiments are discussed.     

Magnetic moment solution to the solar neutrino problem,anticorrelation with sunspot activity and challenges for future experiments

The analysis of the most recent solar neutrino data in the light of the resonant spin flip flavour conversion of neutrinos in the Sun suggests the existence of two possible solutions for the solar neutrino problem, one of them associated with a neutrino flavour mass square difference of the order of 10^?8 eV² and the other of the order of 10^?5eV². The magnetic moment is in the range μ_v= (10^?12 ? 10^?11) μ_B. In the first possibility the most energetic neutrinos will have their resonance in the solar onvective zone. This indicates that the forthcoming SNO and Icarus experiments are very well placed to test this solution through the anticorrelation effect with sunspot activity that may be present in the Homestake data but still remains an open question.     

Anomalouse + e − pairs in heavy ion collisions and solar neutrinos

The production of anomalouse ⁺ e ^–pairs in heavy ion collisions and the solar neutrino puzzle are two seemingly unrelated problems of the standard model of electroweak interactions. According to the observations made at Homestake and Kamiokande, the flux of solar neutrinos is too small. Furthermore, the observations made at Homestake (neutrino-nucleon scattering) show anticorrelation of the solar neutrino flux with sunspots, unlike the observations made in Kamiokande (neutrino-electron scattering). According to the previously proposed model inspired by T(opological) G(eometro) D(ynamics), anomalouse ⁺ e ^–pairs result from the decay of the leptopion, which can be regarded as a bound state of color excited electrons. In this paper we show that the generalization of PCAC ideas leads to a prediction for the lifetime and production cross section of the leptopion in agreement with data. The model is also consistent with constraints coming from Babbha scattering and supernova physics. Leptopion exchange implies a new weak interaction between leptons at low cm energies (of the order of a few MeVs), which explains the Kamiokande-Homestake puzzle. Part of the solar neutrinos are transformed in the convective zone of the Sun to right-handed neutrinos inert with respect to ordinary electroweak interactions, but interacting with electrons via leptopion exchange so that they are observed in Kamiokande. A correct average value for the neutrino flux at Kamiokande is predicted using as input the Homestake flux, and the anticorrelation with sunspots in Kamiokande is predicted to be considerably weaker than in Homestake.     

A new three-flavor oscillation solution of the solar neutrino deficit in <Emphasis Type="Italic">R</Emphasis>-parity violating supersymmetry

We present a solution of the solar neutrino deficit using three flavors of neutrinos and R-parity non-conserving supersymmetry. In this model, in vacuum, the is massless and unmixed, mass and mixing being restricted to the - sector only, which we choose in consistency with the requirements of the atmospheric neutrino anomaly. The flavor changing and flavor diagonal neutral currents present in the model and the three-flavor picture together produce an energy dependent resonance-induced - mixing in the sun. This mixing plays a key role in the new solution to the solar neutrino problem. The best fit to the solar neutrino rates and spectrum (1258-day SK and 241-day SNO data) requires a mass square difference of eV² in vacuum between the two lightest neutrinos. This solution cannot accommodate a significant day-night effect for solar neutrinos nor CP violation in terrestrial neutrino experiments. Received: 26 December 2001 / Revised version: 16 February 2002 / Published online: 26 July 2002     

The need to measure low-energy antineutrinos (<Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">⊻</Emphasis></Subscript><0.782 MeV) from the Sun

Measurements are needed of low-energy antineutrinos generated by possible neutron decay at the core of the Sun. The measurement will test the validity of a proposal that solar luminosity, solar neutrinos, and the outpouring of H⁺ ions from the solar surface are the products of a chain of reactions triggered by neutron emission from the solar core. Inverse β decay of 87-d ³⁵S, induced by capture of low-energy antineutrinos on ³⁵Cl, is a likely candidate for this measurement.     

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.     

Solar neutrinos and a proposed level in Be

Arguments are given against the existence of a narrow 0⁺ level in ⁶Be just above the ³He+³He threshold, which has been postulated recently in order to explain the low observed flux of solar neutrinos.     

Status of the SNO experiment

The Sudbury Neutrino Observatory (SNO) is a 1-kt heavy water Cherenkov detector sensitive to the flavor content of the ⁸B neutrinos originating in the Sun. The analysis of the second phase, in which salt (NaCl) was added to the heavy water in order to increase the cross section for neutrons and therefore enhance the sensitivity to solar neutrinos, is completed. Results from 391 d of data (June 2001 until September 2003) are summarized and constraints on the neutrino mixing parameters are given. The third phase of operation has started in which ³He proportional counters have been deployed inside the D₂O. These neutral-current detectors will perform a systematically independent measurement of the Solar-neutrino flux on a event-by-event basis. SNO finishes data taking at the end of 2006 and the heavy water will be removed. A new experiment using liquid scintillator to measure the pep solar neutrinos and geoneutrinos is proposed and will be described briefly. for the SNO Collaboration The text was submitted by the author in English.     

Solar neutrinos and experiments to search for the hypothetical level in 6Be

We discuss the problem of solar neutrinos, as well as the restrictions imposed on the parameters of the hypothetical level in ⁶Be and experiments to search for new levels in nuclei with A = 6.     

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 .     

Proposal of a laser radiochemical Ga detector of solar neutrinos

The technique of laser discrimination of ⁷¹Ge β-decay events in a radiochemical detector of low energy solar neutrinos is proposed and considered. This technique is based on laser selective photoionization of single Ga atom. Preliminary experiments are presented.     

Neutrino Oscillations in Caianiello's Quantum Geometry Model

Neutrino flavor oscillations are analyzed in the framework of Quantum Geometry model proposed by Caianiello. In particular, we analyze the consequences of the model for accelerated neutrino particles that experience an effective Schwarzschild geometry modified by the existence of an upper limit on the acceleration, which implies a violation of the equivalence principle. We find a shift of quantum-mechanical phase of neutrino oscillations, which depends on the energy of neutrinos as E³. Implications on atmospheric and solar neutrinos are discussed.     

The Sudbury Neutrino Observatory: Observation of flavor change for solar neutrinos

The Sudbury Neutrino Observatory (SNO) experiment was constructed by an international scientific collaboration primarily to provide a clear determination of whether solar neutrinos change their flavor in transit from the core of the sun to the earth. The detector used 1000 tonnes of heavy water (>99.92% D2O) in an ultra‐clean location 2 km underground in INCO's Creighton mine near Sudbury, Canada to observe two separate reactions of neutrinos on deuterium. The first reaction was sensitive only to electron flavor neutrinos and the second reaction was equally sensitive to all neutrino flavors. The measurements by SNO showed clearly that the hypothesis of no neutrino flavor change was ruled out by more than 5.3 standard deviations. The observation of flavor change for neutrinos implies that they have a non‐zero mass. The measured total flux of active neutrinos from ⁸B decay in the sun was found to be in excellent agreement with the predictions of solar model calculations. This paper describes the history and scientific measurements of the SNO experiment. 2