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The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for 8B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting 8B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background 238U and 232Th in the liquid scintillator can be controlled to 10-17g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If Δm221= 4.8 × 10-5(7.5 × 10-5) eV, JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3σ (2σ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure Δm221using 8B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Δm221reported by solar neutrino experiments and the KamLAND experiment.

There has been scientific debate about speculations that 'neutrino-induced' radioactive decay causes apparent violations of the exponential-decay law. Sturrock and others repeatedly publish papers asserting influences by solar and cosmic neutrinos on radioactive decay measurements and therefrom draw conclusions about space science that are highly speculative. Recurrent themes in their work are claims that the solar neutrino flux reveals oscillations at a monthly rate which can be linked to solar rotation, that annual and monthly oscillations occur in radioactive decay rates or directionality of emitted radiation which can be linked to variations in solar and cosmic neutrino flux hitting Earth's surface, and that unstable radioactivity measurements can be used as a source of information about the interior of the Sun and dark matter. Radionuclide metrologists have extensively investigated and refuted their arguments. Metrological evidence shows that radioactive decay does not violate the exponential-decay law and is not a probe for variations in solar neutrino flux. In this review paper, the main arguments of Sturrock are listed and counterarguments are presented. Reference is made to earlier published work in which the evidence has been scrutinised in detail. [ABSTRACT FROM AUTHOR]

The reaction Be(p7,γ)8B plays an important role in the Sun, where it determines the high energy component of the solar neutrino spectrum. The importance of this reaction triggered several experiments over the last decades. A combined analysis of their results produces an overall consistent picture for the energy dependence of the cross section, while an inflation of the quoted uncertainties is needed to accommodate the observed discrepancy in the absolute scale of the different data sets. The origin of this discrepancy needs to be understood for a reliable estimate of the astrophysical rate of Be(p7,γ)8B and its uncertainty. In addition, there is a question about possible common systematic effects, considering that all measurements performed so far share the same experimental approach, i.e. an intense proton beam impinging on a Be7 radioactive target. A direct measurement using a radioactive Be7 ion beam on a pure hydrogen gas target has been since long envisioned as a way to improve the situation. First attempts showed the feasibility of an experiment based on the use of a recoil mass separator to collect reaction products with high efficiency, but failed to reach a useful statistical significance because of the low beam intensity. Here we present the results obtained using the intense Be7 beam available at the Tandem Accelerator Laboratory at CIRCE, University of Campania, Italy coupled to the recoil mass separator ERNA in the energy range Ecm=367 to 812 keV. Our results are compatible only with a part of previous measurements, in particular those indicating a low value of the astrophysical S-factor at zero energy S17, thus exacerbating the discrepancy between existing measurements. The analysis of our data together with the results of previous data provides an estimate S17(0)=20.0±0.8 eV⋅b, where systematic uncertainties are inflated to obtain a statistically compatible data set.

In this article we review the current state of the field of solar neutrinos, including flavor oscillations, nonstandard effects, solar models, cross section measurements, and the broad experimental program thus motivated and enabled. We describe the historical discoveries that contributed to current knowledge, and define critical open questions to be addressed in the next decade. We discuss standard solar models, including uncertainties and problems related to the solar composition, and review experimental and model solar neutrino fluxes, including future prospects. We review the state of the art of the nuclear reaction data relevant for solar fusion in the proton–proton chain and carbon–nitrogen–oxygen cycle. Finally, we review the current and future experimental programs that can address outstanding questions in this field. [ABSTRACT FROM AUTHOR]

Highlights • Reply to rebuttal and new papers by Sturrock et al. which repeat old claims. • The radon experiment at GSI is susceptible to sunshine and rainfall. • There is no evidence that solar or cosmic neutrinos induce radioactive decay. • There is no relationship between radioactive decay and solar rotation. Abstract Sturrock et al. have published a "rebuttal" to a paper by Pommé et al. who refuted their claim that variations in a radon decay experiment at the Geological Survey of Israel (GSI) can be associated with solar rotation. Sturrock et al. misinterpret the variability of the decay rates in the gamma counter to assert influences by solar and cosmic neutrinos on beta decay and draw unsubstantiated conclusions about solar dynamics. Evidence suggests that the radon measurements were susceptible to solar irradiance and rainfall, whereas there is no indication that radioactive decay is influenced by the solar neutrino flux. In this reply to the rebuttal, the arguments raised by Sturrock et al. are scrutinised. [ABSTRACT FROM AUTHOR]

Liquid xenon is one of the leading targets to search for dark matter via its elastic scattering on nuclei or electrons. Due to their low-threshold and low-background capabilities, liquid xenon detectors can also detect coherent elastic neutrino–nucleus scattering (CEνNS) or neutrino–electron scattering. In this paper, we investigate the feasibility of a compact and movable liquid xenon detector with an active target mass of O(10∼100) kg and single-electron sensitivity to detect CEνNS from anti-neutrinos from a nuclear reactor. Assuming a single- and few-electron background rate at the level achieved by the XENON10/100 experiments, we expect a 5-σ detection of CEνNS with less than 400 kg-days of exposure. We further investigate the sensitivity of such a detector to neutrino magnetic moment with neutrino electron scattering. If an electronic recoil background rate of 0.01∼0.1 events/keV/kg/day above 1 keV can be achieved with adequate shielding, a liquid xenon detector can reach a neutrino magnetic moment sensitivity of 10−11μB, which would improve upon the current most-constraining laboratory limits from the GEMMA and Borexino experiments. Additionally, such a detector would be able to probe the region compatible with a magnetic moment interpretation of the low-energy excess electronic recoil events recently reported by XENON1T.

We formulate a formalism of the neutrino state evolution as an open system in the Sun, obtained by solving a quasilinear extension of the von Neumann equation. We obtain similar predictions for the averaged neutrino survival probability measured on Earth as in the Mikheev–Smirnov–Wolfenstein (MSW) approach, differing by details inside the Sun where the quasilinear evolution predicts suppression of oscillations. We discuss the issue of energy transfer between the neutrino and the Sun and the speed of the neutrino state evolution. • Solar neutrino state evolution as an open system in the Sun. • Nonlinear, quasilinear evolution preserving requirements of quantum mechanics. • Critical instabilities of the solar neutrino nonlinear evolution. • Neutrino oscillations suppressed inside the Sun; resumed outside. • Mass state ν 2 predicted on Earth; agrees with MSW effect. [ABSTRACT FROM AUTHOR]

We investigate the prospects for measuring the coherent elastic neutrino–nucleus scattering of solar and supernova neutrinos in future NaI(Tl) dark matter detection experiments. Considering the reduced background and improved light yield of the recently developed NaI(Tl) crystals, more than 3 σ observation sensitivities of the supernova neutrino within the Milky Way are demonstrated. In the case of the solar neutrino, approximately 3 σ observations are marginal with a 1 ton NaI(Tl) experiment assuming an order of magnitude reduced background, five photoelectron thresholds, and 5-year data exposure. [ABSTRACT FROM AUTHOR]