Solar Neutrino Physics Research Articles

Model-independent Approach of the JUNO 8B Solar Neutrino Program

The physics potential of detecting 8B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model-independent manner by using three distinct channels of the charged current (CC), neutral current (NC), and elastic scattering (ES) interactions. Due to the largest-ever mass of 13C nuclei in the liquid scintillator detectors and the expected low background level, 8B solar neutrinos are observable in the CC and NC interactions on 13C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC, and ES channels to guarantee the observation of the 8B solar neutrinos. From the sensitivity studies performed in this work, we show that JUNO, with 10 yr of data, can reach the 1σ precision levels of 5%, 8%, and 20% for the 8B neutrino flux, sin2θ12 , and Δm212 , respectively. Probing the details of both solar physics and neutrino physics would be unique and helpful. In addition, when combined with the Sudbury Neutrino Observatory measurement, the world's best precision of 3% is expected for the measurement of the 8B neutrino flux.

The potential to probe solar neutrino physics with LiCl water solution

A solar neutrino detector relying on the charged-current (CC) interaction of nu _e on mathrm{{}^{7}Li} is attractive. The total CC interaction cross-section weighted by the solar ^8B electron neutrino spectrum is approximately 60 times that of the neutrino-electron elastic scattering process. The final state effective kinetic energy after the CC interaction on mathrm{{}^{7}Li} directly reflects the neutrino energy, which stands in sharp contrast to the plateau structure of recoil electrons of the elastic scattering. The recent measurement of the optical properties of saturated LiCl water solution, especially the long attenuation length, has once again aroused our interest in LiCl. In this work, with new B(GT) experimental measurements, the CC cross-section on mathrm{{}^{7}Li} is reevaluated to be 3.759times 10^{-42}~textrm{cm}^2. Given the high solubility of LiCl of 74.5 g/100 g water at 10 ^circ C and the high natural abundance of 92.41% of mathrm{{}^{7}Li}, a solar neutrino detection proposal is made. The detector with high concentration LiCl water solution has a comparable CC event rate of nu _e on mathrm{{}^{7}Li} with that of neutrino-electron elastic scattering. The contained mathrm{{}^{35}Cl}, mathrm{{}^{6}Li}, and H also make a delayed-coincidence detection for {{bar{nu }}}_e possible. The advantages of studying the upturn effect of solar neutrino oscillation, light sterile neutrinos, and Earth matter effect are investigated in detail. The sensitivities in discovering solar neutrino upturn and light sterile neutrinos are presented.

Ab initio investigations of A=8 nuclei: α–α scattering, deformation in 8He, radiative capture of protons on 7Be and 7Li and the X17 boson

We apply the No-Core Shell Model with Continuum (NCSMC) that is capable of describing both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. The NCSMC can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We discuss applications of NCSMC to the α–α scattering and the structure of 8Be, the p+7Be and p+7Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments. The 7Be(p, γ)8B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations. We also highlight our investigation of the neutron rich exotic 8He that has been recently studied experimentally at TRIUMF with an unexpected deformation reported.

Natural Convection and Transport of Background Contamination in the Borexino Neutrino Detector

Abstract The Borexino detector at Gran Sasso National Laboratories (INFN) has obtained extraordinary achievements for solar neutrino and geoneutrino physics during its lifetime. More recently, Borexino has provided the first experimental evidence of the subdominant CNO solar neutrino flux, thanks to an outstanding low background level obtained by means of intense purification campaigns and a continuous improvement of the detector thermal stabilization over the years. In particular, this impressive thermal steadiness has led to a progressive mitigation of the internal convective currents which are responsible for the continuous background contamination of the detector sensitive inner volume. To this purpose, numerical analyses are essential to better comprehend the detector fluid dynamics, the background behavior, and are also important to propose effective countermeasures to further reduce natural convection inside the detector. In this framework, the present work investigates the flow characteristics of the liquid scintillator by means of computational fluid dynamics analyses. In particular, a full 3D model of the Borexino inner vessel is considered in the simulations, addressing the complex nature of the natural convective currents under consideration both in transient and stationary conditions. The calculated flow pattern has been adopted to predict the transport behavior of 210Po, that is fundamental for the independent constraint of 210Bi, the main background constituent affecting CNO measurement. The convection-diffusion analysis demonstrates the applicability of the adopted methodology showing a good agreement between calculation and experimental data.

The LUNA-MV facility at Gran Sasso

About 25 year ago LUNA (laboratory for Underground Nuclear Astrophysics) opened the era of underground nuclear astrophysics installing a home-made 50 kV ion accelerator under the Gran Sasso mountain. A second machine, with a terminal voltage of 400 kV, was then installed and it is still in operation. Most of the processes so far investigated were connected to the physics of solar neutrinos and hence to the hydrogen burning phase in stars. The interest in next and warmers stages of star evolution (i.e. helium and carbon burning) pushed a new project based on an ion accelerator in the MV range called LUNA-MV. Thanks to a special grant of the Italian Ministry of Research (MIUR), INFN is now building, inside one of the major halls at Gran Sasso, a new facility which will host a 3.5 MV single-ended accelerator able to deliver proton, helium and carbon beams with intensity in the mA range.

Solar Neutrino Results and Future Opportunities with Borexino

The Borexino experiment, located in the Laboratori Nazionali del Gran Sasso in Italy and widely known for its rich Solar Neutrino physics program, has recently celebrated the 10 years of data taking. Among the achievements of the Borexino experiment solar program are: a precision measurement of 7Be neutrino flux with uncertainty of 3%, limit on its day/night asymmetry, first spectral measurement of pp-neutrinos, first evidence of monoenergetic pep neutrinos at 5 sigma, 8B neutrinos detection with the lowest visible energy threshold of 3 MeV, observation of season modulation of the 7Be solar neutrino rate at 3.8 sigma and the best current limit on CNO neutrino flux.Borexino is now in its high-purity Phase II data taking, thanks to intense purification campaigns of scintillator in 2010-11 that were very successful in further reducing the already low backgrounds. The advanced tecniques of data analysis were improved, allowing to maximize the signal/noise ratio. The detector was thermally insulated in order to improve the fluid stability. As an outcome, quality of the data has significantly increased leading to new levels of sensitivity to all solar neutrino fluxes. This allows a more sensitive probe for CNO neutrinos relevant to the solar metallicity problem.

Solar neutrino physics on the beginning of 2017

Solar neutrino physics on the beginning of 2017

Physics prospects of the Jinping neutrino experiment**Supported by the National Natural Science Foundation of China (11235006, 11475093, 11135009, 11375065, 11505301, and 11620101004), the Tsinghua University Initiative Scientific Research Program (20121088035, 20131089288, and 20151080432), the Key Laboratory of Particle & Radiation Imaging (Tsinghua University), the CAS Center for Excellence in Particle Physics (CCEPP), U.S. National Science Foundation Grant PHY-1404311 (Beacom), and

The China Jinping Underground Laboratory (CJPL), which has the lowest cosmic-ray muon flux and the lowest reactor neutrino flux of any laboratory, is ideal to carry out low-energy neutrino experiments. With two detectors and a total fiducial mass of 2000 tons for solar neutrino physics (equivalently, 3000 tons for geo-neutrino and supernova neutrino physics), the Jinping neutrino experiment will have the potential to identify the neutrinos from the CNO fusion cycles of the Sun, to cover the transition phase for the solar neutrino oscillation from vacuum to matter mixing, and to measure the geo-neutrino flux, including the Th/U ratio. These goals can be fulfilled with mature existing techniques. Efforts on increasing the target mass with multi-modular neutrino detectors and on developing the slow liquid scintillator will increase the Jinping discovery potential in the study of solar neutrinos, geo-neutrinos, supernova neutrinos, and dark matter.

Borexino’s search for low-energy neutrino and antineutrino signals correlated with gamma-ray bursts

A search for neutrino and antineutrino events correlated with 2350 gamma-ray bursts (GRBs) is performed with Borexino data collected between December 2007 and November 2015. No statistically significant excess over background is observed. We look for electron antineutrinos (ν¯e) that inverse beta decay on protons with energies from 1.8 MeV to 15 MeV and set the best limit on the neutrino fluence from GRBs below 8 MeV. The signals from neutrinos and antineutrinos from GRBs that scatter on electrons are also searched for, a detection channel made possible by the particularly radio-pure scintillator of Borexino. We obtain currently the best limits on the neutrino fluence of all flavors and species below 7 MeV. Finally, time correlations between GRBs and bursts of events are investigated. Our analysis combines two semi-independent data acquisition systems for the first time: the primary Borexino readout optimized for solar neutrino physics up to a few MeV, and a fast waveform digitizer system tuned for events above 1 MeV.

New neutrino source for the study of solar neutrino physics in the vacuum-matter transition region

Production of a neutrino source through proton induced reaction is studied by using the particle transport code, GEANT4. Unstable isotope such as $^{27}$Si can be produced when $^{27}$Al target is bombarded by 15 MeV energetic proton beams. Through the beta decay process of the unstable isotope, a new electron-neutrino source in the 1.0 $\sim$ 5.0 MeV energy range is obtained. Proton induced reactions are simulated with JENDL High Energy File 2007 (JENDL/HE-2007) data and other nuclear data. For radioactive decay processes, we use "G4RadioactiveDecay" model based on the Evaluated Nuclear Structure Data File (ENSDF). We suggest target systems required for future's solar neutrino experiments, in particular, for the vacuum-matter transition region. As for the detection system of the new neutrino source, we evaluate reaction rates for available radiochemical detectors and LENA type scintillator detector. Possibility of detecting sterile neutrinos is also discussed.

CNO and pep solar neutrino measurements and perspectives in Borexino

The detection of neutrinos emitted in the CNO reactions in the Sun is one of the ambitious goals of Borexino Phase-II. A measurement of CNO neutrinos would be a milestone in astrophysics, and would allow to solve serious issues in current solar models. A precise measurement of the rate of neutrinos from the pep reaction would allow to investigate neutrino oscillations in the MSW transition region. The pep and CNO solar neutrino physics, the measurement in Borexino Phase-I and the perspectives for the new phase are reviewed in this proceeding.

Achievements in solar neutrino physics with the Borexino detector

AbstractBorexino is an organic liquid scintillator detector located in the Gran Sasso National Laboratory in central Italy. It has been designed for real‐time spectroscopy of low energy solar neutrinos. In Phase I of the experiment lasting for three years, between May 2007 and May 2010, the Collaboration performed the first independent measurements of 7Be, 8B, and pep solar neutrino fluxes. After a dedicated purification campaign of the liquid scintillator in 2011, Borexino entered into Phase II which allowed to investigate the seasonal modulation in the 7Be signal. In 2014, Borexino provided the first direct real time measurement of pp neutrinos accomplishing the whole pp‐cycle that powers the Sun. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Solar neutrino physics with low-threshold dark matter detectors

Dark matter detectors will soon be sensitive to Solar neutrinos via two distinct channels: coherent neutrino-nucleus scattering and neutrino electron elastic scattering. We establish an analysis method for extracting Solar model properties and neutrino properties from these measurements, including the possible effects of sterile neutrinos which have been hinted at by some reactor experiments and cosmological measurements. Even including sterile neutrinos, through the coherent scattering channel a 1 ton-year exposure with a low-threshold Germanium detector could improve on the current measurement of the normalization of the $^8$B Solar neutrino flux down to 3% or less. Combining with the elastic scattering data will provide constraints on both the high and low energy survival probability, and will improve on the uncertainty on the active-to-sterile mixing angle by a factor of two. This sensitivity to active-to-sterile transitions is competitive and complementary to forthcoming dedicated short baseline sterile neutrino searches with nuclear decays.

Solar neutrinos: experimental review and prospectives

Solar neutrino physics, after the golden age which led to the discovery of neutrino oscillations, is about to enter the precision era. We summarise here the current experimental knowledge in the field and the future perspectives, showing that solar neutrino detectors are and will remain in the near future a fundamental tool for a deeper understanding of stars, neutrinos, and fundamental physics.

The Borexino scintillator and solvent procurement

The Borexino experiment for solar neutrino physics and other rare phenomena requires an extremely low radioactive background to disentangle the very few events due to neutrino interactions. Therefore, the Borexino scintillator has to satisfy the most stringent radiopurity requirements, being about eight orders of magnitude less radioactive than an ordinary material. This was achieved by means of scintillator purification techniques and of a special care during all the production, handling and procurement of the scintillator solvent. This paper describes the methodology and the quality control procedures that were employed during the production, handling and shipping of the solvent.

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.

ADVANCEMENTS IN SOLAR NEUTRINO PHYSICS

We review the results of solar neutrino physics, with particular attention to the data obtained and the analyses performed in the last decades, which were determinant to solve the solar neutrino problem (SNP), proving that neutrinos are massive and oscillating particles and contributing to refine the solar models. We also discuss the perspectives of the presently running experiments in this sector and of the ones planned for the near future and the impact they can have on elementary particle physics and astrophysics.

Measurements of 8B Solar Neutrinos – Results and Prospects from SNO and SuperKamiokande

Measurements of 8 B solar neutrinos at the Sudbury Neutrino Observatory (SNO) and at SuperKamiokande (SK) result in a model independent proof that electron neutrinos born in the Sun undergo active flavor transformation. Large mixing angle, matter enhanced neutrino oscillations are responsible for this flavor transformation and the total flux of 8 B solar neutrinos measured is in agreement with standard solar model predictions. The long-standing solar neutrino problem is resolved. In this paper the salient results from measurements of 8 B solar neutrinos at SNO and SK are summarized, including recent analyses looking for potential temporal variations in the solar neutrino fluxes and a new limit on the hep solar neutrino flux. The field of solar neutrino physics has entered a new era of precision with measurements aimed at the elucidation of fundamental neutrino properties and our basic understanding of how the Sun shines. Future goals and prospects of the SNO and SK experiments are discussed.

Solar neutrino experiments: Status and prospects

Solar neutrino experiments were originally conceived as a way to demonstrate that nuclear reactions are responsible for energy generation in stars. When solar neutrinos were first detected the measured flux was much less than what solar models predicted. The Solar Neutrino Problem thus came to be and it persisted for over thirty years. It is now known that the deficit in solar neutrinos (of electron neutrino flavour) was due to neutrino oscillations and that matter effects are important. Solar neutrino experiments played a key part in these discoveries and in recent developments in neutrino physics. This report summarizes Pontecorvo Neutrino Physics School lectures that explored the physics of solar neutrinos and the experiments that detected them. The lectures also included a look forward to future solar neutrino experiments and their physics goals and these are also discussed here.

Low energy neutrino physics at Super-Kamiokande

In spite of intensive studies of solar 8B neutrinos – which resulted in the first evidence that the flavour of solar neutrinos oscillates – the characteristic, expected transition between vacuum oscillations below and matter-dominated oscillations above 3 MeV remains thus far elusive. Also, the only direct demonstration of matter effects on solar neutrino oscillations, the day/night asymmetry, has not been observed yet. After a review of past measurements, Super-Kamiokande's future solar and supernova neutrino physics sensitivity is discussed, in particular in light of the possibility of Gadolinium doping.