Solar neutrino problem in light of super-Kamiokande data

I discuss the status of the accepted solutions to the solar neutrino problem in light of the super-Kamiokande data.     

Matter effects in active-sterile solar neutrino oscillations

We study the matter effects for solar neutrino oscillations in a general scheme, without any constraint on the number of sterile neutrinos and the mixing matrix elements, only assuming a realistic hierarchy of neutrino squared-mass differences in which the smallest squared-mass difference is effective in solar neutrino oscillations. The validity of the analytic results is illustrated with a numerical solution of the evolution equation in the simplest case of four-neutrino mixing with the realistic matter density profile inside the Sun.     

A step toward CNO solar neutrino detection in liquid scintillators

The detection of CNO solar neutrinos in ultrapure liquid scintillator detectors is limited by the background produced by bismuth-210 nuclei that undergo β-decay to polonium-210 with a lifetime of ∼7 days. Polonium-210 nuclei are unstable and decay with a lifetime equal to ∼200 days emitting α particles that can be also detected. In this Letter, we show that the Bi-210 background can be determined by looking at the time evolution of α-decay rate of Po-210, provided that α particle detection efficiency is stable over the data acquisition period and external sources of Po-210 are negligible. A sufficient accuracy can be obtained in a relatively short time. As an example, if the initial Po-210 event rate is ∼2000 cpd/100 ton or lower, a Borexino-like detector could start discerning CNO neutrino signal from Bi-210 background in Δt∼1 yr.     

Neutrinos from CNO cycle at the present epoch of the solar neutrino research

The CNO cycle contributes only a small fraction to the energy generated in the Sun but there’s still no experimental data on exactly how small this contribution is. After the results of Borexino experiment the CNO neutrinos it is the last missing chain to compose the total picture of the energy generation of the Sun. To get precision in the evaluation of the flux of pp-neutrinos one needs to measure the flux of CNO neutrinos. Then it will be possible to address the question on the presence of still unknown (hidden) sources of solar energy and/or on the presence of sterile neutrinos. The future experimental program to measure the effect from CNO neutrinos is discussed.     

Absence of a day-night asymmetry in the Be solar neutrino rate in Borexino

We report the result of a search for a day-night asymmetry in the ⁷Be solar neutrino interaction rate in the Borexino detector at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The measured asymmetry is Adn=0.001±0.012 (stat)±0.007 (syst), in agreement with the prediction of MSW-LMA solution for neutrino oscillations. This result disfavors MSW oscillations with mixing parameters in the LOW region at more than 8.5 σ. This region is, for the first time, strongly disfavored without the use of reactor anti-neutrino data and therefore the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics.     

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 .     

The rich neutrino programme of the SNO+ experiment

The SNO+ experiment is a multi-faceted neutrino experiment re-using the existing infrastructure and detector hardware of the Sudbury Neutrino Observatory located in Vale Inco’s Creighton mine, Sudbury (ON), Canada. The main aim of this, now fully-funded, experiment is the search for neutrinoless double-beta decay, however, it has access to other, very interesting, measurements involving neutrinos, such as lower energy solar neutrinos, geo- and reactor-antineutrinos and supernova neutrinos.     

The discovery of neutrino oscillations

The Nobel Prize for physics 2015 was awarded to Takaaki Kajita and Arthur McDonald for the discovery of neutrino oscillations, showing that neutrinos have a mass. This article describes the two areas of research namely the atmospheric neutrino anomaly and the problem of missing solar neutrinos which lead to these groundbreaking discoveries.     

Physics with underwater neutrino telescopes

We give a short review of the ongoing efforts in the construction of large underwater photomultiplier arrays aiming at the detection of neutrinos of astrophysical origin.     

Solutions to the solar neutrino problem

Several well known neutrino physics solutions to the solar neutrino problem are briefly reviewed and their status in the light of the latest experimental data is presented.     

中微子振荡的发现及未来

2015年诺贝尔物理学奖授予日本物理学家·田隆章和加拿大物理学家阿瑟·麦克唐纳,奖励他们发现中微子振荡现象,从而证明中微子具有非零的静止质量。这是粒子物理学唯一具有确凿实验证据的超出标准模型的新物理现象,改变了人类对物质世界基本规律的认识。文章将回顾中微子振荡现象的发现过程,介绍太阳中微子和大气中微子振荡实验的实验结果和理论解释,以及近期反应堆和加速器中微子振荡的研究成果,并展望中微子研究的前景。     

Three flavour oscillation interpretation of neutrino data

I consider the mixing of the three active neutrino flavours and obtain the constraints on the parameters of this mixing from the solar, atmospheric and reactor neutrino data.     

New answer to the solar neutrino problem

The online version of the original article can be found at     

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.     

SNO results and neutrino magnetic moment solution to the solar neutrino problem

We have analysed the solar neutrino data obtained from chlorine, gallium and Super-Kamiokande (SK) experiments (1258 days) and also the new results that came from Sudbury Neutrino Observatory (SNO) charge current (CC) and elastic scattering (ES) experiments considering that the solar neutrino deficit is due to the interaction of neutrino transition magnetic moment with the solar magnetic field. We have also analysed the moments of the spectrum of scattered electrons at SK. Another new feature in the analysis is that for the global analysis, we have replaced the spectrum by its centroid.