Solar neutrino oscillation phenomenology

This article summarises the status of the solar neutrino oscillation phenomenology at the end of 2002 in the light of the SNO and KamLAND results. We first present the allowed areas obtained from global solar analysis and demonstrate the preference of the solar data towards the large-mixing-angle (LMA) MSW solution. A clear confirmation in favour of the LMA solution comes from the KamLAND reactor neutrino data. The KamLAND spectral data in conjunction with the global solar data further narrows down the allowed LMA region and splits it into two allowed zones a low Δm ² region (low-LMA) and high Δm ² region (high-LMA). We demonstrate through a projected analysis that with an exposure of 3 kton-year (kTy) KamLAND can remove this ambiguity.     

Solving Solar Neutrino Puzzle via LMA MSW Conversion

We analyze the existing solar neutrino experiment data and show the allowed regions. The result from SNO＇s salt phase itself restricts quite a lot the allowed region＇s area. Reactor neutrinos play an important role in determining oscillation parameters. KamLAND gives decisive conclusion on the solution to the solar neutrino puzzle, in particular, the spectral distortion in the 766.3 Ty KamLAND data gives another new improvement in the constraint of solar MSW-LMA solutions. We confirm that at 99.73% C.L. the high-LMA solution is excluded.     

Antineutrino science by KamLAND

KamLAND measured the $\bar{\nu }$_e’s flux from distant nuclear reactors, and found fewer events than expected from standard assumptions about $\bar{\nu }$_e propagation at the 99.998% confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at 99.6% C.L., and prefers the distortion from neutrino oscillation effects. A two-flavor oscillation analysis of the data from KamLAND and solar neutrino experiments with CPT invariance, yields Δm2=7.9−0.5+0.6×10−5 eV² and tan2θ=0.40−0.07+0.10. All solutions to the solar neutrino problem except for the large mixing angle (LMA) region are excluded. KamLAND succeeded in detecting geoneutrinos produced by the decays of ²³⁸U and ²³²Th within the Earth. The total observed number of 4.5 to 54.2, assuming a Th/U mass concentration ratio of 3.9 is consistent with 19 predicted by geophysical models. This detection allows better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth’s overall heat budget.     

Overview on neutrinos and the Daya Bay experiment

Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differences Δm ₂₁ ² , Δm ₃₁ ² (or Δm ₃₂ ² ) and a 3 × 3 unitary matrix, containing three mixing angles θ ₁₂, θ ₂₃, θ ₁₃, and one charge-parity (CP) phase. θ ₁₂ is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ ₂₃ is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. θ ₁₃ can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the first observation of non-zero θ ₁₃ with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin²2θ ₁₃ = 0.089 ± 0.010(stat) ± 0.005(syst).     

Solar neutrino oscillation parameters after KamLAND

We explore the impact of the data from the KamLAND experiment in constraining neutrino mass and mixing angles involved in solar neutrino oscillations. In particular, we discuss the precision with which we can determine the mass squared difference Δm _⊙ ² and the mixing angle θ_⊙ from combined solar and KamLAND data. We show that the precision with which Δm _⊙ ² can be determined improves drastically with the KamLAND data, but the sensitivity of KamLAND to the mixing angle is not as good. We study the effect of enhanced statistics in KamLAND as well as reduced systematics in improving the precision. We also show the effect of the SNO salt data in improving the precision. Finally, we discuss how a dedicated reactor experiment with a baseline of 70 km can improve the θ_⊙ sensitivity by a large amount.     

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.     

Study of Diffuse Supernova Neutrino Background with Modern and Future Detectors

Basic properties of the diffuse supernova neutrino background (DSNB) are reviewed. Current DSNB studies and the limits already set on the DSNB flow by the operating detectors Super-Kamiokande, SNO, and KamLAND are discussed. Prospects of DSNB studies with future high-mass neutrino detectors, such as JUNO and Hyper-Kamiokande, are considered.     

Does the sun shine by pp or CNO fusion reactions?

We show that solar neutrino experiments set an upper limit of 7.8% (7.3% including the recent KamLAND measurements) to the fraction of energy that the Sun produces via the CNO fusion cycle, which is an order of magnitude improvement upon the previous limit. New experiments are required to detect CNO neutrinos corresponding to the 1.5% of the solar luminosity that the standard solar model predicts is generated by the CNO cycle.     

Bounds on neutrino mixing with exotic singlet neutrinos

We examine the effects of mixing induced non-diagonal light-heavy neutrino weak neutral currents on the amplitude for the process (with a=e, μ or τ). By imposing constraint that the amplitude should not exceed the perturbative unitarity limit at high energy , we obtain bounds on light-heavy neutrino mixing parameter sin² where is the mixing angle. In the case of one heavy neutrino (mass mξ) or mass degenerate heavy neutrinos, for Λ=1 TeV, no bound is obtained for mξ<0.50 TeV. However, sin² ≤3.8 × 10⁻⁶ for mξ=5 TeV and sin ≤6.0 × 10⁻⁸ for mξ=10 TeV. For Λ=∞, no constraint is obtained for mξ<0.99 TeV and sin² ≤3.8 × 10⁻² (for mξ=5 TeV) and sin² ≤9.6 × 10⁻³ (for mξ=10 TeV).     

On the possibility of detecting solar <Emphasis Type="Italic">pp</Emphasis> neutrino with the large-volume liquid organic scintillator detector

It is shown that a large-volume liquid organic scintillator detector with an energy resolution of 10 keV at 200 keV (1σ) will be sensitive to solar pp neutrinos, if operated at the target radiopurity levels for the Borexino detector or the solar neutrino project of KamLAND.     

Muon与Tau中微子的运动学有效质量及其不可探测性

利用最新的WMAP观测数据推导出电子、Muon和Tau中微子的运动学有效质量的一般上限:e2+μ2+τ2=m12+m22+m32<0.5eV2,或α<0.71eV(其中α=e,μ,τ)。考虑现有中微子振荡的实验数据,进一步得到e<0.24eV以及μ≈τ<0.24eV. 因此有效质量_μ和_τ太小而无法被探测.     

Neutrino anomaly and ν-nucleus interactions

A review of various calculations of the inclusive quasi-elastic reactions and pion production processes in neutrino reactions for various nuclei at intermediate energies relevant to solar, atmospheric and accelerator neutrinos is presented     

Quantum Mechanics of Neutrino Oscillations

We present a simple but general treatment of neutrino oscillations in the framework of quantum mechanics, using plane waves and intuitive wave packet principles when necessary. We attempt to clarify some confusing statements that have recently appeared in the literature.     

中微子振荡与中微子的静止质量

简要回顾了中微子的发现过程,论述了中微子的基本性质及三种不同类型的中微子,讨论了中微子振荡的最新实验结果及其与中微子静止质量的关系,指出了中微子的静止质量在物理学与天文学中的重要性以及确定中微子的静止质量有待进一步解决的问题。     

Atmospheric neutrinos and discovery of neutrino oscillations

Neutrino oscillation was discovered through studies of neutrinos produced by cosmic-ray interactions in the atmosphere. These neutrinos are called atmospheric neutrinos. They are produced as decay products in hadronic showers resulting from collisions of cosmic rays with nuclei in the atmosphere. Electron-neutrinos and muon-neutrinos are produced mainly by the decay chain of charged pions to muons to electrons. Atmospheric neutrino experiments observed zenith-angle and energy dependent deficit of muon-neutrino events. Neutrino oscillations between muon-neutrinos and tau-neutrinos explain these data well. Neutrino oscillations imply that neutrinos have small but non-zero masses. The small neutrino masses have profound implications to our understanding of elementary particle physics and the Universe. This article discusses the experimental discovery of neutrino oscillations.     

Comments on the determination of the neutrino mass ordering in reactor neutrino experiments

We consider the problem of determination of the neutrino mass ordering via precise study of the vacuum neutrino oscillations in the JUNO and other future medium baseline reactor neutrino experiments. We are proposing to resolve neutrino mass ordering by determination of the neutrino oscillation parameters from analysis of the data of the reactor experiments and comparison them with the oscillation parameters obtained from analysis of the solar and KamLAND experiments.     

Solar mass-varying neutrino oscillations

We propose that the solar neutrino deficit may be due to oscillations of mass-varying neutrinos (MaVaNs). This scenario elucidates solar neutrino data beautifully while remaining comfortably compatible with atmospheric neutrino and K2K data and with reactor antineutrino data at short and long baselines (from CHOOZ and KamLAND). We find that the survival probability of solar MaVaNs is independent of how the suppression of neutrino mass caused by the acceleron-matter couplings varies with density. Measurements of MeV and lower energy solar neutrinos will provide a rigorous test of the idea.     

Neutrino masses,nuclear matrix elements,and the 0<Emphasis Type="Italic">νββ</Emphasis> decay of <Superscript>76</Superscript>Ge

Neutrino data, obtained from SNO, SK, CHOOZ, KamLAND, and WMAP, are used to establish the upper limit of 〈m_ν〉 relevant for the 0νββ. The decay of ⁷⁶Ge is discussed within different light-neutrino mass spectra and with different nuclear matrix elements.     

中微子振荡实验——超出标准模型的实验检验（Ⅰ）

文章总结了中微子振荡实验在历史和现状,介绍了几个太阳中微子丢失实验的结果和几个大气μ中微子丢失实验结果,这些结果表明存在中微子振荡,即中微子具有质量,它是超出标准模型的信号,文章还介绍了21世纪初研究中微子振荡和若干重要实验,噬基线中微子振荡实验以及建造μ子贮存环来产生高能电子中微子束进行中微子振荡的实验以及测量中微子振荡时的CP破坏的设想。