Discrimination of pp solar neutrinos and^(14)C double pile-up events in a large-scale LS detector

As a unique probe,the precision measurement of pp solar neutrinos is important for studying the sun’s energy mechanism as it enables monitoring the thermodynamic equilibrium and studying neutrino oscillations in the vacuum-dominated region.For a large-scale liquid scintillator detector,a bottleneck for pp solar neutrino detection is the pile-up events of intrinsic14C decay.This paper presents a few approaches to discriminating between pp solar neutrinos and ^(14)C pile-up events by considering the differences in their time and spatial distributions.In this study,a Geant4-based Monte Carlo simulation is conducted.Multivariate analysis and deep learning technology are adopted to investigate the capability of ^(14)C pile-up reduction.The BDTG (boosted decision trees with gradient boosting) model and VGG network demonstrate good performance in discriminating pp solar neutrinos and ^(14)C double pile-up events.Under the ^(14)C concentration assumption of 5×10-18g/g,the signal significance can achieve 10.3 and 15.6 using the statistics of only one day.In this case,the signal efficiency for discrimination using the BDTG model while rejecting 99.18% ^(14)C double pile-up events is 51.1%,and that for the case where the VGG network is used while rejecting 99.81%of the ^(14)C double pile-up events is 42.7%.

Solving the Solar Neutrino Problem

A new theoretical prediction that a plasma can produce antineutrinos is used to solve the solar neutrino problem. The difference between electron-positron induced fusion, and inertial fusion experiments that have been unsuccessful so far as commercial fusion reactors is also discussed.

Quasi-Biennial Modulation of the Solar Neutrino Flux: A “Telescope” for the Solar Interior

An oscillating magnetic field deep within the solar radiative region can significantly alter the helioseismic g-modes. The presence of density gradients along g-modes, can excite Alfvén waves resonantly, the resulting waveforms show sharp spikes in the density profile at radii comparable with the neutrino’s resonant oscillation length. This process should explain the observed quasi-biennial modulation of the solar neutrino flux. If confirmed, the coupling between solar neutrino flux and g-modes should be used as a “telescope” for the solar interior.

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.

Computation of ~7Be solar neutrino flux

Within the target range from 0 to 0.1217 times the solar radius, the probability of 7Be existing as an ion with one or two bound electrons is calculated, which is turned out to be about 4.69 %, and about 95.31 % 7Be nucleus is completely ionized. After considering the influence of that portion of incompletely ionized 7Be, the renewly calculative result shows that the solar neutrino flux of 7Be will decrease from 45 000 m-2s-1 to 43 000 m-2s-1, and the predicted value of the 8B solar neutrino flux will increase from 515 m-2s-1 to 535 m-2s-1.

Effect of solar electron temperature on pep solar neutrino flux in the chlorine solar neutrino experiment and the gallium solar neutrino experiment

The rate of the electron-capture reaction of proton, p + e ?+ p → 2 H + νe, is calculated considering the temperature of solar electron in the solar center instead of that of solar ion. When the solar electron temperature is two times higher than the solar ion temperature in the solar center, the capture rate pep solar neutrino predicted by the standard solar model (SSM) is decreased to (0.16±0.01) SNU from (0.22±0.01) SNU in the chlorine solar neutrino experiment, and decreased to 2.19 SNU from 3.0 SNU in the gallium solar neutrino experiment.

The Particular Lines in the Solar Neutrino Energy Spectrum

In this paper, much attention is given to lines of minimum and maximum neutrino energies. Tritium chain of the hydrogen cycle in the Sun including reactions of 3He(e-,νe)3H(p,γ)4 is considered. At the distance of 1 a.u., the flux of tritium neutrinos is equal to 8.1 × 104 cm-2·s-1. It is an order of magnitude higher than the flux of the (hep)-neutrinos. Radial distribution of 3H-neutrinos yield inside the Sun and their energy spectrum which has a form of line at the energy of (2.5 - 3.0) keV are calculated. The flux of thermal tritium neutrinos is accompanied by a very weak flux of antineutrinos (~103 cm-2·year-1) with energy lower than 18.6 keV. These antineutrinos are produced during Urca processes 3He3H. The flux of the neutrinos of maximum possible energy (line 19.8 MeV) produced due to the (heep)-reaction (related to the (hep)-process) is estimated.

Solar neutrino background in high-pressure gaseous ^(82)SeF_(6) TPC neutrinoless double beta decay experiments

In this study,the possibility of observing a solar neutrino background in a future neutrinoless double beta decay experiment using a high-pressure gaseous ^(82)SeF_(6) TPC is investigated.Various contributions are simulated,and possible features that could be used for event classification are discussed;two types of backgrounds are identified.The rate of multi-site background events is approximately 0.63 events/(ton·yr)in a 30 keV ROI window.This background could be effectively reduced to less than 0.0001 events/(ton·yr)(95%C.L.)while maintaining a high signal efficiency of 93%by applying a selection based on the number of clusters and energy of the leading cluster.The rate of the single-electron background events is approximately 0.01 events/(ton·yr)in the ROI.Assuming a reduction factor of 10 for the single-electron background events obtained via the algorithms developed for radioactive background rejection,the total background induced by the solar neutrino would be 0.001 events/(ton·yr),which is sufficiently small for conducting ton-level experiments.

Feasibility and physics potential of detecting ^(8)B solar neutrinos at JUNO

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^(238)U and^(232)Th in the liquid scintillator can be controlled to 10^(-17)g/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.IfDelta m^(2)_(21)=4.8times10^(-5);(7.5times10^(-5))eV^(2),JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^2_(21)using^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 Delta m^2_(21)reported by solar neutrino experiments and the KamLAND experiment.

Detection of low energy solar neutrinos by a two-phase cryogenic e-bubble detector

A new two-phase cryogenic neutrino detector using electron bubble (e-bubble) specifically in liquid helium is proposed and being developed for real time, high rate measurements of low-energy p-p reac- tion neutrinos from the sun. The e-bubble detector is a time projection chamber-like (TPC) tracking detector. The task of such a neutrino detector is to detect the ionization of the elastically scattered target electrons by incident neutrinos, and then to characterize their energy and direction and to dis- tinguish them from radioactive backgrounds. The ionization signals are expected to be small and hence undergo avalanche amplification in the saturated vapor above the liquid phase by gas electron multi- pliers (GEMs) at high gain. Higher granularity and intrinsically suppressed ion feedback give a good spatial resolution and are the major advantages of this technology. It should be possible to construct such a detector to track charged particles down to 100―200 keV in a massive liquid helium target with fractional millimeter spatial resolution in three-dimensional space, using the GEM-based TPC with a high-resolution CCD camera, for both the electronic and light readout.

The Radioactivity of Nuclei &Solar Oscillations: New Experiments

The experimental detection of the hidden periodicities in the activity of various radioactive sources which were observed by different instruments and which coincided with the period of the free oscillations of the Sun gave an impetus to the further research. The simultaneous recording of gamma rays from two radioactive sources revealed the elements of synchronism and the periods of solar oscillations as well as the phase delay for the different sources in the obtained time series. A neutrino detector has been designed and tested, the advanced schemes for neutrino detection are developed, and the impact of the neutrino source on the radioactive matter is explored. The search for the new principles for creating the emitters of neutrino beams is conducted.

Rethinking the Earth in the Solar System

The recent discovery that the Earth is retarding each year by a fraction of a second its revolution around the Sun led to investigations and speculations about the cause of such a defect in what was thought to be a perfect clock. The emission of thermal radiation by the Sun cannot justify this discrepancy even if a fraction of unknown dark matter is added to increase the Sun mass loss. The increase of distance of Earth/Moon center of mass from the Sun is estimated of the order of one centimeter per year. However experimental measurements suggest values of the order from 5 to 15 centimeters, hard to be measured for the distances involved. To solve this problem, sophisticated orbital analysis has been proposed, changes in the gravitational constant G have been suggested and more precise mass/distance measurements in the solar system, asteroids included, have been requested. The present paper shows how the use of an elementary model for the Earth/Moon orbit together with a new theory for the gravitational constant G, coherent with Newton law, can solve this problem. The comprehension of gravity, the ultimate unexplained force of the universe, is the key to solve this and the many remaining question marks in the books of physics.

掺Yb^(3+)闪烁晶体的研究进展

掺Yb3+闪烁晶体是新近发展起来的一类闪烁体,有可能用于探测太阳中微子.本文简要介绍了掺Yb3+闪烁晶体的电荷迁移发光的机理以及基质晶体对温度猝灭与浓度猝灭的影响.综述了具有石榴石结构和钙钛矿结构的两类掺Yb3+闪烁晶体的研究进展,特别是Yb:YAG和Yb:YAP晶体的生长、闪烁性能以及应用前景.最后,对掺Yb3+闪烁晶体的未来研究方向做了展望.

2002年诺贝尔物理奖的启示

本文论述2002年诺贝尔物理奖获得者,R.Davis在探测太阳中微子丢失的成就;M.Koshiba在证实存在太阳中微子丢失,探测超新星中微子和大气μ中微子丢失以及证明μ中微子振荡的成就。此外,本文还叙述2002年诺贝尔物理奖给我们的启示。

太阳中心^8B中微子的产生

研究了８ Ｂ中微子产生过程中存在时间振荡的动力学判据． Ｈｏｍ ｅｓｔａｋｅ 实验记录的太阳中微子流具有时间周期性，而 Ｓｕｐｅｒ Ｋａｍ ｉｏｋａｎｄｅ 实验观测的太阳中微子流基本上是恒定的．

太阳中微子问题及其可能的解释

介绍了 2个太阳中微子问题和解决太阳中微子问题的几种可能解释 ,并详细讨论了太阳中微子振荡方案 .如果采用小混合角 (SMA)方案 ,那么 ,这 2种味的中微子的质量之差不超过 2 .32 378× 1 0 -3 eV ;如果用真空振荡 (VAC)方案 ,那么 ,这 2种味的中微子的质量之差不超过 8.94 42× 1 0 -6eV .认为如果中微子是暗物质的候选者 ,且中微子的静止质量要大于 1eV ,那么 2种中微子质量之差至多为 2 .7× 1 0 -6eV .

中微子振荡与太阳中微子问题

认为太阳中微子问题主要是标准太阳模型没有考虑 7Be( 3He,p) 9B核反应道的竞争 ,并且在计算 7Be中微子和 pep中微子时 ,并没有考虑到太阳电子温度与离子温度的差异 .如果考虑了这种差异 ,则太阳中微子问题可以得到很好地解决 。

De Broglie-Ross模型和太阳中微子问题

基于已知的 Ｄｅ Ｂｒｏｇｌｉｅ模型和 Ｒｏｓｓ模型结合的太阳中微子新模型，可以获得两个中微子合成一个光子及其能量公式。由此能解释太阳中微子的下列三个观察结果；仅检测到理论预测值的三分之一；太阳活动和中微子流间存在反相关关系并与观察到的光子释放率一致。

~3He核反应扩散系统的稳定性与太阳中微子的产生

用非平衡态动力学方法 ,研究了太阳的重力场对其内部核反应扩散系统的影响 ,得到了从太阳中心到 0 38太阳半径的核反应区域内 ,重力场的非均匀性将导致核反应扩散系统的非稳定性 ,失稳后所产生的新状态具有时间振荡特性 。

太阳重力场对核反应扩散系统稳定性及中微子产生的影响

分析了太阳重力场对核反应扩散系统稳定性及中微子产生的影响 .结果表明 ,太阳的重力场通过与太阳内部的扩散和对流过程相耦合影响核反应扩散系统的动力学行为 .在太阳中心 0～ 0 .3 8R⊙ 的核反应区内 ,重力场的非均匀性 ( ·g)将导致3He核反应扩散系统的非稳定性 ,失稳后的新状态具有振荡特性 .