Electron neutrinos aresunlightconductnuclear fusionA product of the reaction from this sourceneutrinobe calledSolar neutrino。At present, the largest neutrino crossing the earth is the solar neutrino.
86% of solar neutrinos are produced through this reaction.Standard solar modelSolar neutrinos in（Proton proton chain reaction）Partial, deuterium will interact with anotherprotonResulting from integrationHelium 3 atom(He) andGamma ray, this reaction can be written as:
The isotope helium 4 atom (He) can be produced by the aforementioned He reaction:
When helium 3 and helium 4 exist in the same system,berylliumIt can be generated through fusion:
There are currently four protons and three protonsneutronBeryllium can have two different reaction pathways.The first is to capture an electron and generateLithium 7 atomAnd an electron neutrino:
This reaction produces 14% of solar neutrinos.The resulting lithium 7 will fuse with the proton to produce two helium 4 atoms.
The second reaction path is to capture a proton (numerous in stars) and generateBoron 8 atom：
The boron 8 atom will penetrateBeta (+) decayConvert toBeryllium 8 atoms, and releasepositronAnd electron neutrinos:
This reaction produces about 0.02% of the solar neutrinos, although a small number, but its energy is high.
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Solar neutrinofluxIt is directly derived from proton proton chain reaction, and has low energy, up to 400keV。There are several other production mechanisms that result in neutrino energies as high as 18 MeV.The neutrino flux on the earth is about 7.10 particles/centimeter/second。
pass throughStandard solar modelThe number of neutrinos can be predicted, but the number of electron neutrinos actually measured is only 1/3 of the predicted value, which issolar neutrino problem 。Subsequent solutions includeNeutrino oscillationAnd pointed out that neutrinos can change itstaste。staySudbury Neutrino ObservatoryAfter measuring the total flux of various types of solar neutrinos, the correctness of this concept is confirmed, and it is confirmed that neutrinos have mass.
The solar model can also predict the energy spectrum of solar neutrinos.Energy spectrum is a key information in research because different neutrino detection experiments have their own energy ranges with high detection sensitivity.Homstick experimentUse chlorine instead ofBeryllium isotopeThe solar neutrinos produced by Be decay reaction are most sensitive;Sudbury Neutrino ObservatoryThe equipment ofBoron isotopeNeutrino produced by B reaction is the most sensitive;Gallium detectors are most sensitive to neutrinos produced by proton proton chain reactions.
In 2012, calledBorexinoThe joint research plan of, reported the results of the detection of low-energy neutrinos, which originated from the proton electron proton reaction (English: Proton electron proton, PEP; seeProton proton chain reaction）Every 400 deuterons in the sun will produce one low-energy neutrino.The detector of this plan uses 100 metric tons of liquid, and three detection events occur on average every day (becauseCarbon 11 generation）, the origin is relatively rareThermonuclear reaction。
Neutrinos can trigger nuclear reactions.Ancient ore veins of different ages are exposed to neutrinos of different degrees, and the time scale is as long asGeologic AgeMeter;By observing these veins, we can study the sunluminosityChange in time.according toStandard solar modelThe solar luminosity changes with time.[1]
