12/24/2022 0 Comments Definition of neutrino![]() ![]() The Italian physicist Enrico Fermi then coined the term neutrino, which means little neutron in Italian.) Neutrinos are hard to detect because their mass, if they indeed have any, is extremely low, and they possess no electric charge a chunk of iron a few light-years thick would absorb only about half of the neutrinos that struck it. (He originally wanted to name the particle a neutron but didn't publish the suggestion, and a few years later the particle we now know as the neutron was discovered and named in print. Pauli suggested that the energy was carried away by a very small, electrically neutral particle that was not being detected. A certain amount of energy that was lost in these processes could not be accounted for. Pauli was studying certain radioactive decay processes called beta decay, processes now known to involve the decay of a neutron into a proton and an electron. ^ Alexandra Witze, "Elusive solar neutrinos spotted, detection reveals more about reaction that powers sun," Science News, 181 (5), March 10, 2012, p.A Closer Look Neutrinos were not observed until 1955, roughly a quarter of a century after the physicist Wolfgang Pauli first hypothesized their existence on theoretical grounds.^ "First Evidence of pep Solar Neutrinos by Direct Detection in Borexino" (preprint on arXiv): Phys.Bellerive, Review of solar neutrino experiments. ![]() By looking at ancient ores of various ages that have been exposed to solar neutrinos over geologic time, it may be possible to interrogate the luminosity of the Sun over time, which, according to the Standard Solar Model, has changed with time. The detector contained 100 metric tons of liquid and saw on average 3 events each day (due to carbon 11 production) from this relatively uncommon thermonuclear reaction. In 2012 the collaboration known as Borexino reported detecting low-energy neutrinos for the proton-electron-proton ( pep reaction) that produces 1 in 400 deuterium nuclei in the sun. The detectors that use gallium are most sensitive to the solar neutrinos produced by the proton-proton chain reaction process. ![]() The Sudbury Neutrino Observatory is most sensitive to solar neutrinos produced by 8B. The Homestake Experiment used chlorine and was most sensitive to solar neutrinos produced by the decay of the beryllium isotope 7Be. It is essential to know this energy spectrum because different neutrino detection experiments are sensitive to different neutrino energy ranges. The energy spectrum of solar neutrinos is also predicted by solar models. This was confirmed when the total flux of solar neutrinos of all types was measured and it agreed with the earlier predictions of expected electron neutrino flux, as seen by Sudbury Neutrino Observatory, and thus confirmed that neutrinos have mass. ![]() It led to the idea of neutrino oscillation and the fact that neutrinos can change flavour. The detected number of electron neutrinos was only 1/3 of the predicted number, and this was known as the solar neutrino problem. The number of neutrinos can be predicted by the Standard Solar Model. There are also several other significant production mechanisms, with energies up to 18 MeV. The highest flux of solar neutrinos come directly from the proton-proton interaction, and have a low energy, up to 400 keV. Or in words: 4 protons + 2 electrons = Helium + 2 electron neutrinos. The main contribution comes from the so-called proton-proton chain reaction. By far the largest fraction of neutrinos passing through the Earth are Solar neutrinos. Solar neutrinos ( proton-proton chain) in the Standard Solar ModelĮlectron neutrinos are produced in the Sun as a product of nuclear fusion. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |