The new Sudbury Neutrino Observatory (SNO) consists of a 1000 metric ton bottle of heavy water suspended in a larger tank of light water. The observations at Sudbury are consistent with the solar models of neutrino flux assuming that this "neutrino oscillation" is responsible for observation of neutrinos other than electron neutrinos. Recent results from the Sudbury Neutrino Observatory suggest that a fraction of the electron neutrinos produced by the sun are transformed into muon neutrinos on the way to the earth. Often referred to as the Solar Neutrino Problem, this deficiency of neutrinos has been difficult to explain. Another Japanese neutrino detector called Super Kamiokande became operational in April 1996.Īn early set of experiments with a facility called the solar neutrino telescope, measured the rate of neutrino emission from the sun at only one third of the expected flux. A new neutrino detector at Sudbury, Ontario began collecting data in October of 1999. Modern neutrino detectors at IMB in Ohio and Kamiokande in Japan detected neutrinos from Supernova 1987A. Their neutrino source was a nuclear reactor (it actually produced antineutrinos from beta decay). The first experimental observation of the neutrino interacting with matter was made by Frederick Reines, Clyde Cowan, Jr, and collaborators in 1956 at the Savannah River Plant in South Carolina. Why do we say that neutrinos are left-handed? Their interactions are usually represented in terms of Feynman diagrams. Neutrinos interact only by the weak interaction. Bahcall's modeling of the solar neutrino flux led to the prediction of about 5 x 10 6 neutrinos/cm 2s.Ī remarkable opportunity for observing neutrinos came with Supernova 1987A when the Japanese observing team detected neutrinos almost coincident with the discovery of the light from the supernova. This leads to the statement "Solar neutrinos shine down on us during the day, and shine up on us during the night!". The sun emits vast numbers of neutrinos which can pass through the earth with little or no interaction. The background temperature for neutrinos is lower than that for the microwave background (2.7K) because the neutrino transparency point came earlier. This remnant neutrino density is put at 100 per cubic centimeter at an effective temperature of 2K (Simpson). In the standard Big Bang model, the neutrinos left over from the creation of the universe are the most abundant particles in the universe. The mean free path of a neutrino in water would be on the order of 10x the distance from the Earth to the Sun. This elusive particle, with no charge and almost no mass, could penetrate vast thicknesses of material without interaction. Enrico Fermi called the particle a neutrino and developed a theory of beta decay based on it, but it was not experimentally observed until 1956. The apparent violation of conservation of energy and momentum was most easily avoided by postulating another particle. The electron neutrino (a lepton) was first postulated in 1930 by Wolfgang Pauli to explain why the electrons in beta decay were not emitted with the full reaction energy of the nuclear transition. The history of a particle that appeared to have no charge and no mass is an interesting one. Neutrinos Electron Neutrinos and Antineutrinos
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |