This was the first example of what came to be known as anti-matter, and when an electron and a positron collide, assuming they do not scatter, they annihilate each other, producing pairs of photons in the form of gamma rays. Anderson discovered the positron in 1932,] for which he received the Nobel Prize in 1936. Initially, he thought the proton could be some sort of "positive electron", but, persuaded by Robert Oppenheimer, he suggested a new particle he called the anti-electron in 1931. Paul Dirac first identified the possibility that an electron could have a positive charge. Thomson in 1897, for which, in part, he received the Nobel prize in 1906. The electron was discovered by the British physicist J. Neutrinos have a small but non-zero mass so travel at speeds very close to that of light By the following year they reported finding two errors in the experiment a clock oscillator that was ticking too fast, and an incorrectly attached fiber optic cable. In fact, the OPERA experiment in Italy, that uses muon neutrinos generated by CERN, reported anomalies in their measurements and asked the scientific community for assistance. In September of 2011, the media published many articles about CERN claiming they had found neutrinos traveled at faster than light speed. The electron neutrino is the lightest, then the muon neutrino, then the tau neutrino, but all three masses are similar. A 2014 result gives a combined maximum mass of 0.320 ± 0.081 eV. Research, as of August 2010, indicates that the minimum mass is 0.05 eV, while the sum of the three neutrino masses must be less than 0.28 eV. Initially thought to have zero mass, and therefore travel at the speed of light, recent experiments have confirmed neutrino oscillation, which requires them to have mass. Neutrinos hardly react at all with other particles, and in fact every second about 50 trillion (50,000,000,000,000) pass harmlessly thorough your body.
Subsequently, it was found experimentally. A neutron decays into a proton and an electron, but experimenters found that momentum was not conserved, so they postulated the existence of the neutrino, in fact an anti-neutrino, to carry away the excess momentum. The existence of neutrinos was inferred from neutron decay. When they are produced in particle accelerators, they decay very quickly into lighter particles The muon and the tau are much heavier than the other leptons. Electrons and the three neutrinos are inherently stable, and thus the types we commonly see around us. All the leptons have ½ Spin, and, while neutrinos carry no charge, the other three carry identical charge of -1. Leptons are fundamental particles that do not combine into other particles. Muons and Taus are, essentially, identical to electrons except for their masses. Leptons also come in three generations Electron & Electron neutrino, Muon & Muon Neutrino, and Tau & Tau Neutrino, each with their associated anti-particle.
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