Muon-electron universality

Weak Interactions were treated by Pais who, starting from Fermi s original theory, discussed the discovery by Lee and Yang,74 almost 5 years before, of the parity violation by weak interactions, its experimental confirmation,75 the muon-electron universality,76 the idea of an intermediate boson as a mediator of weak interaction, and the two-neutrinos question. 77... 

Secondly, one can assume for the form factor the existing experimental value 1 2 = (1.676 + 0.008) fm [3] (as seen by an electron probe), assume muon-electron universality, and then give a limit within which the QED vacuum polarization contribution is tested by these measurements. In doing this, one can see that such a QED correction is tested (at the momentum transfer implied by the experiment) to the level of 0.17% the result of this experiment represents to my knowledge one of the best direct tests, so far performed, of a vacuum polarization correction. 

Conditions in the universe almost immediately after the big bang were not favorable for the formation of electrons. At that point in time, gamma rays, photons, and neutrinos had very large amounts of energy, much more than was needed to produce electrons. Instead, conditions favored the creation of much more massive particles with large energy equivalents. Among these particles were the muon and the proton. A muon (also known as a mu meson) is a much more massive relative of the electron. It has amass of 1.870 x 10"25 g, about 2,000 times that of an electron. A proton is even heavier, with a mass of about 1.660 x 10 24 g, nearly 3,000 times that of an electron. 

The creation and ultimate fate of antimatter is one of the most puzzling and intriguing questions in all of cosmology. Scientists believe that relatively equal amounts of matter (protons, muons, and electrons) must have been formed in the first few seconds of the universe s life. There appears to he no reason that one form of matter was more likely to form than the other. 

In 1960 it was proposed by several physicists, in order to explain a number of experimental observations in a simple way, that there are two neutrinos and two antineutrinos, with somewhat different properties. It was postulated that one neutrino (y) and one antineutrino (v) have a close relation of some sort to the electron and positron, and the other neutrino (y ) and antineutrino (y ) have a similar relation to the muon and antimuon. Experimental verification of this hypothesis was obtained in 1962 by a difficult experiment carried out by a group of Columbia University and Brookhaven National Laboratory scientists. As mentioned above, Reines and Cowan had shown that a neutrino produced by a reaction involving electrons reacts with a proton to produce a neutron and an electron. In the 1962 experiment it was shown that neutrinos produced by the decomposition of muons react with protons to produce only muons, and not electrons ... 

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