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No. 12: Fall 1980

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Schizophrenic Neutrinos

"As the concept of the neutrino has developed since the early 1930s, it has developed a split personality and put on weight. The neutrino is now thought to come in three varieties -- electron neutrino, muon neutrino and tau neutrino. And a number of experiments are showing hints that a neutrino has a small mass and that it can oscillate from one variety to another."

These experiments are not yet conclusive; and if the neutrino mass is not zero, it hardly weighs more than the grin of a Cheshire cat. But taken together, the laboratory results confirm that neutrinos are perplexing particles. Are they different entities or a single species wearing different costumes? The implications of the recent measurements are far-reaching:

  1. Physicists believe that there are a billion neutrinos around for each nucleon (proton, neutron, etc.) so that if neutrinos possess just a hint of mass, they will dominate the mass of the universe; and

  2. Measurements of solar neutrinos fall short by a factor of three of what theory says the sun should spew out. This discrepancy could be explained if the solar neutrinos change from electron neutrinos to another form during their flight from the sun to earth, for the terrestrial neutrino detectors measure only electron neutrinos.

(Anonymous; "Do Neutrinos Oscillate from One Variety to Another?" Physics Today, 33:17, July 1980.)

From Science Frontiers #12, Fall 1980. 1980-2000 William R. Corliss