What is a Neutrino?

Answer 1

It's really, really, small--less than 1/500,000th the mass of one electron. It's properties are not real well understood.

A group of Fermilab physicists in Illinois, apparently tiring of riding their bikes around the Tevatron, or feeding the geese in front of Wilson Hall, have been running an experiment wherein they have fired a few trillion muon neutrinos through the earth to the abandoned Soudan Iron Mine in Minnesota, 450 miles away, where they have constructed a 6,000-ton detector.

As of last spring, scientists estimated that if muon neutrinos were stable, the detector would have detected about 177 of them. Instead, they'd detected only 92 muon neutrinos. What happened to the other 85? They may have morphed into tau neutrinos or somehow decayed. The experiment continues!

Neutrinos might help explain the origin of protons, neutrons and electrons. They may account for some of the dark matter that gluts the universe, and also might help explain why the universe today consists almost entirely of matter and virtually no anti-matter.

Answer 2

Neutrinos are one of the fundamental particles which make up the universe. They are also one of the least understood.

Neutrinos are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons. Neutrinos are affected only by a "weak" sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it. If neutrinos have mass, they also interact gravitationally with other massive particles, but gravity is by far the weakest of the four known forces.

Three types of neutrinos are known; there is strong evidence that no additional neutrinos exist, unless their properties are unexpectedly very different from the known types. Each type or "flavor" of neutrino is related to a charged particle (which gives the corresponding neutrino its name). Hence, the "electron neutrino" is associated with the electron, and two other neutrinos are associated with heavier versions of the electron called the muon and the tau (elementary particles are frequently labelled with Greek letters, to confuse the layman). The table below lists the known types of neutrinos (and their electrically charged partners).

Answer 3

http://en.wikipedia.org/wiki/Neutrino

The neutrino is an elementary particle. It has half-integer spin () and is therefore a fermion. All neutrinos observed to date have left-handed chirality. Although they had been considered massless for many years, recent experiments (see Super-Kamiokande, Sudbury Neutrino Observatory, KamLAND and MINOS) have shown their mass to be non-zero. Because it is an electrically neutral lepton, the neutrino interacts neither by way of the strong nor the electromagnetic force, but only through the weak force and gravity.

Because the cross section in weak nuclear interactions is very small, neutrinos can pass through matter almost unhindered. For typical neutrinos produced in the sun (with energies of a few MeV), it would take approximately one light year (~1016m) of lead to block half of them. Detection of neutrinos is therefore challenging, requiring large detection volumes or high intensity artificial neutrino beams.

And on it goes.............................................

Answer 4

http://cupp.oulu.fi/neutrino/


Doug

Answer 5

It is something which is defined differently by many theorethical physisits. The most ununsual definition is by Dr Ricardo Carezani explained in the publication of the "Theory of Autodynamics."