What isa Neutrino??????

Is it another word for a photon?? I know it is extremely small sometimes called massless, but is it larger than a lepton or quark?

The neutrino…or “little neutral one” was discovered by Enrico Fermi as a way to explain the extra energy left over from a nuclear reaction. These particles have no charge and is almost completely transparent to matter (a neutrino can pass throught lightyears of lead). Only rarely does a neutrino react measurably when it collides with an atomic nucleus. The various neutrino detectors in the world are great tanks filled with cleaning fluid, surrounded by photoreceptors, buried deep underground (to minimize solar and man-made radioactive emissions).
One of the great mysteries of science is wether or not a neutrino has mass or not (if they do, then they could be part of the missing mass of the universe, explaining the possibility of the universes ultimate fate…keep on expanding forever, or collapse in the Big Crunch).

Its what they are replacing all the defective old trino’s with.

In addition to balancing out the tiny little amount of undetected mass-energy in a nuclear reaction, neutrinos also account for the conservation of “Lepton number” in a particle decay.

“Lepton number”, abbreviated L, is one of those quantities that’s supposed to be conserved in every reaction. All leptons have L=1, all anti-leptons have L= -1, and all other particles have L=0. When a neutron (n) decays, it is observed to turn into a proton § and emit an electron (e[SUP]-[/SUP]), like so:

n --> p + e[SUP]-[/SUP]

Now, a neutron is L=0, a proton is L=0, and an electron is L=1, so the observed reaction has a total L of 0 on the left-hand side of the --> sign and a total L of 1 on the right. This violates the conservation of L. There must be another, undetected particle involved – either something with L=1 on the left-hand side or something with L= -1 on the right-hand side. The prediction was that the production of an electron, since it was a decay involving the Weak Force, would also produce an anti-electron neutrino, like so:

n --> p + e[SUP]-[/SUP] + (anti-electron neutrino)

An anti-electron neutrino has L= -1, which brings the total L on the right-hand side of the equation to 0. Thus this reaction does conserve L.