In the mid-1950s, particle physicists had acquired some experience with three recently discovered unstable particles called pi-mesons or pions and their weak interaction decay characteristics. In 1957 Lederman observed the following decay processes:
where the plus and minus pions decay into muons , antimuons, muon antineutrinos and muon neutrinos.
Because neutrinos are uncharged and do not feel the strong force, they are practically ghost particles they rarely interact with anything and hence are extremely difficult to detect. However, muons are charged and can easily be observed in the laboratory.
For decay processes in which the pions are initially at rest, the daughter particles must come out back to back in order to conserve momentum. By following the spins and directions of the outgoing muons, Lederman was able to deduce the following rule:
Due to neutrinos must be massless and travel at the speed of light if these laws are to hold. Otherwise, a Lorentz transformation could be used to effectively make a neutrino travel in a direction opposite to its line of motion, and the above rules would not hold; in that case, neutrinos and their antimatter partners would both exhibit left and right handedness.
Due to Standard model has neutrino massless.
But is neutrino massless? Oscillation of solar neutrinos shows that not, they are not massless.
We are able detect a neutrino only indirect way, through weak decay, where is a product of decay with another well described usually charged particles, which we can well detect. Than as we know R-handed particles are not interacting via weak decay, non diagonal elements of SU(2) matrix.
That mean, what we can say is, R-neutrinos not interacting in weak interactions, than ALL NEUTRINOS IN WEAK DECAY ARE LEFT-HANDED. This sentence not exclude a existence of R-HANDED NEUTRINO.
http://cosmoso.net/chirality-and-the-asymmetrical-universe/
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