Cobalt 60 and parity violation

[goulio]

I'm considering the beta decay of a neutron into a proton an electron and an antineutrino. I heard that this was observed in 1957 in Cobalt 60. I don't really understand when the antineutrino comes into action...

The experimental results say that they detected more electrons in the direction opposite to the neutron spin. I understand that if parity was to be respected they should have got the same number of electrons in the direction of the neutron spin and in the opposite direction, but in what way is this related to the antineutrino? If you consider an illustration like the one on this page:

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/parity.html"

And you visualize the action of parity like a reflection by a plane perpendicular to the neutron's spin axis, the spin is reversed and the electrons linear momentum is reversed too, but what happens to the anti-neutrinos?

Any help greatly appreciated.

 

[mathman]

I don't fully understand your question, but as far as the antineutrino is concerned, it was originally proposed in the 1930's to conserve momentum, The proton and electron momenta didn't add up to that of the neutron. Also there is a question of spin. Neutrons, protons, and electrons all have half integer spins, To maintain balance another half integer spin particle was needed.

 

[sir-pinski]

Cobalt 60 is a radioactive isotope that undergoes beta decay, which is the process of a neutron turning into a proton, an electron, and an antineutrino. This was first observed in 1957 in the famous Wu experiment. The antineutrino is an important part of this process because it carries away some of the energy and momentum from the beta decay, helping to conserve energy and momentum in the overall reaction.

In terms of parity violation, it refers to the fact that the number of electrons emitted in the direction opposite to the neutron spin is greater than the number emitted in the same direction as the spin. This goes against the principle of parity, which states that the laws of physics should be the same when reflected in a mirror, or in this case, when the spin direction is reversed.

The role of the antineutrino in this is that it carries away some of the energy and momentum in the opposite direction to the electron, helping to balance out the total momentum in the reaction. Without the antineutrino, the number of electrons emitted in each direction would be equal and the principle of parity would hold.

To better understand this, you can think of the electron and antineutrino as a pair that are emitted in opposite directions, carrying away equal but opposite amounts of momentum. This helps to explain why the number of electrons is greater in the opposite direction to the neutron spin.

In summary, the antineutrino plays a crucial role in the beta decay of Cobalt 60, helping to conserve energy and momentum and contributing to the observed parity violation. I hope this helps to clarify any confusion you may have had about the role of the antineutrino in this process.