# Why is the beta emission in Wu's Experiment always in one direction but not the other?

I am learning the parity violation. In Wu's experiment, the electrons tend to emit always opposite to the direction of the electromagnetic field. My confusions are:

1.Why not the other way?

2.Does this have any relations with the fact that only left handed neutrinos interact with weak force?

3.What if we have found the right handed neutrinos and they also participate the weak interaction, will the electrons under this assumption emit both directions?

4.What I really want to know is how exactly does the left handedness affect the direction of the emission. If there is a term that affects the result, then I must be able to replace this term by adding a minus sign to turn it to a right handed result, in which I get an opposite result.

• the left handedness IS the direction of the emission. If you mean in the lagrangian of the interaction you should state it clearly Commented Nov 12, 2016 at 6:27

1.Why not the other way?

Physics is about experimental observations fitted with theoretical models. This was a basic observation that formed the mathematical models

2.Does this have any relations with the fact that only left handed neutrinos interact with weak force?

Yes , it forced the form of weak interaction that was incorporated in the model. The usefulness of theoretical models is that they are predictive, and the standard model with the weak interaction as decided is very successful in predicting new data, as at LHC.

3.What if we have found the right handed neutrinos and they also participate the weak interaction, will the electrons under this assumption emit both directions?

Theorists would have created the appropriate model to describe the behavior, but it would be for a different universe than the one we live in.

• Well, thanks for your answer. What I really want to know is how exactly does the left handedness affect the direction of the emission. And if there is a term that affects the result, then I must can replace this term by adding a minus sign to turn it to a right handed result . Commented Nov 12, 2016 at 6:16
• If you mean how the left handedness is included in the lagrangian of the standard model , you should be clearer in you question. As is you are asking :why left handedness, and the answer to that is "because that is what has been observed" Commented Nov 12, 2016 at 6:26