When is weak interaction a force?

In summary, weak interaction can be considered a force rather than just a cause of some processes when it is involved in elastic scatterings that change only momentum but not taste. However, it still operates as a process and is over as the particles depart. The weak force has different symmetries and selection rules compared to the electromagnetic force, and operates only on left helicity particles. While there are no known systems bound by weak force, its effects can be observed by studying perturbations in other bound systems. These perturbations include an extremely small impact on energy levels and a lack of perfect parity invariance in atoms.
  • #1
snorkack
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When is weak interaction actually a force, rather than merely cause of some process?
Not in beta decay - it is process.

There are simpler weak interaction processes around: elastic scatterings that change only momentum but not taste. But those are still processes and are over as the particles depart.
Electrons are stuck in atoms for a long time. They undergo electron capture - but the eventual capture is still a process, and over as the neutrino departs.

But an electron should also undergo elastic scattering from nucleus by weak force.
The electron also undergoes elastic scattering from nucleus by the far stronger electromagnetic force.
But weak force has different symmetries and selection rules! Not only does weak force operate differently on left and right helicity particles - which electromagnetic force cannot - but weak force operates only on left helicity particles.

So consider a s electron in an atom. The type of orbitals that for part of orbit enter the nucleus into weak force range
No orbital angular momentum, so no spin-orbit interaction.

Suppose the nucleus also has no spin - neutrons and protons paired - so no interaction of electron spin with nuclear spin.
How will the weak force distort the orbitals? What kind of asymmetry does it introduce into the orbital that does not follow from the electromanetic potetial?
 
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  • #2
snorkack said:
There are simpler weak interaction processes around: elastic scatterings that change only momentum but not taste. But those are still processes and are over as the particles depart.
How is that fundamentally different to elastic electron/electron scattering for example?

I think you are just unnecessarily trying to make your own definitions of words.
 
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  • #3
mfb said:
How is that fundamentally different to elastic electron/electron scattering for example?

I think you are just unnecessarily trying to make your own definitions of words.
In case of elastic electromagnetic scattering, you cannot easily detect whether the force was repulsive or attractive. Because the true location of electron suffers Heisenberg uncertainty, if you see an electron deflected to the right, you cannot tell apart an electron that passed to the right of an electron and was repelled from an electron that passed to the left of a positron and was attracted.
In case of electrostatic interaction, it is strong enough to bind bound systems. Confirming the force is attractive.

But there are no known systems bound by weak force.
So, how can the effects of weak force be resolved?
Observe systems bound by other forces, and examine them for perturbations caused by weak force.

So what are the perturbations of atoms caused by weak interaction between electron and nucleus?
 
  • #4
snorkack said:
Because the true location of electron suffers Heisenberg uncertainty, if you see an electron deflected to the right, you cannot tell apart an electron that passed to the right of an electron and was repelled from an electron that passed to the left of a positron and was attracted.
You can, by looking for the electron or positron recoil.
snorkack said:
But there are no known systems bound by weak force.
So what?
snorkack said:
So what are the perturbations of atoms caused by weak interaction between electron and nucleus?
There is an extremely small impact on the energy levels from Z exchange. I'm not sure if that has been measured. It also means atoms are not perfectly parity invariant. Here is a discussion.
 
  • #5
Hi,

snorkack said:
So what are the perturbations of atoms caused by weak interaction between electron and nucleus?

The range of the weak interaction is shorter than the size of an atom (although s-orbitals overlap the nucleus...)

Regards,
ORF
 

1. What is weak interaction?

Weak interaction is one of the four fundamental forces of nature, along with gravity, electromagnetism, and strong interaction. It is responsible for the decay of subatomic particles and plays a crucial role in nuclear reactions.

2. When does weak interaction occur?

Weak interaction occurs when subatomic particles interact with each other through the exchange of W and Z bosons. It is the weakest of the four fundamental forces and only has a significant effect at extremely short distances.

3. How does weak interaction differ from other forces?

Unlike gravity and electromagnetism, which have infinite range, weak interaction has a very short range and only affects particles within the nucleus of an atom. Additionally, unlike the other forces, weak interaction does not conserve energy, charge, or parity.

4. When is weak interaction considered a force?

Weak interaction is considered a force when it causes a change in the properties of a particle, such as its mass or charge. This can occur during radioactive decay or in nuclear reactions.

5. How does weak interaction contribute to our understanding of the universe?

Weak interaction plays a crucial role in the formation of elements in the universe. Without it, stars would not be able to produce the heavier elements necessary for life. Additionally, studying weak interaction helps us understand the fundamental building blocks of matter and the forces that govern their interactions.

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