Parity violation in weak decays

In summary, there is a paradox in the extent to which parity is violated in weak decays. On one hand, Wu's experiment with electron emission shows a maximal violation of parity, while in nuclear β-decay, parity is mostly conserved. The extent of parity violation in nuclear β-decay varies, with some cases showing a violation as low as 0.1% or 1%. An example of someone using parity as a good symmetry in discussing beta decay is the case of La_{57} (J^P=2^-) → Ce_{58} (J^P=0^+) decay, where requiring l=1 results in the conservation of parity and angular momentum. However, there remains confusion as to why
  • #1
JoePhysicsNut
35
0
I am confused about when and to what extent parity is violated in weak decays.

On the one hand, there's Wu's famous experiment where electrons are emitted preferentially in one direction. This parity violation can be said to be maximal, since all electrons are emitted in one direction.

However, at the same time when determining the angular momentum and spin state of the electron-neutrino system in nuclear β-decay, I do use parity conservation as parity is mostly conserved.

Could anyone explain why parity is violated maximally in the case above and minimally in the other case? Also, to what extent (~0.1%, ~1%, etc of cases) is parity violated in nuclear β-decay?
 
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  • #2
Can you give us an example of someone using parity as a good symmetry when discussing beta decay?
 
  • #3
muppet said:
Can you give us an example of someone using parity as a good symmetry when discussing beta decay?

As an example, consider the
[itex]La_{57} (J^P=2^-)[/itex] → [itex]Ce_{58} (J^P=0^+)[/itex] decay and I'd like to figure out what the angular momentum and spin state of the electron-neutrino system is.

I get the right answer, when I require [itex]l=1[/itex] as this carries [itex]P=-1[/itex] making P conserved and [itex]S_{enu}=1[/itex] to conserve angular momentum overall.
 
  • #4
I think a fermion pair as the [itex](e,\nu)[/itex] pair has a negative intrisic parity, so with [itex]l=1[/itex] they should have a total of [itex]P=1[/itex]
 

1. What is parity violation in weak decays?

Parity violation in weak decays refers to the phenomenon where the weak force does not conserve parity, or mirror symmetry. This means that the laws of physics do not behave the same way when observed in a mirror reflection. This was first discovered in the 1950s through experiments on the decay of certain particles.

2. How does parity violation impact our understanding of the universe?

Parity violation in weak decays has greatly impacted our understanding of the universe by challenging the long-held belief that the laws of physics should behave the same way when observed in a mirror reflection. This discovery led to the development of new theories and principles in particle physics, and continues to contribute to our understanding of fundamental forces and the structure of matter.

3. What causes parity violation in weak decays?

The exact cause of parity violation in weak decays is still not fully understood. However, it is believed to be related to the asymmetry in the weak force's interaction with left-handed and right-handed particles. This is known as the chiral nature of the weak force, and it is not observed in the other fundamental forces.

4. Can parity violation be observed in everyday life?

No, parity violation in weak decays is not observable in everyday life. It is only noticeable in the microscopic world of particle physics, and it requires specialized equipment and experiments to detect and measure it.

5. How is parity violation in weak decays measured?

Parity violation in weak decays is measured through experiments that observe the decay products of certain particles. By examining the angular distribution of these decay products, scientists can determine if parity is violated in the decay process. This has been confirmed through numerous experiments and is now a well-established phenomenon in particle physics.

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