Why is the Decay of Neutral Pion to Electron Positron Pair Forbidden?

In summary, the decay of neutral pion to electron positon pair is not forbidden, although it is slower than the two photon decay due to the need for two virtual photons. It is considered "forbidden" in terms of its second order rate, but this depends on the definition of "forbidden". Additionally, it violates helicity conservation, which is expected for the leading order in the Bjorken limit. It is also helicity suppressed.
  • #1
ruchika
3
0
Why the decay of neutral pion to electron positon pair is forbidden?
 
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  • #3
you know, way back when i wrote down on a test that this decay was forbidden. my professor has a good laugh: he told me that i just "disproved" his PhD thesis!
 
  • #4
it is not forbidden, I did my Diploma thesis on that decay! ;-P

i.e I am in the same situation as blechman's teacher was ;-)
 
  • #5
The decay into electron-positron has to proceed through two virtual photons, one leading to the e-p pair and the other being absorbed by one of the pair. This makes the pi-->e p
rate much slower than the two gamma decay.
If the term "forbidden" is used in the way it is used in beta decay, then the e-p is
"forbidden", as confirmed by the experimental rate.
 
  • #6
it is second order, so it depends on what one means by "forbidden"
 
  • #7
malawi_glenn said:
it is second order, so it depends on what one means by "forbidden"
Here I think it means that it violates helicity conservation (which is expected for the leading order in the Bjorken limit).
 
  • #8
malawi_glenn said:
it is second order, so it depends on what one means by "forbidden"

Isn't it also helicity suppressed?
 
  • #9
LongLiveYorke said:
Isn't it also helicity suppressed?


yes, see the post above yours =)
 

1. Why is the decay of neutral pion to electron positron pair forbidden?

The decay of the neutral pion to an electron-positron pair is forbidden due to conservation of energy and momentum. The pion, being a spin-zero particle, cannot decay into two spin-half particles such as the electron and positron, as this would violate the laws of conservation of angular momentum.

2. What is the significance of the decay of neutral pion to electron positron pair?

The decay of the neutral pion to an electron-positron pair is significant because it is a rare process that can provide insights into the fundamental forces and interactions at play in the universe. It is also important for understanding the properties of the pion, which is a key particle in the study of nuclear matter and the strong nuclear force.

3. How is the decay of neutral pion to electron positron pair related to the weak nuclear force?

The decay of the neutral pion to an electron-positron pair is mediated by the weak nuclear force. This force is responsible for certain types of radioactive decay and is one of the four fundamental forces in nature. The decay of the pion to an electron-positron pair is a manifestation of the weak nuclear force acting on the particles involved.

4. Is the decay of neutral pion to electron positron pair ever observed?

Yes, the decay of the neutral pion to an electron-positron pair has been observed in high-energy particle collisions. However, it is a very rare process and is only seen in certain conditions. The decay has also been studied and observed in laboratory experiments using particle accelerators.

5. How does the decay of neutral pion to electron positron pair affect particle physics theories?

The decay of the neutral pion to an electron-positron pair is one of the processes that has been used to test and validate theories in particle physics, such as the Standard Model. The observation of this decay and its properties can provide insights into the fundamental forces and particles that make up our universe and help refine our understanding of these theories.

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