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

Click For Summary

Discussion Overview

The discussion centers around the decay of the neutral pion (π0) into an electron-positron pair, exploring whether this decay is forbidden and the implications of its rarity. The scope includes theoretical considerations, experimental observations, and the nuances of particle decay processes.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether the decay of the neutral pion to an electron-positron pair is truly forbidden, with references to personal experiences in academic settings.
  • One participant mentions that the decay can occur through two virtual photons, leading to a slower rate compared to the two gamma decay.
  • Another participant highlights that the term "forbidden" may depend on the context, particularly in relation to helicity conservation and the decay's order.
  • There is a suggestion that the decay is second order and may be helicity suppressed, indicating a complex relationship between theoretical predictions and experimental results.

Areas of Agreement / Disagreement

Participants express differing views on whether the decay is forbidden, with some arguing it is not forbidden while others suggest it is context-dependent. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants note that the decay's classification as "forbidden" may vary based on definitions and theoretical frameworks, particularly regarding helicity conservation and decay rates.

ruchika
Messages
3
Reaction score
0
Why the decay of neutral pion to electron positon pair is forbidden?
 
Last edited:
Physics news on Phys.org
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!
 
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 ;-)
 
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.
 
it is second order, so it depends on what one means by "forbidden"
 
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).
 
malawi_glenn said:
it is second order, so it depends on what one means by "forbidden"

Isn't it also helicity suppressed?
 
LongLiveYorke said:
Isn't it also helicity suppressed?


yes, see the post above yours =)
 

Similar threads

Undergrad How often would a ϕ meson decay to a electron-positron pair?
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Tau Decay: More Pions, Less Ratio?
  • · Replies 5 ·
Replies
5
Views
2K
High School Beta Plus Decay: What's Left for the Electron?
  • · Replies 8 ·
Replies
8
Views
3K
Undergrad What is the meaning of 'CP violation' in the Cronin and Fitch experiment?
  • · Replies 10 ·
Replies
10
Views
2K
Graduate Experimental Signatures of Neutral Pion Decay at High Energies
  • · Replies 10 ·
Replies
10
Views
4K
Undergrad Why does the long-lived kaon only rarely decay to two pions?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Forbidden decay ##\rho^0\rightarrow \pi^0\pi^0##
  • · Replies 4 ·
Replies
4
Views
4K
Graduate Why KE of Annihilation Electrons Differs?
  • · Replies 11 ·
Replies
11
Views
2K
Undergrad Positron decay direction from muon
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad Why is a pair of an electron and a positron unstable?
  • · Replies 14 ·
Replies
14
Views
4K