Electron - positron annihilation

In summary, the conversation discusses the emission that occurs during electron-positron annihilation. The experts mention that the type of emission depends on the energy of the particles, with photons being created at lower energies and muon pairs being created at higher energies. They also note that various quantities, such as charge and lepton number, must be conserved during this process. Overall, the experts agree that only the total charge is conserved in annihilation events, rather than individual charges.
  • #1
ravisastry
52
0
Apologies if this question is already covered. I searched, but couldn't get info from pf. when electron-positron annihilation happens..what is emitted ? as per wiki, its gamma rays but on cern website i read that muon pairs(muon and anti muons) are emitted. which one is correct ?
 
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  • #2
It depends on the energy of the electron and positron. If they are low energy, the only things that can be created are photons; at higher energies there is some probability that muon-pairs will be produced, and at even higher energies even more massive particles can be produced.

As soon as the energy of the electron-positron pair exceeds the rest mass energy of a particle-anti-particle pair, I think there is some probability that it will be created.
 
  • #3
zhermes said:
It depends on the energy of the electron and positron. If they are low energy, the only things that can be created are photons; at higher energies there is some probability that muon-pairs will be produced, and at even higher energies even more massive particles can be produced.

As soon as the energy of the electron-positron pair exceeds the rest mass energy of a particle-anti-particle pair, I think there is some probability that it will be created.

If photons are created in annihilation, there won't be electric charge created in photons...but for Muon pairs, we have a positive and a negative muon. How can this be possible ?
 
  • #4
The total charge is conserved in both cases.
 
  • #5
ravisastry said:
If photons are created in annihilation, there won't be electric charge created in photons...but for Muon pairs, we have a positive and a negative muon. How can this be possible ?
There are numerous quantities you have to conserve; charge is one of them---which means that if a charged species is created (e.g. a muon, q = -e) another particle will also be created with the opposite charge (e.g. an antimuon, q = +e). Similarly, 'lepton number' needs to be conserved, energy, angular momentum (e.g. spin) etc etc.
 
  • #6
zhermes said:
There are numerous quantities you have to conserve; charge is one of them---which means that if a charged species is created (e.g. a muon, q = -e) another particle will also be created with the opposite charge (e.g. an antimuon, q = +e). Similarly, 'lepton number' needs to be conserved, energy, angular momentum (e.g. spin) etc etc.

dont we have charge conservation for that particular charges ? like instead of sum total...how about total no of negative (or positive) charges should remain the same pre & post the event ?
 
  • #7
ravisastry said:
dont we have charge conservation for that particular charges ? like instead of sum total...how about total no of negative (or positive) charges should remain the same pre & post the event ?
Nope. It's experimentally very well established that only the total charge is conserved.
Examples include:
pair production
electron capture
beta-radiation
black-holes
 

Related to Electron - positron annihilation

What is electron-positron annihilation?

Electron-positron annihilation occurs when an electron and a positron (the antimatter counterpart of an electron) collide and are converted into energy in the form of photons.

How does electron-positron annihilation happen?

When an electron and a positron collide, they undergo a process called annihilation where they are both destroyed and their mass is converted into energy in the form of gamma rays.

What is the significance of electron-positron annihilation in the field of physics?

Electron-positron annihilation is a fundamental process that helps us understand the nature of matter and antimatter. It also has practical applications in fields such as medical imaging and radiation therapy.

What is the energy released during electron-positron annihilation?

The energy released during electron-positron annihilation is equivalent to the total mass of the electron and positron multiplied by the speed of light squared, as described by Einstein's famous equation, E=mc².

Can electron-positron annihilation be reversed?

No, electron-positron annihilation is an irreversible process. Once the electron and positron are converted into energy, they cannot be reformed into their original particles.

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