# what happens to positrons after pair production

what happens to positrons after pair production?

There are two possible outcomes, but which one is true or most probable?

1. The particle antiparticle pair have enough kinetic energy to overcome the electrostatic attraction between so they will move away indefinitely in opposite directions
2. They do not have enough energy so they will undergo annihilation such that either a) The pair eventually annihilate, but can be observed before they do so (i.e. they are real or "on-shell"), and b) The pair annihilate essentially immediately after creation, and are not observed separately but rather modify the behavior of another process (i.e. they are virtual or "off-shell"),
• You might want to divide the second possibility into two parts, because different physics are involved in each: 2a. The electron and positron eventually annihilate, but can be observed before they do so (i.e. they are real or "on-shell"), and 2b. The electron and positron annihilate essentially immediately after creation, and are not observed separately but rather modify the behavior of another process (i.e. they are virtual or "off-shell"). Oct 12, 2018 at 19:04
• So annihilation stakes place regardless Oct 12, 2018 at 19:14
• Annihilation with some electron is virtually guaranteed, eventually. The indistinguishability of electrons makes the distinction between which electron the positron meets a dodgy proposition, at best. Oct 12, 2018 at 19:23
• The gist here that in the presence of other electrons it is unlikely that the same positron and electron annihilate each other. The positron can be annihilated by any electron.
– MaxW
Oct 12, 2018 at 19:24
• So the answer to my question would simply be annihilation takes place Oct 12, 2018 at 19:34

$$hv = 2m0c^2 +E^++E^-$$
$$hv > 2m0c^2$$