As I see from this discussion link there were no experiments where high energy electron beams were collided, only at low energy (VEP-1 collider in Novosibirsk, Russia). Assuming that standard model (SM) is correct we should see generation of electron-positron pairs in electron-electron-collisions when energies of the colliding electrons are high enough. So, the question is following. Should such experiments be done to test SM since if we will not see the electron-positron pairs the validity of SM is under a question.

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    $\begingroup$ At SLAC, 50GeV electrons go flying into a beam dump (with lots of electrons) all the time. And, how is this really different (in the SM context) from electron-positron scattering, which is also routinely done? $\endgroup$
    – Jon Custer
    Commented Feb 8, 2019 at 15:40
  • $\begingroup$ @Jon Custer The difference from electron-positron scattering is initial absence of positrons in the case of two electron beams. Then if we will see electron-positron pairs it will be clear answer. $\endgroup$
    – VYT
    Commented Feb 8, 2019 at 16:50
  • $\begingroup$ Related: physics.stackexchange.com/q/523557/123208 $\endgroup$
    – PM 2Ring
    Commented Dec 6, 2020 at 11:58
  • $\begingroup$ Note that 50 GeV electrons are moving with $\gamma\approx100000$. Of course you'll see pair production when they collide with other electrons. But you'll also get lots of bremsstrahlung. $\endgroup$
    – PM 2Ring
    Commented Dec 6, 2020 at 12:02
  • $\begingroup$ @PM 2Ring Ok, everybody will agree with your "of course" if we will see on practice pair production. Till this moment this is only a theoretical conclusion from SM. What I wanted to point out by this post that a such experiment is an important positive control for SM. For unknown reason this question is closed. And, a similar question (you referenced) posted one year later is open for discussion. What is this ? Subjective group thinking bias and now (when crisis in physics foundation is much more vocal in media than two years ago ?) people start to think that such experiment has sense ? $\endgroup$
    – VYT
    Commented Dec 7, 2020 at 16:06

1 Answer 1


Quite contrary to the answer mentioned in the link you provided, there were electron electron collision experiments. In fact, they were the first collider experiments that have been conducted.

So, electron electron collisions are also called Moller scattering which is well described quantitatively by the feynman rules for Quantum Electro Dynamics.

First, there is VEP-1 collider in Novosibirsk, Russia. It is a collider with an energy of $2*160 \,\mathrm{MeV}$. It reached a luminosity of $4*10^{28} \,\mathrm{cm^{-2}s^{-1}}$. The experimental studies on scattering of electrons were conducted and the following reactions were observed

$$e^{-} e^{-} \rightarrow e^{-} e^{-} \gamma$$

$$e^{-} e^{-} \rightarrow e^{-} e^{-} 2\gamma \tag{Double bremstrahlung}$$

So, the first reaction can be seen as a pair annihilation producing a photon. But, most probably it was from bremsstrahlung of either the initial or final states.

Secondly, there is also a collider in the US which is the Princeton-Stanford Experiment Collider. It was the most powerful electron accelerator during it's time. It is a collider with an energy of $2*500 \,\mathrm{MeV}$. It reached a luminosity of $2*10^{28} \,\mathrm{cm^{-2}s^{-1}}$. It has conducted several tests for QED.

QED is very well tested and understood. So, according to me we do not require a electron electron collider even at high energies today. I am more excited to see a Linear Collider of electron positron of higher energies or a muon anti-muon collider.

Also, if you would like to read about these colliders here is the link: https://arxiv.org/abs/1307.3116

  • $\begingroup$ I know about VEP-1 collider in Novosibirsk, Russia, this is why I have written "at high energy". From the VEP-1 collider results we can say that electron-positron pairs have not been detected, but it can be because low energy of electron beams. Do you know which results were in Princeton-Stanford Experiment Collider ? $\endgroup$
    – VYT
    Commented Feb 8, 2019 at 17:12
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    $\begingroup$ If you have access to the paper about Princeton-Stanford Experiment Collider results journals.aps.org/prl/abstract/10.1103/PhysRevLett.16.1127 can you look if the paper reports about electron-positron pairs detection ? $\endgroup$
    – VYT
    Commented Feb 8, 2019 at 17:32
  • $\begingroup$ I've taken the liberty of changing your markup to conform to the usual rule that units are typeset in upright text and set off by a thin space. And set your reactions as display equations while I was in there. $\endgroup$ Commented Feb 8, 2019 at 18:18
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    $\begingroup$ @VYT Thanks for sharing, I have access to the paper. So, in the paper they compared the observed angular distribution to the one expected from Moller scattering formula which includes feynman regularization and radiative corrections in it. They did not mention anything about observing electron-positron pairs. $\endgroup$
    – Invariance
    Commented Feb 8, 2019 at 20:07
  • $\begingroup$ @Invariance Thank you for the info! So, we can say nothing conforming about generation of electron-positron pairs from both the VEP1 and the Princeton-Stanford Experiment Collider. Should this control experiment be done, what do you think ? $\endgroup$
    – VYT
    Commented Feb 8, 2019 at 21:39

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