# Electrons and Positrons - Not elementary?

1. ### teflontactics

3
I was just thinking, as I do sometimes when my brain won't shut up and...

If an electron is an elementary particle, and a positron is an elementary particle, why do they share so many properties, and yet are different slightly in almost every way.

All the mass measurements show that the positron is lighter slightly, while still being the exact same "amount" of charge. It seems to me, that if E=mc^2, and the masses are different, with the speed of light being constant, then the energy level must be different.

If that was true, they wouldn't truly annihilate, as their charge would also be not equal.

So, If their charge energy is elementary, maybe there's a modifier particle that flips the charge, and therefore gives the electron more weight, and therefore a better "grasp" on the universe.

It could also explain why the universe has more matter than antimatter, as there's a weight difference in charge shifting (That modifier particle).

Just a brainstorm, thoughts?

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3. ### Dadface

2,069
Hello teflontactics.Are you sure they have slightly different masses?

4. ### fzero

2,601
Do you have a source for this conclusion about the relative masses? I think what you are failing to understand is that measurements of physical quantities like mass have an experimental uncertainty associated with them. When comparing two measurements, one must be careful to also take these uncertainties into account. What you will find is that the mass of the electron and the mass of the positron are equal, within the error range implied by the uncertainty.

The accepted value of the mass difference is $< 8\cdot 10^{-9}$ with a 90% confidence (http://pdglive.lbl.gov/popupblockdata.brl?nodein=S003DM&inscript=Y&exp=Y&fsizein=1). This is zero to within the accuracy with which we know the positron mass.

5. ### kurros

383
Well, wikipedia quotes the measured masses as being within just over 1 sigma of each other, so based on that there is no evidence of a discrepancy:
electron mass: 0.510998928(11) MeV/c^2
positron mass: 0.510998910(13) MeV/c^2

the PDG doesn't even list separate masses for the electron and positron, it just says electron mass=0.510998910(13). Also the wikipedia source for the electron mass is older than the one for the positron mass, so the slight discrepancy could just be due to one being slightly outdated.

I could believe there could in principle be some effect of CP violation which creates a tiny mass difference, although I have never heard about such a thing. What is your source that says the masses are different?

(edit): Yeah, what fzero said :p.

6. ### teflontactics

3
So you're saying all the textbooks I have, websites I've read, and written works which list the masses are just guestimates based on inaccurate data?

Okay, even so. Say an electron and positron are the same with inverse charges (which is worst case scenario if you can't even measure them accurately). What makes them even have inverse charges then?

They can't be the same and opposite concurrently. When the annihilate they produce gamma rays, so why can't the modifiers be mass less components of gamma particles?

That would make sense.

### Staff: Mentor

The Particle Data Group lists an upper limit for the electron-positron mass difference of ##8 \times 10^{-7}## percent; that is, no mass difference has actually been observed, and this is the limit of our current experimental techniques. If you have something that says differently, please post a reference.

(wow, I was "scooped" twice while I was writing and researching this)

I suggest that you click on the "Rules" link at the top of the page and note the section about Overly Speculative Posts. It's not part of our mission to help people develop their own theories here, such as your "modifier particle."

added:

All experimentally measured values, every last one of them, have uncertainties associated with them. Good experimenters estimate those uncertainties, and good sources tell you what those uncertainties are.

8. ### teflontactics

3
Okay, well sorry for wasting your time I guess.

Wasn't looking to postulate a theory, just looking to talk it out. I've got a unique outlook and nobody smart enough to talk it out with. I'll find a more accommodating audience, jtbell.

You can close this, moderators.

9. ### fzero

2,601
It's not that they're guestimates, its that it's impossible to do make a measurement without some inaccuracy due to your real-life measuring device. There are additional subtleties associated to complex experiments in particle physics, but a familiar example is that you can't measure length with a ruler more accurately than the finest lines drawn on the rulers edge.

The electron and positron are antiparticles of one another. Our current understanding of quantum mechanics is such that it is impossible to describe an electron without also including the positron in the description. There is no need to incorporate additional physics or particles to explain why we need to have the positron (with opposite electric charge).

10. ### Dadface

2,069
teflontonics,if you want more reliable and up to date information about data such as the constants it would be better to go to a site such as Kaye and Laby online,NPL or Nist.

Last edited: Mar 3, 2012
11. ### kurros

383
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