# Matter-antimatter question.

1. Aug 24, 2005

### mathman

One of the major open questions of particle physics is the existence of matter in the universe. At the time of the big bang, matter and antimatter were to supposed to have existed in equal quantities. What happened?

One thought I had (from out of nowhere) is that they do exist in equal amounts (numerically, not in mass), but we have been looking in the wrong place. My hypothesis is that electrons are antimatter. Moreover, the neutrinoes that are around are also antimatter. As a result there is a number balance. However, because of a yet to be discovered mechanism, the antiquarks or some predecessor antiparticles decayed into electrons and antineutrinoes, while the corresponding particles did not.

This just wild guessing - I have no evidence for it.

2. Aug 24, 2005

It is true that electron and neutrino both have antimatter particles, but why limit the existence of antimatter to these entities, why not also include anti-baryons and anti-mesons ? Both of these entities are known to be present in what we call "matter". If antimatter is in fact hidden within matter as a complex quantum superposition, then the problem is solved.

3. Aug 25, 2005

### mathman

You missed the point of what I was trying to say. Specifically, electrons are antimatter particles while positrons are matter particles. I was only concerned with stable particles. I know there is a whole zoo of mesons, etc. all of which have antipaarticles.

4. Sep 2, 2005

### samalkhaiat

This is what I call; TGT i.e total garbage theory, because we would be living in the anti-world and asking why is there so much anti-matter & not much matter.

5. Sep 2, 2005

### Astronuc

Staff Emeritus
By convention, which is always somewhat arbitrary, protons and electrons are considered matter - at least in our part of the universe.

Anti-protons (which have a negative charge = electron charge) and positrons (the positively charged counterpart of the electron) are considered antimatter.

When protons and anti-protons annihilate, they can form hyperon resonances or meson showers depending on the energy of initial anti-proton.

When positrons and electrons annihilate, they form two $\gamma$-rays with energies of at least 0.511 MeV each (the rest energy of an electron).

6. Sep 3, 2005

### mathman

One reason I am trying to see if electrons are better defined as antimatter is that the question of electrical neutrality of the universe can be answered as being a consequence of the fact that the matter-antimatter total must be in balance. By some unknown mechanism the antiprotons ended up as electrons.

7. Sep 3, 2005

### Astronuc

Staff Emeritus
A little problem with that scenario is that electrons are leptons and antiprotons are baryons.

The rest mass of an electron is 0.511 MeV, while the antiproton rest mass is 938.2723 MeV, and antiprotons are composed of three quarks (or anti-quarks $\bar{u}\bar{u}\bar{d}$)

Take a look at these frames at hyperphysics - something to mull over:

Astrophysics concepts and cosmology.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/astcon.html#c1

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/bbcloc.html#c6

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/bbang.html#c1

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/expand.html#c1

Particle concepts

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/parcon.html

Cosmology and Matter/anti-matter problem

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/cosmo.html#c3

Last edited: Sep 3, 2005
8. Sep 3, 2005

### cefarix

It is suspected by many physicists that the matter-antimatter discrepancy in the universe is due to the CP-symmetry violation of weak nuclear interactions. CP-symmetry violation occurs when a process which behaves a certain way under certain conditions does not behave the same way if the parity (up/down, right/left) is reversed and the charge is reversed (matter<-->antimatter). Clear evidence of this exists in the decay of what are called B-mesons. These particles consist of pairs of one quark and one antiquark. The particle can decay in many ways, but against the prediction of theory, it prefers to decay in some modes a bit more than others. It is this asymmetry that some believe caused a small amount of matter to be left over after the initial matter-antimatter annihilations of the early universe.

9. Sep 3, 2005

### Nereid

Staff Emeritus
It's a crazy, unreasonable, idea marcus, so it must be good!

As Astronuc has said, it's also very much agin the grain of the Standard Model of particle physics (leptons, hadrons, and all that). But who knows? Maybe some deep symmetry was broken very early on?

But wait! cefarix is onto something! If Sakharov was onto something, and CP violation is shown, experimentally (B factories, etc), to account for the observed matter-antimatter imbalance (as long as its embedded into a winning cosmological model, dontchya know), then we can all go the pub, right?

10. Sep 5, 2005

### mathman

I would like to clarify further the point that I was trying to make. There are (among others) two open cosmology questions in particle physics. First is the fact that the universe is made of matter. Second is the universe is electrically neutral.
In order to answer the first question, there needs to be some mechanism for antiquarks to disappear while leaving quarks behind. What I am trying to propose is that when this happens, electrons are part of the antiquark decay residue, thus taking care of the second question. That is why I am suggesting that electrons are antiparticles.
From what I have seen in SUSY theory, quark (and antiquark) decay into leptons is included, although to date no evidence of proton decay (demonstrating quark decay) has been seen.