# Big bang related question

1. Jul 4, 2011

### Deepak247

Ive heard that soon after the big bang matter and antimatter was created in equal proportions and that majority of the matter-antimatter annihilated among each other, somehow only a small fraction of matter remained......... my question is....

what was the form of the matter or antimatter which was annihilated?

was it mostly in baryons or mesons? i.e. mostly baryons annihilating among each other or mesons annihilating among each other?

what was the ratio?

2. Jul 4, 2011

### bapowell

positrons with electrons; quarks with antiquarks

3. Jul 4, 2011

### Deepak247

ok but how much was proton-antiproton and neutron-antineutron annihilation there?

i mean to say baryon annihilation...was it significant?

4. Jul 4, 2011

### bapowell

As I said, there was annihilation between quarks and antiquarks -- not baryons. The initial asymmetry between quarks, $q$, and antiquarks, $\bar{q}$ was in fact not significant:
$$\frac{n_q - n_{\bar{q}}}{n_q} \simeq 10^{-8}$$

5. Jul 5, 2011

### Deepak247

but if we look at the big bang timeline especially the hadron and lepton epoch...
http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang

it hints that protons, neutrons and their respective antiparticles were annihilated among each other....werent they?

6. Jul 5, 2011

### bapowell

Yes, that is correct. Sorry, I was mistaken. The initial asymmetry was setup during baryogenesis, prior to baryon formation; the annihilations occurred between baryons after the QCD phase transition.