Matter vs Antimatter: What Happens When They Collide?

[42Physics]

Quick, probably obvious, question. If there was equal amounts of matter and antimatter and they collided and exploded, what happened after the 'battle played out ;)' ? Why is there more matter then antimatter...? Shouldn't there be the same amount?

 

[mfb]

CP violation lead to a small difference between antimatter and matter, so some matter remained.
The observed CP violation is not sufficient to explain the remaining matter today, this is one of the unsolved puzzles of particle physics / cosmology.

 

[retro10x]

Another quick (maybe not?) question to add onto the original question: why do we assume that if there were equal amounts, all of the anti-matter would have collided with matter (account for CP violation if you want, same question holds)? Why is it unreasonable to propose that there is a large amount of anti-matter elsewhere in the universe and where there is very little "normal" matter? Obviously we haven't seen any evidence of this, but what have we seen that refutes this?

Forgive my naivety

 

[mfb]

If antimatter would be dominant somewhere else, there would be a border between matter- and antimatter-regions. Annihilation would lead to significant radiation. In addition, I doubt the cosmic microwave background would look the same - it was emitted long after those processes, in a time where interactions between particles were still very common.