Why Aren't Atoms Made of Positrons and Antiprotons?

[zalnas]

I've recently learned more about antimatter, namely what types there are, and one question has stuck in my mind: why are atoms not composed of Positrons and Antiprotons? Since scientists at the LHC recently were able to contain antihydrogen, it seems that these atoms, while isolated from matter, are stable.

 

[Kevin_Axion]

Because of something called CP-Violation: http://en.wikipedia.org/wiki/CP_violation.

 

[mathman]

I've recently learned more about antimatter, namely what types there are, and one question has stuck in my mind: why are atoms not composed of Positrons and Antiprotons? Since scientists at the LHC recently were able to contain antihydrogen, it seems that these atoms, while isolated from matter, are stable.

Anti-matter in isolation is stable, as the LHC experiment demonstrated. However, when coming into contact with matter, there is mutual annihilation. As far as it is known, the universe is composed of baryonic matter (ordinary matter), dark matter, and dark energy. Anti-matter couldn't survive.

 

[zalnas]

Because of something called CP-Violation: http://en.wikipedia.org/wiki/CP_violation.

Perfect, thank you! That is exactly the explanation I was looking for.

Anti-matter in isolation is stable, as the LHC experiment demonstrated. However, when coming into contact with matter, there is mutual annihilation. As far as it is known, the universe is composed of baryonic matter (ordinary matter), dark matter, and dark energy. Anti-matter couldn't survive.

I was specifically wondering why antimatter didn't take precedence in the formation of the universe; I understand that it would not survive in the current state of the universe.

 

[fermi]

Because of something called CP-Violation: http://en.wikipedia.org/wiki/CP_violation.

In all known models (based on QFT) CP violation is necessary to produce baryon-antibaryon asymmetry. But it is far from sufficient, and definitely not automatic. The presence of CP violation does not automatically generate this asymmetry. Something far more subtle is needed in addition to CP violation. What that might be is model dependent, and it is a subject matter of much heated discussion. Needless to say, we do not know how exactly the baryon asymmetry arose in the early universe. There are plausible models, but that's all.

 

[Nik_2213]

If we were comprised of 'anti matter', and so considered it 'normal', would we know otherwise until the CP-violation surfaced ??