Baryon asymmetry

The baryon asymmetry of particle physics is the observed great dominance of matter over antimatter in the universe. It is one of the most important not yet understood phenomena in particle physics, as it cannot be explained by the Standard Model .

The baryon asymmetry is determined by

${\displaystyle \eta ={\frac {n_{B}-n_{\bar {B}}}{n_{\gamma }}}>0}$

${\displaystyle \Rightarrow n_{B}\gg n_{\bar {B}}}$

With

• the number of baryons as a measure of the amount of matter ${\displaystyle n_{B}}$
• the number of antibaryons (the antiparticles of the baryons) as a measure of the amount of antimatter ${\displaystyle n_{\bar {B}}}$
• the number of photons . ${\displaystyle n_{\gamma }}$

The observed numerical value

${\displaystyle \eta =(6{,}14\pm 0{,}25)\cdot 10^{-10}}$

could so far be determined most precisely from the data of the WMAP satellite from the cosmic background radiation .

Baryon asymmetry in the universe

The amount of antimatter in the universe cannot be determined directly because astronomers cannot distinguish it from matter. With the annihilation of matter and antimatter, however, a characteristic electromagnetic radiation occurs, which, however, could never be observed. This means that if there were large amounts of antimatter in space, it would have to be separated on large scales from the areas in which matter dominates - such as on Earth, in the solar system and the Milky Way. However, this can largely be ruled out by the cosmological models.

Theories of Generation

In the past it was generally assumed that the baryon asymmetry is an initial condition for our universe that was fixed at the time of the Big Bang . Since the baryon asymmetry would have been greatly reduced in the course of inflation , the initial asymmetry would also have to have been inexplicably large.

Today, the speculative theories of baryogenesis and leptogenesis , which so far could not be verified experimentally, predict a dynamic generation of asymmetry during the Big Bang.

See also

• CP violation
• LHCb
• Supersymmetry

literature

Laurent Canetti, Marco Drewes, Mikhail Shaposhnikov: Matter and Antimatter in the Universe . In: New J.Phys. . 14, 2012, p. 095012. arxiv : 1204.4186 . bibcode : 2012NJPh ... 14i5012C . doi : 10.1088 / 1367-2630 / 14/9/095012 .

Individual evidence

1. ↑ Richard H. Cyburt, Brian D. Fields, Keith A. Olive: Primordial Nucleosynthesis in Light of WMAP . In: Phys.Lett.B . 567, 2003, pp. 227-234. arxiv : astro-ph / 0302431v2 . doi : 10.1016 / j.physletb.2003.06.026 .