Leptogenesis (physics)

The leptogenesis ( Fukugita - Yanagida scenario also ) is a theory for the dynamic creation of the baryon asymmetry in the early universe, which was proposed by the Japanese physicists M. Fukugita and T. Yanagida 1986.

It is a special model of baryogenesis, but is not a direct generation of the asymmetry between baryons and antibaryons from. Instead, the asymmetry is here initially between leptons and antileptons generated ( Leptonenasymmetrie ). Usually, results in an additional right-handed neutrinos, which have a very large mass and a singlet of the gauge group of the electroweak interaction form (normal neutrinos are left-handed and have a very small mass ). The decay of these additional neutrinos into leptons and Higgs bosons violates the CP symmetry, and therefore you get different numbers of leptons and antileptons. This asymmetry is then converted by sphaleron processes in the baryon asymmetry.

Extensions

There are now numerous extensions of the initial scenario.

Mid-1990s, for example, discovered by a research group at the University of Dortmund an opportunity to realize the scenario at energies that can be studied in the near future particle accelerators. In the usual scenarios, the leptogenesis at extremely high energies would have to be passed, so that an experimental verification of the model would be nearly impossible. The new scenario, usually referred to as the resonant leptogenesis, assumes that two of the heavy right-handed neutrinos have a mass almost identical, which leads to a resonant peak in the decay width.

Other popular extensions of the Fukugita - Yanagida scenario is the inclusion of supersymmetry (for example in the works of M. Plümacher ), the consideration of thermal effects in the early universe or effects that are associated with the fact that the Leptonasymmetrie not uniform over the three Fermiongenerationen distributed.

Due to the numerous extensions, the leptogenesis has become an extensive and sophisticated theory. Because of the many free and experimentally ( so far) not verifiable parameters, however, it is not possible to clearly say whether one of the many variants is capable of, the measured baryon asymmetry of the universe precisely predict. Therefore, the appeal of the theory is far more in their theoretical beauty, as it combines operations at very high energies, such as prevail shortly after the Big Bang, with physics at low energies, namely the physics of neutrinos. Thus, the same model can also be used for delivering a dynamic explanation of why the neutrinos have a very small, but still nonzero mass.