Lepton epoch

In physical cosmology, the lepton epoch was the period in the evolution of the early universe in which the leptons dominated the mass of the universe. It started roughly 1 second after the Big Bang, after the majority of hadrons and anti-hadrons annihilated each other at the end of the hadron epoch. During the lepton epoch the temperature of the universe was still high enough to create lepton/anti-lepton pairs, so leptons and anti-leptons were in thermal equilibrium. Approximately 10 seconds after the Big Bang the temperature of the universe had fallen to the point where lepton/anti-lepton pairs were no longer created.[1] Most leptons and anti-leptons were then eliminated in annihilation reactions, leaving a small residue of leptons. The mass of the universe was then dominated by photons as it entered the following photon epoch.

Astronomy: The Big Bang. The Lepton Era

References

^ The Timescale of Creation

Allday, Jonathan (2002). Quarks, Leptons and the Big Bang. Second Edition. ISBN 978-0750308069.

Timeline of the Big Bang
Augustinian era · Big Bang · Planck epoch · Grand unification epoch · Electroweak epoch (Inflationary epoch, Reheating, Baryogenesis) · Quark epoch · Hadron epoch · Lepton epoch · Photon epoch (Big Bang nucleosynthesis, Matter domination, Recombination) · Dark ages · Reionization