An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

An → elementary particle that does not participate in the → strong interaction. The Lepton family includes → electrons, → muons, tau leptons, → neutrinos and their → antiparticles. The lepton is a → fermion.

From Gk, lepto-, combining form of leptos "small, slight" + -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon; graviton), and other minimal entities or components.

Postulate that the magnitude of the lepton number density is comparable to or larger than the thermal radiation photon number density, so relaxation to equilibrium produces a degenerate sea of neutrinos. Degenerate neutrinos would suppress the number of neutrons relative to protons in the very early Universe; degenerate antineutrinos would suppress the number of protons relative to neutrons. Either case would affect BBNS (Peebles, P. et al., 2009, Finding the Big Bang, Cambridge: UK, Cambridge Univ. Press).

→ lepton; → degeneracy.

The era following the hadronic era, when the Universe consisted mainly of leptons and photons. It began when the temperature dropped below 10¹² degrees kelvin some 10^-4 seconds after the Big Bang, and it lasted until the temperature fell below 10¹⁰ degrees kelvin, at an era of about 1 second.

→ lepton; → era.

In particle physics, a quantum number attributed to elementary particles which is conserved in nuclear reactions. It is +1 for a lepton, -1 for an antilepton and 0 for other particles.

→ lepton; → number.

In → supersymmetry theories, a hypothetical → boson super-partner of a → lepton. See also → squark

s from → supersymmetry; → lepton.