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The name lepton comes from the Greek λεπτฯς leptós, "fine, small, thin" (neuter nominative/accusative singular form: λεπτฯν leptón); [14] [15] the earliest attested form of the word is the Mycenaean Greek ๐ฉ๐ก๐ต, re-po-to, written in Linear B syllabic script. [16] Lepton was first used by physicist Léon Rosenfeld in 1948: [17]
A hadron is a composite subatomic particle.Every hadron must fall into one of the two fundamental classes of particle, bosons and fermions. In particle physics, a hadron (/ ห h æ d r ษ n / โ; from Ancient Greek แผδρฯς (hadrós) 'stout, thick') is a composite subatomic particle made of two or more quarks held together by the strong interaction.
In cosmological models of the Big Bang, 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. [1]
Leptons, on the other hand, are not composed of quarks and as such do not participate in the strong interaction. The best known baryons are protons and neutrons , which make up most of the mass of the visible matter in the universe , whereas electrons , the other major component of atoms , are leptons.
Quarks are the fundamental constituents of hadrons and interact via the strong force. Quarks are the only known carriers of fractional charge , but because they combine in groups of three quarks (baryons) or in pairs of one quark and one antiquark (mesons), only integer charge is observed in nature.
In physical cosmology, the hadron era [1]: 209 is said to have begun at a time of 10-44 seconds, or at 10-8 seconds [2], and ended at 10-4 seconds. The temperature was high enough to allow the formation of hadron/anti-hadron pairs, which kept matter and anti-matter in thermal equilibrium.
The hadrons are divided by number of quarks (including antiquarks) into the baryons containing an odd number of quarks (almost always 3), of which the proton and neutron (the two nucleons) are by far the best known; and the mesons containing an even number of quarks (almost always 2, one quark and one antiquark), of which the pions and kaons ...
LEP was a circular lepton collider – the most powerful such ever built. For context, modern colliders can be generally categorized based on their shape (circular or linear) and on what types of particles they accelerate and collide (leptons or hadrons). Leptons are point particles and are relatively light. Because they are point particles ...