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Because mass hierarchy of charged leptons is strong, approximation of [O.sub.l] is
Elementary particles can be categorized into hadrons and leptons in accord with whether they participate in the strong interaction or not.
where E, [E.sub.v] are the total energies of emitted leptons, and A and B are the usual decay asymmetry parameters arising from parity violation for the charged lepton and the neutrino, respectively.
The fundamental particles of matter are in two families, leptons and quarks.
Up to this point, the leptons that were known included the electron, the electron neutrino, and their antiparticles and the muon, the muon neutrino, and their antiparticles.
That year, Perl was finding hints in the debris of collisions between high-energy electrons and positrons of a hitherto undiscovered lepton. Although some theorists had suggested that heavy leptons exist, no one was certain that any would be found (SN: 9/12/92, p.174).
While there may be only twelve leptons (see above), there are a large number of hadrons, beginning with the pion, which is the least massive hadron, through over a hundred more massive ones.
interacting fundamental particles, or quarks, and six weakly interacting particles, or leptons. The particles in each sextet come in pairs, and these pairs can be neatly arranged in order of increasing mass.
Last week, five separate teams of researchers reported evidence that, taken together, limits to three the number of families of fundamental particles known as quarks and leptons that can exist.
Underneath the standard model is the realm of "compositeness.' The standard model holds that everything is built out of six kinds of quarks and six kinds of leptons, and that these quarks and leptons are the most elementary forms of matter.
The most widely believed theory at thispoint holds that the elementary building blocks of matter consist of six quarks and six leptons. Neutrinos and muons are leptons and so are believed to be simple elementary particles.