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lpetrich
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Particle Data Group - 2017 Review has some strong lower limits for the mass scales of possible quark and lepton compositeness, or at least the compositeness of the easier-to-study ones, like up and down quarks and also electrons. The limits are well into the TeV range, though they are somewhat model-dependent.
This means that electrons, up quarks, and down quarks do not start to disintegrate even after applying energies a million times their rest masses.
Here are the maximum ratios of disintegration energy to rest mass for entities previously discovered to have been composite:
But there is a theoretical analogy: light mesons, like pions. Their mass is roughly sqrt(mq*mc) where mq is the quarks' average mass and mc = QCD energy scale. For mq << mc, m(meson) << mc also. So if the electron has a compositeness scale of about 1 TeV, then the electron's constituents would have to have masses around 1 eV.
This means that electrons, up quarks, and down quarks do not start to disintegrate even after applying energies a million times their rest masses.
Here are the maximum ratios of disintegration energy to rest mass for entities previously discovered to have been composite:
- Atoms: 10^(-8) (ionization of hydrogen atoms)
- Nuclei: 10^(-3) (dissociation of deuterons)
- Hadrons: 1 (deep inelastic scattering off of nucleons)
But there is a theoretical analogy: light mesons, like pions. Their mass is roughly sqrt(mq*mc) where mq is the quarks' average mass and mc = QCD energy scale. For mq << mc, m(meson) << mc also. So if the electron has a compositeness scale of about 1 TeV, then the electron's constituents would have to have masses around 1 eV.