If quarks and leptons are composite at the energy scale Λ, the strong forces binding their constituents induce flavor-diagonal contact interactions, which have significant effects at reaction energies well below Λ. Consideration of their effect on Bhabha scattering produces a new, stronger bound on the scale of electron compositeness: Λ>750 GeV. Collider experiments now being planned will be sensitive to Λ~1-5 TeV for both electrons and light quarks.
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Eichten et al. (1983) studied this question.
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