In the 1983 journal article New Tests for Quark and Lepton Substructure which covers some science and mathematics behind quark and lepton composition (theoretical). It says:
Bhabha-scattering measurements imply that Λ > 750 GeV for the electron, a factor of 5 larger than previous bounds. I want to know what the article means when it refers to flavor-diagonal contact interactions and how it relates to the strong force.
I am confused how Bhabha scattering would imply the existence of preons. I am also confused how they derived the number 750 GeV; did they fire (protons? pions?) at a certain energy level and discover that the electron was still measured as pointlike, and then just conclude that the energy scale must thus be larger than 750 GeV because of that?
Here is the page in the article which I cited: