Limits on sizes of fundamental particles and on gravitational mass of a scalar
We review the experimental limits on mass of excited fundamental particles and contact interaction energy scale parameters Λ for QCD, QED and electroweak reactions. In particular we have focused on the QED reaction measuring the differential cross-sections for the process e+e−→γγ(γ) at the energies from 91 GeV to 202 GeV using the data collected with the L3 detector from 1991 to 1999. With a global fit we set lower limits at 95% CL on Λ>1687 GeV, which restricts the characteristic QED size of the interaction region to Re<1.17×10−17 cm. All the interaction regions are found to be smaller than the Compton wavelength of the fundamental particles. This constraint is used to estimate a lower limit on the size of a fundamental particle related to gravitational interaction, applying the model of self-gravitating particle-like structure with the de Sitter vacuum core. It gives rτ⩾2.3×10−17 cm and re⩾1.5×10−18 cm, if leptons get masses at the electroweak scale, and rτ⩾3.3×10−27 cm,re⩾4.9×10−26 cm, as the most stri...