Quasi-real Compton scattering measurement☆

Abstract A measurement is reported on the elastic scattering of quasi-real photons generated by one beam with the particles of the other in e + e − interactions at s = 29 GeV performed using the DELCO detector at PEP. The events are characterized by coplanar and anti-tagged e γ pairs with large visible energy where the charge of the electron is correlated with the acolinearity angle. Also, this result is used to search for the on-shell production of a hypothetical excited electron e ∗ . It is found that the data agree well with the predictions for the QED Compton process, and upper limits are set on the e ∗ e γ coupling parameter λ to be below 10 −2 (95% CL) in the range 15 ≲ M e ∗ ≲ 27 GeV .