CIEMAT Publications

Abstract

We classify the possible deviations from the Standard Model in the QED-dominated e+e- → γγ, process under the assumption of a preserved SU (2)L × U (1)Y symmetry. We nd that the only deviations really observable in practice correspond to a correction of the dierential cross section by a factor (1+C8s2/(2απΛ4)sin2 θ), where Λ is the scale of new physics, θ is the polar angle of any of the nal state photons and c8 is a constant of order 1. We also provide sensitivity estimates for QED deviations at future e+e- facilities. An e+e- collider operating at s1/2= 3 TeV could provide sensitivity to Λ scales as large as 15 TeV, provided that acceptances and eciencies are controlled at the per mille level. Finally, we also discuss the possibility of a measurement of the luminosity at the FCC-ee con precisiones ≲ 10-4, FCC-ee with ≲ 10-4 precision, using analyses of the e+e- → γγ process at s1/2≈ mZ.