A test of the QED process e(+)e(-) --> gamma gamma>(*) over bar *(gamma) is
reported. The data analysed were collected with the DELPHI detector in 199
8 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the
centre-of-mass. The total integrated luminosity amounts to 375.7 pb(-1). T
he differential and total cross-sections for the process e(+)e(-) --> gamma
gamma were measured, and found to be in agreement with the QED prediction.
95% confidence level (C.L.) lower limits on the QED cut-off parameters of
Lambda (+) > 330 GeV and Lambda_ > 320 GeV were derived. A 95% C.L. lower b
ound on the mass of an excited electron of 311 GeV/c(2) (for lambda gamma =
1) was obtained, s-channel virtual graviton exchange was searched for, res
ulting in 95% C.L. lower limits on the string mass scale, M-S: M-S > 713 Ge
V/c(2) (lambda = 1) and M-S > 691 GeV/c(2) (lambda = -1). (C) 2000 Publishe
d by Elsevier Science B.V.