String theory predictions for future accelerators Original Research Article

We consider, in a string theory framework, physical processes of phenomenological interest in models with a low string scale. The amplitudes we study involve tree-level virtual gravitational exchange, divergent in a field-theoretical treatment, and massive gravitons emission, which are the main signatures of this class of models. First, we discuss the regularization of summations appearing in virtual gravitational (closed string) Kaluza–Klein exchanges in Type I strings. We argue that a convenient manifestly ultraviolet convergent low energy limit of Type I string theory is given by an effective field theory with an arbitrary cutoff Λ in the closed (gravitational) channel and a related cutoff Ms2/Λ in the open (Yang–Mills) channel. We find the leading string corrections to the field theory results. Second, we calculate exactly string tree-level three and four-point amplitudes with gauge bosons and one massive graviton and examine string deviations from the field-theory result.