Fermionic terms in the open superstring effective action

Abstract

We establish the α′ 2-terms in the abelian effective action for the massless modes of the open superstring ( A μ and ψ). Fermionic terms are found from the comparison with the known superstring four-particle scattering amplitudes. Independently, we compute them by supersymmetrization of the bosonic F 4-terms found previously. The standard supersymmetry transformations are modified by order α-terms.