BPS STATES IN SUPERSTRINGS WITH SPONTANEOUSLY BROKEN SUSY (N=4-]N=2-]N=1)

We show the existence of a supersymmetry-breaking mechanism in string theory, where N = 4 supersymmetry is broken spontaneously to N = 2 and N = 1 with moduli-dependent gravitino masses., The BPS spectrum of th e theory with lower supersymmetry is in one-to-one correspondence with the spectrum of the heterotic N = 4 string. The mass splitting of the N = 4 spectrum depends on the moduli as well as the three R-symmetry charges. In the case of N = 4 --> N = 2, the perturbative N = 2 prepot ential is determined by the perturbative N = 4 BPS states. This observ ation led us to suggest a method that determines the exact non-perturb ative prepotential of the effective N = 2 supergravity using the shift ed spectrum of the non-perturbative BPS states of the underlying N = 4 theory.