Supersymmetric Wilson loops, superstring-like observables, and the natural coupling of superstrings to supersymmetric gauge theories

We obtain an explicit expression for the supersymmetric Wilson loop in terms of chiral superfields and supercurrents in superspace. In the abelian supersymmetric gauge theories, generalizing the super-particle coupling represented by the exponent of the supersymmetric Wilson loop, we show that there exists a unique dimensionless coupling of a superstring to abelian supersymmetric gauge theories that respects all known symmetries. The coupling is expressed in terms of chiral currents in superspace. This dimensionless superstring coupling gives rise to a new observable that is ''stringy'' in nature and has no analogue in non-supersymmetric gauge theories.