Superstring interactions

As a first step in the construction of a superstring field theory, the off-shelf vertex for coupling three arbitrary open superstring states is constructed. A cubic interaction term in the supersymmetry charge is also obtained. Since the Hamiltonian corresponds to the square of this supercharge, certain quartic interactions can be deduced as well. It appears likely, however, that the complete field theory of superstrings contains quartic and higher interactions in addition to those obtained here