Bosonization and BRST invariant three-superstring Caneschi-Schwimmer-Veneziano vertex

Requiring the equivalence to the non-bosonized BRST invariant Caneschi-Schwimmer-Veneziano vertex (CSV vertex) for the Neveu-Schwarz sector of the superstring, we first construct the bosonized representation of the three-string CSV vertex for all fermionic fields and bosonic ghosts in the superstring. Taking the product of all these vertices and requiring the constraint equations for the bosonized operators as well as for the spin operator, we construct the bosonic representation of the three-superstring CSV vertex. Imposing of the GSO projection, the resulting vertex is applicable to the coupling of any type of three-string states with arbitrary Bose sea level, including also the Ramond sector. The geometrical meaning of the constraint equation and the characterization of the CSV vertex as a transition operator are discussed. (orig.)