  Form factors are derived for a model describing the coherent Josephson tunneling between two coupled Bose-Einstein condensates. This is achieved by studying the exact solution of the model in the framework of the algebraic Bethe ansatz. In this approach the form factors are expressed through determinant representations which are functions of the roots of the Bethe ansatz equations. 
Exact form factors for the Josephson tunneling current and relative   particle number fluctuations in a model of two coupled Bose-Einstein   condensates