Massive Type IIB Superstrings Part I: 3- and 4-Point Amplitudes

We present the 3- and 4-point tree-level scattering amplitudes involving first-massive states in closed Type IIB superstring theory, computed in the Minkowski vacuum. In particular, the 3-point amplitudes are computed for all possible combinations of first-massive and massless string states, and the 4-point amplitudes are computed for all such combinations involving at most two massive string states. We verify that unitarity is satisfied by checking the massless and first-massive poles of a 4-point amplitude. This paper is intended to serve as a reference providing all these amplitudes explicitly in consistent conventions as well as worldsheet correlators necessary to perform further computations beyond those listed here.