  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.
