Boundary spectrum in the sine-Gordon model with Dirichlet boundary conditions

We find the spectrum of boundary bound states for the sine-Gordon model wit h Dirichlet boundary conditions, closing the bootstrap and providing a comp lete description of all the poles in the boundary reflection factors. The b oundary Coleman-Thun mechanism plays an important role in the analysis. Two basic lemmas are introduced which should hold for any (1 + 1)dimensional b oundary field theory, allowing the general method to be applied to other mo dels.