Illustration of three scenarios for deuteron production and interaction with pions (left) and the resulting \piPMd correlation functions (right). All scenarios include Coulomb attraction between $\pi^-$--d (green curves) and Coulomb repulsion between the $\pi^+$--d (red curves). The dashed lines always show the correlation function using Coulomb interaction. Scenarios (i) and (ii) represent thermally-produced deuterons with only Coulomb and Coulomb+elastic+inelastic interactions, respectively. Scenario (iii) depicts deuteron formation via nuclear fusion following $\Delta$-resonance decays. All the simulations include the charge conjugates ($\piPd \equiv \piPd\oplus \piMdbar$ and $\piMd \equiv \piMd\oplus\piPdbar$). The bands width corresponds to the statistical uncertainties of the models.