Polarized hadron pair production from electron-positron annihilation

We study the production of two almost back-to-back hadrons from the annihilation of an electron and a positron, allowing for the polarization of all particles involved. In particular, we conduct a general (model-independent) structure function decomposition of the cross section for the case $e^+e^- \to \gamma^* \to h_ah_bX$. Moreover, using the parton model we calculate the relevant structure functions in terms of twist-2 transverse momentum dependent (TMD) fragmentation functions (FFs). We also give results for the situation $e^+e^- \to Z^* \to h_ah_bX$ (including $\gamma$-$Z$ interference) within this model. This is the first time a complete framework has been presented for the examination of TMD FFs within $e^+e^-\to h_ah_bX$. We also specify certain parts of our analysis that hold for the triple-polarized semi-inclusive deep-inelastic scattering process and for di-hadron fragmentation. Furthermore, we give an explicit prescription of how our work can be translated to the Drell-Yan reaction, which provides for the first time full results for double-polarized Drell-Yan that include electroweak effects. We further discuss the relevance of our $e^+e^-\to h_ah_bX$ results for future experiments at $e^+e^-$ machines.