A Primer on Partial Wave Analysis
  In the 90s of the last century high statistics experiments with fully equipped 4$\pi$ detectors have lead to a better insight in the spectrum of hadrons. In particular the finding of crypto-exotic and $J^{PC}$ exotic states tremendously improved the experimental situation in meson spectroscopy. All this was possible only with sophisticated analysis methods like the decomposition of measured phase-space distribution into partial waves and to express the partial waves in terms of complicated dynamical functions. This paper gives an introduction about the concepts and formalisms involved. 
Klaus Peters