Composite and elementary natures of a1(1260) meson
  We develop a practical method to analyze the mixing structure of hadrons consisting of two components of quark-composite and hadronic composite. As an example we investigate the properties of the axial vector meson a1(1260) and discuss its mixing properties quantitatively. We also make reference to the large Nc procedure and its limitation for the classification of such a mixed state. 
H. Nagahiro, K. Nawa, S. Ozaki, D. Jido and A. Hosaka
hep-ph