The heavy mesons in Nambu--Jona-Lasinio model
  We propose an extended Nambu--Jona-Lasinio model to include the heavy mesons with the heavy quark symmetry. The quark current-current interaction is generalized to include the heavy quark currents. In order to comply with the heavy quark spin symmetry at the heavy quark limit, the quark mass dependence of the interaction strength is introduced. The light and heavy pseudo-scalar and vector meson, their masses and the weak decay constants, are calculated in the unified frame. 
Xiao-Yu Guo, Xiao-Lin Chen, and Wei-Zhen Deng
hep-ph