R-Matrix Calculations for Few-Quark Bound States
  The R--matrix method is implemented to study the heavy charm and bottom diquark, triquark, tetraquark and pentaquarks in configuration space, as the bound states of quark--antiquark, diquark--quark, diquark--antidiquark and diquark--antitriquark systems, respectively. The mass spectrum and the size of these systems are calculated for different partial wave channels. The calculated masses are compared with recent theoretical results obtained by other methods in momentum and configuration spaces and also by available experimental data. 
M. A. Shalchi, M. R. Hadizadeh
hep-ph nucl-th