Excitation spectra of heavy baryons in diquark models

The excitation energy spectra are investigated by using diquark models in order to discuss the possibility of the existence of the diquark as a constituent of the single heavy baryons. We consider two diquark models in which the diquark is treated as a constituent of baryons together with a heavy baryon. In model A the diquark is a point-like particle, while it is a spatially extended object in model B. We determine the masses of scalar and axial vector diquarks by the ground state masses of the charmed baryons. We find that both models reproduce well the excitation energy spectra of the charmed and bottomed baryons, whereas the string tension of the confinement potential in model A should be a half of that of the charmonium and Model B overestimates the 2s excitation energy.