Excitation spectra of heavy baryons in diquark models

Abstract

Abstract The excitation energy spectra of heavy baryons consisting of a heavy quark and two light quarks are investigated using diquark models in order to examine the nature of the diquark as a constituent of single heavy baryons. We consider two diquark models; in Model A the diquark is treated as a point-like particle, while it has a spatial size in Model B. We determine the masses of scalar and axial vector diquarks by the mass difference of the ground-state charmed baryons and the Λc baryon, while the mass of the ud scalar diquark in the Λc baryon is assumed to be 500 MeV as a reference. The parameters of these models are fixed by the 1p excitation energy of Λc. We find that Model A reproduces well the excitation energy spectra of the charmed and bottomed baryons, although the string tension of the confinement potential in Model A should be half of that of the charmonium, while Model B suggests degeneracy of the 2s and 1d states, which is not seen in the Λc spectrum.