Nankai Univ, Dept Phys, Tianjin 300071, Peoples R China
; Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
; Natl Lab Heavy Ion Accelerator, Ctr Theoret Nucl Phys, Lanzhou 730000, Peoples R China
; China Ctr Adv Sci & Technol, World Lab, Beijing 100080, Peoples R China
In this work, we evaluate the mass spectra of baryons which consist of two heavy quarks and one light quark in the MIT bag model. The two heavy quarks constitute a heavy scalar or axial-vector diquark. Concretely, we calculate the spectra of |q(QQ('))>(1/2) and |q(QQ('))>(3/2) where Q and Q(') stand for b and/or c quarks. Especially, for |q(bc)>(1/2) there can be a mixing between |q(bc)(0)>(1/2) and |q(bc)(1)>(1/2) where the subscripts 0 and 1 refer to the spin state of the diquark (bc), the mixing is not calculable in the framework of quantum mechanics as the potential model is employed, but can be evaluated by the quantum field theory. Our numerical results indicate that the mixing is sizable.