Bethe-Salpeter Equation for Heavy Baryons ω_{Q}^{(*)} in the Diquark Picture

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Abstract
In the heavy quark limit, the heavy baryons \omega_{Q}^{(*)} (\omega could be \Sigma, \Xi or \Omega and Q=b or c) are regarded as composed of a heavy quark and an axial vector, light diquark with good spin and isospin quantum numbers. Based on this diquark picture we establish the Bethe-Salpeter (B-S) equation for \omega_{Q}^{(*)} in the limit where the heavy quark has infinite mass, m_Q -> \infty. It is found that in this limit there are three components in the B-S wave function for \omega_{Q}^{(*)}. Assuming the kernel to consist of a scalar confinement term and a one-gluon-exchange term we derive three coupled integral equations for the three B-S scalar functions in the covariant instantaneous approximation. Numerical solutions for the three B-S scalar functions are presented, including a discussion about their dependence on the various input parameters. These solutions are applied to calculate the Isgur-Wise functions \xi (\omega) and \zeta (\omega) for the weak transitions \Omega_{b}^{(*)} \to \Omega_{c}^{(*)}. Using these we give predictions for the Cabibbo-allowed nonleptonic decay widths and up-down asymmetries for \Omega_{b} \to \Omega_{c}^{(*)} plus a pseudoscalar or vector meson.

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