Chiral extrapolation of lattice data for heavy baryons

Abstract

The masses of heavy baryons containing a b quark have been calculated numerically in lattice QCD with pion masses which are much larger than the physical value. In the present work we extrapolate these lattice data to the physical mass of the pion by applying an effective chiral Lagrangian for heavy baryons, which is invariant under chiral symmetry when the light quark masses go to zero and heavy quark symmetry when the heavy quark masses go to infinity. A phenomenological functional form with three parameters, which has the correct behavior in the chiral limit and appropriate behavior when the pion mass is large, is proposed to extrapolate the lattice data. It is found that the extrapolation deviates noticeably from the naive linear extrapolation when the pion mass is smaller than about 500 MeV. The mass differences between Σb and Σb* and between Σb(*) and Λb are also presented. Uncertainties arising from both lattice data and our model parameters are discussed in detail. We also give a comparison of the results in our model with those obtained in the naive linear extrapolations.