QCD Sum Rule for 1/2- Baryons
  The masses of the flavor octet and singlet baryons with negative parity and spin 1/2 are calculated using the QCD sum rule. We find that the chiral symmetry breaking vacuum condensates cause the mass splitting of the positive and negative baryons. The present sum rule reproduces the observed masses of these baryons within 10%, and predicts the mass of the excited Xi baryon with $J^P = {1/2}^{-}$ at 1.63 GeV. We confirm that the negative-parity state, $\Lambda_S-$, is the ground state in the flavor singlet baryon spectrum. 
D. Jido and M. Oka (Tokyo Inst. of Tech.)