Baryon fields withUL(3)×UR(3)chiral symmetry. III. Interactions with chiral[(3,3¯)⊕(3¯,3)]spinless mesons

Abstract

Three-quark nucleon interpolating fields in QCD have well-defined SU_L(3)*SU_R(3) and U_A(1) chiral transformation properties, viz. [(6,3)+(3,6)], [(3,3_bar)+(3_bar,3)], [(8,1)+(1,8)] and their "mirror" images, Ref.[9]. It has been shown (phenomenologically) in Ref.[3] that mixing of the [(6,3)+(3,6)] chiral multiplet with one ordinary ("naive") and one "mirror" field belonging to the [(3,3_bar)+(3_bar,3)], [(8,1)+(1,8)] multiplets can be used to fit the values of the isovector (g_A^3) and the flavor-singlet (isoscalar) axial coupling (g_A^0) of the nucleon and then predict the axial F and D coefficients, or vice versa, in reasonable agreement with experiment. In an attempt to derive such mixing from an effective Lagrangian, we construct all SU_L(3)*SU_R(3) chirally invariant non-derivative one-meson-baryon interactions and then calculate the mixing angles in terms of baryons' masses. It turns out that there are (strong) selection rules: for example, there is only one non-derivative chirally symmetric interaction between J=1/2 fields belonging to the [(6,3)+(3,6)] and the [(3,3_bar)+(3_bar,3)] chiral multiplets, that is also U_A(1) symmetric. We also study the chiral interactions of the [(3,3_bar)+(3_bar,3)] and [(8,1)+(1,8)] nucleon fields. Again, there are selection rules that allow only one off-diagonal non-derivative chiral SU_L(3)*SU_R(3) interaction of this type, that also explicitly breaks the U_A(1) symmetry. We use this interaction to calculate the corresponding mixing angles in terms of baryon masses and fit two lowest lying observed nucleon (resonance) masses, thus predicting the third (J=1/2, I=3/2) Delta resonance, as well as one or two flavor-singlet Lambda hyperon(s), depending on the type of mixing. The effective chiral Lagrangians derived here may be applied to high density matter calculations.