Partial conservation of the axial current and axial exchange currents in the nucleon

Abstract

We discuss the axial form factors of the nucleon within the context of the nonrelativistic chiral quark model. Partial conservation of the axial current (PCAC) imposed at the quark operator level enforces an axial coupling for the constituent quarks which is smaller than unity. This leads to an axial coupling constant of the nucleon $g_A$ in good agreement with experiment. PCAC also requires the inclusion of axial exchange currents. Their effects on the axial form factors are analyzed. We find only small exchange current contributions to $g_A$, which is dominated by the one-body axial current. On the other hand, axial exchange currents give sizeable contributions to the axial radius of the nucleon $r_A^2$, and to the non-pole part of the induced pseudoscalar form factor $g_P$. For the latter, the confinement exchange current is the dominant term.

The formal part of the paper developped in sections III and IV has been clearly improved. The numerical results change slightly. A few new references added. Version accepted for publication in Nuclear Physics A

References in corpus (2)

• Axial structure of the nucleon
• Cubic Casimir operator of SU${}_C$(3) and confinement in the nonrelativistic quark model

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