R. L. Jaffe
Published 2001-08-02, updated 2002-01-03Version 2
The nucleon's axial vector charge, g_A, becomes delocalized in the chiral limit. When m_\pi = 0, and SU(2)_L x SU(2)_R is exact, 1/3 of the nucleon's axial charge is to be found at infinite distance from the nucleon. For finite m_\pi this result is approached smoothly as m_\pi -> 0. We illustrate this effect by considering the lepton-proton spin-spin interaction arising from Z^0 exchange as a function of m_\pi. Delocalization may have implications for lattice calculations of g_A and in nuclei.
Comments: Revised content: Further explanation of the limit m_pi -> 0 and an example of a physical process (spin-spin interaction in a hydrogenic atom mediated by Z^0 exchange) which can, in principle, measure the delocalization of g_A. Ten pages using RevTeX; email correspondence to R.L. Jaffe <jaffe@mit.edu>
Journal: Phys.Lett. B529 (2002) 105-110
The chiral limit of QCD and above
Chiral quarks, chiral limit, nonanalytic terms and baryon spectroscopy
New insight on the quark condensate beyond chiral limit
