Markov-Yukawa transversality on covariant null-plane: Baryon form factor and magnetic moments

Abstract

The baryon-qqq vertex function governed by the Markov-Yukawa Transversality Principle (MY TP), is formulated via the Covariant Null-Plane Ansatz (CNPA) as a 3-body generalization of the corresponding qq̅ problem, and employed to calculate the proton e.m. form factor and baryon octet magnetic moments.The e.m. coupling scheme is specified by letting the e.m. field interact by turn with the "spectator" while the two interacting quarks fold back into the baryon. The S₃ symmetry of the matrix element is preserved in all d.o.f.'s together. The CNPA formulation ensures, as in the qq̅ case, that the loop integral is free from the Lorentz mismatch disease of covariant instantaneity (CIA), while the simple trick of 'Lorentz completion' ensures a Lorentz invariant structure. The k^-4 scaling behaviour at large k² is reproduced. And with the infrared structure of the gluonic propagator attuned to spectroscopy, the charge radius of the proton comes out at 0.96fm. The magnetic moments of the baryon octet, also in good accord with data, are expressible as (a+bλ)/(2+λ), where a, b are purely geometrical numbers and λ a dynamics-dependent quantity.