Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling

TL;DR

This paper develops a relativistic light-front framework for pion loop corrections to nucleon-photon interactions, ensuring gauge invariance, and applies it to analyze chiral effects on nucleon structure functions.

Contribution

It introduces a relativistic light-front approach to pion loop corrections, addressing gauge invariance and resolving a longstanding puzzle in pion cloud contributions.

Findings

Verified gauge invariance and Ward-Takahashi identities at all orders.

Computed chiral corrections to matrix elements of local operators.

Resolved discrepancies between pseudovector and pseudoscalar coupling calculations.

Abstract

We present a relativistic formulation of pion loop corrections to the coupling of photons with nucleons on the light-front. Vertex and wave function renormalization constants are computed to lowest order in the pion field, including their nonanalytic behavior in the chiral limit, and studied numerically as a function of the ultraviolet cutoff. Particular care is taken to explicitly verify gauge invariance and Ward-Takahashi identity constraints to all orders in the m_pi expansion. The results are used to compute the chiral corrections to matrix elements of local operators, related to moments of deep-inelastic structure functions. Finally, comparisons of results for pseudovector and pseudoscalar coupling allows the resolution of a long-standing puzzle in the computation of pion cloud corrections to structure function moments.