Nucleon Momentum Decomposition in QCD

TL;DR

This paper proposes two gauge-invariant decompositions of nucleon momentum into quark and gluon contributions, predicting different gluon momentum fractions and clarifying issues related to the proton spin crisis.

Contribution

It introduces two theoretically consistent decompositions of nucleon momentum based on gauge-invariant quark canonical momentum, addressing existing confusions.

Findings

Gluons carry either 6% or 21% of nucleon momentum.

Clarifies the physical implications for the proton spin crisis.

Provides a framework for understanding nucleon momentum decomposition.

Abstract

~Based on the gauge invariant quark canonical momentum we construct two theoretically possible decompositions of nucleon momentum to those of quarks and gluons. We predict that either 6% or 21% of nucleon momentum is carried by gluons, depending on what type of gluons are in nucleons. We clarify the existing confusions on this problem and discuss the physical implications of our result on the proton spin crisis problem.