Do Gluons Carry Half of the Nucleon Momentum?

TLDR

The study investigates whether gluons carry about half of the nucleon momentum in the asymptotic limit. The authors propose testing the revised gluon momentum fraction using novel parton distribution functions. They find that the previously reported half‑momentum fraction arises from an improper definition, and that a gauge‑invariant definition yields only about one‑fifth, implying a need to revisit the nucleon spin structure in the asymptotic limit.

Abstract

We examine the conventional picture that gluons carry about half of the nucleon momentum in the asymptotic limit. We show that this large fraction is due to an unsuitable definition of the gluon momentum in an interacting theory. If defined in a gauge-invariant and consistent way, the asymptotic gluon momentum fraction is computed to be only about one-fifth. This result suggests that the asymptotic limit of the nucleon spin structure should also be reexamined. A possible experimental test of our finding is discussed in terms of novel parton distribution functions.