The Origin of the Nucleon Mass

Abstract

It is often claimed that 98% of the nucleon mass is generated by quantum chromodynamics. The decomposition of the nucleon mass based on the trace of the energy-momentum tensor suggests that gluons play by far a dominant role. About 25 years ago, Ji proposed another decomposition based on the energy component of the energy-momentum tensor, leading to a quite different picture. Recently, we critically revisited these decompositions and argued that both overlooked pressure effects. In particular we showed that Ji's decomposition, although mathematically correct, makes little sense from a physical point of view. We identify the proper mass decomposition along with a balance equation for the pressure forces.

Mass sum rule of hadrons in the QCD instanton vacuum

“…This notwithstanding, a specific and physically motivated proposal to budget the mass, was put forth by Ji in [9,26], and since revisited by many [27,28] (and references therein). The ensuing mass composition involves the sum of partonic contributions, some of which may be measurable using DIS experiments.…”