Unravelling the physical meaning of the Jaffe-Manohar decomposition of the nucleon spin

TL;DR

This paper clarifies the physical interpretation of the Jaffe-Manohar nucleon spin decomposition, emphasizing that it does not directly correspond to the partonic picture and reflects the intrinsic orbital angular momentum structure.

Contribution

It reveals that the Jaffe-Manohar decomposition is not a partonic decomposition and clarifies its true physical meaning related to the nucleon's intrinsic orbital angular momentum.

Findings

Jaffe-Manohar decomposition does not match the partonic picture.

The decomposition reflects the intrinsic orbital angular momentum of the nucleon.

Clarifies misconceptions about the physical meaning of the decomposition.

Abstract

A general consensus now is that there are two physically inequivalent complete decompositions of the nucleon spin, i.e. the decomposition of the canonical type and that of mechanical type. The well-known Jaffe-Manohar decomposition is of the former type. Unfortunately, there is a wide-spread misbelief that this decomposition matches the partonic picture, which states that motion of quarks in the nucleon is approximately free. In the present monograph, we reveal that this understanding is not necessarily correct and that the Jaffe-Manohar decomposition is not such a decomposition, which natively reflects the intrinsic (or static) orbital angular momentum structure of the nucleon.