Transverse Spin in QCD and Transverse Polarized Deep Inelastic Scattering

TL;DR

This paper constructs relativistic transverse spin operators in QCD using light front theory, linking them to transverse polarized deep inelastic scattering and providing new insights into nucleon helicity flip phenomena.

Contribution

It introduces the complete set of transverse spin operators in light front QCD for the first time, advancing understanding of spin structure in relativistic composite systems.

Findings

Transverse spin operators for massless particles are frame-independent.

Established the connection between transverse spin in QCD and polarized deep inelastic scattering.

Discussed implications for nucleon helicity flip and spin structure analysis.

Abstract

We address the long standing problem of the construction of relativistic spin operators for a composite system in QCD. Exploiting the kinematical boost symmetry in light front theory, we show that transverse spin operators for massless particles can be introduced in an arbitrary reference frame, in analogy with those for massive particles. In light front QCD, the complete set of transverse spin operators are identified for the first time, which are responsible for the helicity flip of the nucleon. We establish the direct connection between transverse spin in light front QCD and transverse polarized deep inelastic scattering. We discuss the theoretical and phenomenological implications of our results.