Transverse spin in QCD and transverse polarized deep inelastic scattering

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.

Gravitational form factors and transverse spin sum rule in a light front quark-diquark model in AdS/QCD

“…For the nucleons, q can be either up (u) or down(d) quark. The functions ϕ (1) q (x, k ⊥ ) and ϕ (2) q (x, k ⊥ ) are the wave functions predicted by soft-wall AdS/QCD [13]…”

“…For a massive particle like nucleon, the intrinsic spin operators can be related with the Pauli-Lubanski operators through the following relations [1,2,10],…”

Twist-three relations of gluonic correlators for the transversely polarized nucleon

“…Just as the integral of g T (x) gives the quark helicity ∆q, we show that the first moment of the twistthree distribution G 3T (x) is equal to the usual gluon helicity contribution ∆G to the nucleon spin. We will further discuss the implication of this result through an analysis based on the Pauli-Lubansky vector [25,26] and the newly proposed decomposition scheme of the nucleon spin [27][28][29].…”

Physics at the light-front

“…See for example, Refs. [33,5,34,31,35]. The projection J z is kinematical and is conserved separately for each Fock component: each light-front Fock wavefunction satisfies the sum rule:…”