Quark Contributions to the Proton Spin and Tensor Charge

Abstract

I calculate the quark contributions to the axial and tensor charges and the spin structure of the proton. The result indicates that the valence current quark spins carry 1/3 of the proton spin, the total contribution of quark spins to the proton spin satisfies $\Delta \Sigma = 1/3 + \Delta \Sigma_{sea} \le 1/3$, and the quarks (their spin plus orbital contributions) contribute about one half of the proton spin at scale of 1 $GeV$. The valence current quark contributions to the proton tensor charge are also obtained.