Flavor-Spin Symmetry Estimate of the Nucleon Tensor Charge

Abstract

The axial vector and tensor charge, defined as the first moments of the forward nucleon matrix elements of corresponding quark currents, are essential for characterizing the spin structure of the nucleon. However, the transversity distribution and thus the tensor charge decouple at leading twist in deep inelastic scattering, making them hard to measure. Additionally, the non-conservation of the tensor charge makes it difficult to predict. There are no definitive theoretical predictions for the tensor charge, aside from several model dependent calculations. We present a new approach that exploits the approximate mass degeneracy of the light axial vector mesons ($a_1$(1260), $b_1$(1235) and $h_1$(1170)) and uses pole dominance to calculate the tensor charge. The result is simple in form. It depends on the decay constants of the axial vector mesons and their couplings to the nucleons, along with the average transverse momentum of the quarks in the nucleon.