Tensor-polarized quark and antiquark distribution functions in a spin-one hadron

It is becoming crucial to understand orbital-angular-momentum contributions for clarifying the nucleon-spin issue in the parton level. Twist-two structure functions b(1) and b(2) for spin-one hadrons could probe orbital-angular-momentum effects, which reflect a different aspect from current studies for the spin-1/2 nucleon. The structure functions b(1) and b(2) are described by tensor-polarized quark and antiquark distributions delta(T)q and delta(T)(q) over bar. Using HERMES data on the b(1) structure function for the deuteron, we made an analysis of extracting the distributions delta(T)q and delta(T)(q) over bar in a simple x-dependent functional form. Optimum distributions are proposed for the tensor-polarized valence and antiquark distribution functions from the analysis. A finite tensor polarization is obtained for antiquarks if we impose a constraint that the first moments of tensor-polarized valence-quark distributions vanish.