Size and scaling of the double-helicity-flip hadronic structure function

Recently, Jaffe and Manohar identified a new leading-twist structure function $\Delta (x,Q^2)$, which can be measured in deep-inelastic scattering from polarized targets with spin ≥1. We calculate the scaling behavior of $\Delta (x,Q^2)$ in QCD, both by computing the anomalous dimensions of the associated operators and by finding the splitting function for the appropriate parton density. We also estimate the size of the lowest moment of $\Delta (x,Q^2)$ in the bag model. In an appendix we give the complete cross section for electroproduction from a spin-1 target of arbitrary polarization.