Quantum-chromodynamic predictions for large-pThadron production with transversely polarized beam and target

We apply a hard-scattering model based on quantum-chromodynamic perturbation theory to the production of hadrons at large transverse momentum by transversely polarized beam and target protons. We find that, at large $x_T=\frac{2p_T}{\sqrt{s}}$, the spin-spin asymmetry $A_{\mathrm{NN}}$ for the case of transversely polarized protons is significantly smaller than the corresponding asymmetry $A_{\mathrm{LL}}$ for longitudinally polarized protons. This situation is due to the relatively smaller size of both the quark-quark scattering asymmetry and the spin-dependent distribution functions for quarks in the transversely polarized proton.