Large-pTprocess in a nonscaling parton model

A nonscaling parton model is proposed to describe the large-transverse-momentum processes in hadron collisions. The scale-noninvariance behavior of the parton momentum distribution is deduced from the recent $\mathrm{ep}$ and $\mu p$ deep-inelastic scattering data where gross violation of scaling has been observed. Power-law-breaking effects are parametrized and utilized in the large-$p_T$ calculations. The basic subprocess in which the large-angle scattering occurs is taken to be between the partons only. With the normalization as the only adjustable parameter in the theory, we have achieved excellent fits of the pion and proton inclusive cross sections at large $p_T$ for various energies. We have also produced a no-parameter fit of the $p_T$ dependence of the opposite-side correlation at 90°. We predict a dip at $y=0\mathrm{}$ in the rapidity distribution at high $p_T$ in the opposite hemisphere, but no data with $p_T>2\mathrm{}$ GeV/c are available to check the prediction. The phenomenological success of the nonscaling model therefore on the one hand restores the quark-quark hard-collision subprocess for large-$p_T$ reactions, while on the other suggests severe deviation from scaling in lepton-induced interactions at very high $Q^2$.