Particle theory

Abstract:

We show that the contribution of Drell-Yan dynamics to lepton pair production at fixed x, does not scale with energy, but instead decreases as a power of the energy. There is a transition to a different dynamical picture, and the massive photon now probes the quark-antiquark correlation function of the incident hadron, thus providing a unique handle on this quantity. © 1978.

Abstract:

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 ep and μp deep-inelastic scattering data where gross violation of scaling has been observed. Power-law-breaking effects are parametrized and utilized in the large-pT 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 pT for various energies. We have also produced a no-parameter fit of the pT dependence of the opposite-side correlation at 90. We predict a dip at y=0 in the rapidity distribution at high pT in the opposite hemisphere, but no data with pT>2 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-pT reactions, while on the other suggests severe deviation from scaling in lepton-induced interactions at very high Q2. © 1978 The American Physical Society.

Abstract:

Scaling violation in deep inelastic lepton-proton processes is shown to be related to the apparent pT-8 behavior of the large-pT pion inclusive distribution at s>23.5 GeV, within the framework of the quark-quark hard-collision model. Power-law scale-breaking fits of the structure functions as determined by the ep and μp data are used as inputs in our calculations. Excellent agreement with the high-energy data on large-pT pions is obtained in both the energy and xT dependences. No adjustable parameters are used except for one overall normalization. © 1976 The American Physical Society.