A Leading Order QCD Computation of ππ Elastic Scattering

Citation

Kanwal, Sarbmeet Singh (1983) A Leading Order QCD Computation of ππ Elastic Scattering. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/7xbf-c510. https://resolver.caltech.edu/CaltechTHESIS:10172019-165231405

Abstract

This thesis presents the results of a detailed computation of the leading order scattering amplitude and cross-section for the elastic reaction π⁺π⁺ → π⁺π⁺, in the context of the quark model and perturbative QCD. The calculation is based on the recently demonstrated applicability of QCD-factorization and the renormalization group to exclusive hadronic processes at large momentum-transfers. We show that a large fraction of the hard subprocess diagrams have a pinch singularity in them, which means that the amplitude resulting from these diagrams cannot be proved to be short-distance dominated. This contribution to the scattering amplitude is computed separately and, even after including a Sudakov factor, it is shown to be comparable in magnitude to the hard-scattering contribution. We calculate the energy and angular dependence of the pinch contribution and point out that some of the systematic deviations from power-law scaling, observed in high-P_T meson-baryon and baryon-baryon elastic scattering data, can be explained by assuming that the cross-section for these reactions is dominated by pinch, rather than hard, effects. By normalizing the pion distribution amplitude with the help of the pion decay constant, we have also determined the absolute normalization of the ππ elastic cross-section.

Thesis Files