arXiv subjects
Publications and source records attributed to Barry R. Holstein.
Recently methods have been developed which exploit the chiral symmetry of QCD in order to make rigorous contact with low energy particle physics phenomenology. In these lectures we present a pedagogical introduction to these techniques.
This paper gives an overview of a Workshop on Chiral Dynamics: Theory and Experiment which was held at MIT July 25-29, 1994; its unique feature was the equal mixture of theory and experiment. The purpose of the workshop was to bring together many of the active participants to assess the status of the field and to explore fruitful future directions. The foundations and present status of the theory were reviewed as well as the experimental status of the field. To facilitate the discussion of future directions working groups were organized on Threshold Photo/Electropion Production, Two-Pion Threshold and the Chiral Anomaly, Nucleon Polarizabilities, Pion and Sigma Polarizabilities, $π-π$ Interactions, and $π$-N Interactions; these subjects were the focus of the experimental aspects of the workshop.
Symmetry tests provide an important probe for the structure of elementary particle interactions and for the validity of the standard model. However, it is pointed out that in the interpretation of such experiments one must keep in mind that in many cases apparent "violations" of such tests are actually the result of ordinary effects within the standard model.
We examine mass-corrected SU(6) symmetry predictions in the quark model relating vector, axial-vector and strong NN and NΔcouplings, and demonstrate that the experimental NΔvalue is significantly higher than predicted in each case. Nevertheless the Goldberger-Treiman relation is satisfied in both sectors. Possible origins of the discrepancy of the quark model predictions with experiment are discussed.
Recent experimental results on the proton and neutron polarizabilities are examined from the point of view of backward dispersion relations. Results are found to be in reasonable agreement with the measured values. A rigorous relationship between the nucleon and pion polarizabilities is derived and shown to be in excellent agreement with several models.
Recently the development of chiral perturbation theory has allowed the generation of rigorous low-energy theorems for various hadronic processes based only on the chiral invariance of the underlying QCD Lagrangian. Herein we examine the experimental implications of chiral symmetry in the regime of electroweak Goldstone boson interactions. Contribution to BNL Hadronic Beam Physics Workshop.
Recent attempts to detect the pion polarizability via analysis of $γγ\rightarrowππ$ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement.