Electro and Photoproduction of Kaon and Eta Mesons

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

This is a request for support for research on predicting spin observables in the photo- and electro-production of mesons. Our goal continues to be to use the new and precise cross-section and spin observable data, from Je.erson Laboratory (JLAB) and from other GeV electron beam facilities, to determine the fundamental mechanisms of electromagnetic meson production and the associated dynamics of excited nucleons, and perhaps the nature of hadrons themselves. Knowledge of nucleon excited states and their form factors provides important information about the non-perturbative regime of QCD. The photo- and electro-production of p, ., kaon, and vector mesons are being measured with high precision using the impressive JLAB large angle spectrometer (CLAS) detector and the high resolution magnetic spectrometers in Halls A& C. Polarized targets and beams at JLAB and at other facilities allow a variety of single and double spin observables to be measured. Our focus is on the questions: Can we develop a analysis tool that can be used to extract reliable isobar information from electromagnetic production experiments? What can one learn from such measurements? Can quark dynamics be incorporated into the coupled-channels approach we have developed over the last several years? Does evidence exist for the excitation of unusual baryon states and/or those predicted by quark models? The hope is to answer such questions by examining the sensitivity of beam, target, and recoil-particle cross-sections and spin-observables to underlying resonances, t- and u-channel exchanges, and to threshold e.ects. In earlier publications, we deduced general features of spin observables for 0-(p, .,K) and 1-(., ., f) meson production, which are helpful guides in amplitude analyses, model calculations and in planning experiments. We have been combining such insights with viable dynamical coupled-channels(CC) calculations, for which collaborations with Saclay and Argonne National Laboratory have been established and hopefully will continue. The codes we have developed provide .exible, dynamical (o.-shell) methods for including important spin-dependent .nal state interactions along with threshold, cusp, and isobar excitation e.ects. Recently, we .gured out how to incorporate quark model dynamics. Developing this code has been a slow process, but we are now ready to apply this project to recent data and to extend the research to a wider range of mesons and to electroproduction.