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Abstract

The ivp elastic scattering analyzing powers were measured across the energies spanning the A(1232) resonance. This work presents 7r+ data at the pion kinetic energies 117, 130, 139, 155, 169, 180, 193, 218, 241 and 267 MeV and ir~ data at the energies 87, 117, 193 and 241 MeV. The Canadian High Acceptance Orbit Spectrometer (CHAOS), which consists of tracking chambers and particle identification counters in a vertical magnet field geometry, was used for all the measurements. A dedicated, spin polarized, butanol target was employed in frozen spin mode. The 360° acceptance of the CHAOS spectrometer allowed a novel analysis technique that avoided the systematic errors normally associated with beam counting. Persistent target problems did not allow this experiment to measure exclusively at energies below 140 MeV as intended, and forced the use of previously measured analyzing power data in order to obtain an absolute calibration of the target polarization. A new measurement technique was employed, in which the beam energy was varied while maintaining the target polarization. This resulted in sets of analyzing powers at several energies that have no independent systematic error but only an overall normalization correction. A single-energy phase shift analysis using the Karlsruhe PHASAN program showed that the 'canonical' S-wave phase shifts of the KH80 analysis are not well determined at the energies covered by this work. The present results favor the phase shifts obtained by the VPl group (SM95) and hence supports their (lower) value for the pion-nucleon coupling constant glNN/4.ir = 13.7 ± 0.1. Due to the dominance of the P33 partial wave in this energy region, the analyzing powers can not discriminate between the various inconsistent sets of differential cross sections that at present hinder the extraction of fundamental parameters of QCD, such as the pion-nucleon cr-term.