Measurements of the spin rotation parameter A in the elastic pion-proton scattering in the D13(1700) resonance region

The spin rotation parameters A and R were measured for the elastic pion-pro ton scattering by the PNPI-ITEP collaboration in the D-13 (1700) resonance region. The main goal of the experimental program is to resolve the current partial-wave analyses (PWA) uncertainties. Simultaneously with A and R the polarization parameter P was measured with the purpose to improved the exp erimental database and estimate systematic errors. The constraint which dem ands a smooth energy dependence of all pi (-)p transverse amplitude zeros i n the complex plane together with the new experimental data on A parameter can lead to the conclusion that the Barrelet branch of "zero trajectories" is chosen improperly in PWA of the Carnegie-Mellon-Lawrence-Berkely-Laborat ory groups at the range of the pion beam momentum near 1.0 GeV/c. The setup included a longitudinally polarized proton target with superconductive mag net, multiwire spark chambers and carbon polarimeter with thick filter. The experiment was performed at the ITEP proton synchrotron, Moscow.