Measurement of polarization parameter P in elastic π+-p scattering in the region of low-lying pion-nucleon resonances

Systematic measurements of a polarization parameter p in elastic π+-p scattering with the error δP=+-(0.05-g.15) in the 450-600 MeV energy range for π-p scattering and 335-580 MeV for π+p scattering are conducted. The experiment is carried out on the π meson beam of the sychrocyclotron using a polarized proton target and wire spark chambers with magnetostriction data output. Application of spark chambers permitted to accurately determine spatial position of trajectory of scattered π- meson and recoil proton and to more effectively exercise suppression of inelastic background by means of kinematic criteria. The obtained data permit to determine angular dependence of the polarization parameter P. New accurate experimental data on polarization parameter P in elastic π-p and π+p scattering at 12 energies in the 300-o00 MeV range (125 experimental points) are obtained. Sharp changes of P parameters in π-p and especially in π+p scattering in the 500-600 MeV energy range for scattering in the rear hemisphere are revealed. The results obtained do not prove predictions of the existing phase analysis in certain regions that testifies to the necessity of conducting a new phase analysis. Further precise investigations of P parameter behaviour in π-p and π+p scattering in the 510-560 MeV range with the step by the energy of 10 MeV or less are of extreme interest because just in this range the P11-S11 and D13 resonances are overlapped stronger, and a new channel π-p → etaeta is open. Determinations of spin rotation parameters R and A in π+-p scattering in the energy range up to 700 MeV are necessary