Measurements of spin rotation parameter A in pion–proton elastic scattering at 1.62 GeV/c

Abstract

The ITEP-PNPI collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at P beam = 1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared to the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.PACS number(s) : 13.75. Gx, 13.85.Dz, 13.88.+e.

P -wave excited baryons from pion- and photo-induced hyperon production

“…But this analysis challenges the existence of many resonances. A strong argument in favor of the Arndt analysis is the correct prediction of spin rotation parameters [14,15,16] and of the backward asymmetry [17] in the elastic pion-proton scattering from ITEP/PNPI while the predictions from [1,2] show clear discrepancies with the data. On the other hand, it is difficult to believe that the consistency between the older analyses is just fortuitous.…”

Spectroscopy of baryon resonances

“…The latter analysis included high precision data from the meson factories (see [34] for a list of data). This analysis predicted the spin rotation parameters [35][36][37] and the backward asymmetry [38] in the elastic pion-proton scattering from ITEP/PNPI very precisely while the predictions from [32,33] show clear discrepancies with the data. Hence the number of trustworthy resonances was reduced to 11 N * and 9 Δ * only.…”

Partial wave analysis

“…This latter analysis included high precision data from the meson factories at LAMPF, PSI, and TRIUMF. A strong argument in favor of the Arndt et al analysis was the correct prediction of spin rotation parameters [16][17][18] and of the backward asymmetry [19] in the elastic pionproton scattering from ITEP/PNPI; the predictions from [11,12] show clear discrepancies with the data.…”