Low energy analyzing powers in pion–proton elastic scattering

Abstract

Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π + p scattering, and at 67.3 and 87.2 MeV for π − p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

Extended partial-wave analysis ofπNscattering data

“…Further low-energy additions include 25 π + p and 3 π − p A y data between 50 and 130 MeV, at medium scattering angles, measured at PSI [16]. New total cross sections for charge-exchange measurements between 40 and 250 MeV came from PSI recently [17].…”

Absorptive Part of Meson–baryon Scattering Amplitude and Baryon Polarization in Chiral Perturbation Theory

“…They are given by (12), with the appropriate changes in flavor, momentum, and spin variables. With (11) and (14), we can rewrite (13) in the more compact form…”

“…There exists, for instance, a substantial body of data on analyzing powers in nucleon-pion scattering at energies around the ∆ resonance peak (see [9,10,11] and refs. therein), and at lower energies [12,13]. In the strange sector data on spin observables at low energies are definitely rare, though some exist [14].…”

Baryon polarization in low-energy unpolarized meson-baryon scattering

“…Dashed lines: fit I, solid lines: fit II. Data from[59,60,61], after sign flipping. (See main text for explanation of fits and sign convention.)…”

“…(See main text for explanation of fits and sign convention.) For data from[61], statistical and systematic errors added in quadrature.…”