  Differential cross sections for pi- p and pi+ p elastic scattering were
measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS
magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon
background suppression, provided simultaneous coverage of a large part of the
full angular range, thus allowing very precise relative cross section
measurements. The absolute normalisation was determined with a typical accuracy
of 5 %. This was verified in a simultaneous measurement of muon proton elastic
scattering. The measured cross sections show some deviations from phase shift
analysis predictions, in particular at large angles and low energies. From the
new data we determine the real part of the isospin forward scattering
amplitude.
