Precision pion-proton elastic differential cross sections at energies spanning the Δ resonance

A precision measurement of absolute, pi (+/-)p elastic differential cross sections at incident pion laboratory kinetic energies from T-pi= 141.15 to 267.3 MeV is described. Data were obtained detecting the scattered, pion and recoil proton in coincidence at 12 laboratory pion angles from 55 degrees to 155 degrees for pi (+) p and six angles from 60 degrees to 155 degrees for pi (-) p. Single arm measurements were also obtained for pi (+) p energies up to 218.1 MeV, with the scattered pi (+) detected at six angles from 20 degrees to 70 degrees. A flat-walled, supercooled liquid hydrogen target and solid CH2 targets were used. The data are characterized by small uncertainties similar to 1-2 % statistical and similar to 1-1.5 % normalization. The reliability of the cross section results was ensured by carrying out the measurements under a variety of experimental conditions to identify and quantify the sources of instrumental uncertainty. Our lowest- and highest-energy data are consistent with overlapping results from TRIUMF and LAMPF In general, the Virginia Polytechnic Institute SM95 partial-wave analysis (PWA) solution describes our data well, but the older Karlsruhe-Helsinki PWA solution KH80 does not.