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

A precision measurement of absolute ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ elastic differential cross sections at incident pion laboratory kinetic energies from ${T}_{\ensuremath{\pi}}=141.15$ to 267.3 MeV is described. Data were obtained detecting the scattered pion and recoil proton in coincidence at 12 laboratory pion angles from $55\ifmmode^\circ\else\textdegree\fi{}$ to $155\ifmmode^\circ\else\textdegree\fi{}$ for ${\ensuremath{\pi}}^{+}p$ and six angles from $60\ifmmode^\circ\else\textdegree\fi{}$ to $155\ifmmode^\circ\else\textdegree\fi{}$ for ${\ensuremath{\pi}}^{\ensuremath{-}}p.$ Single arm measurements were also obtained for ${\ensuremath{\pi}}^{+}p$ energies up to 218.1 MeV, with the scattered ${\ensuremath{\pi}}^{+}$ detected at six angles from $20\ifmmode^\circ\else\textdegree\fi{}$ to $70\ifmmode^\circ\else\textdegree\fi{}.$ A flat-walled, supercooled liquid hydrogen target and solid ${\mathrm{CH}}_{2}$ targets were used. The data are characterized by small uncertainties, $\ensuremath{\sim}1--2%$ statistical and $\ensuremath{\sim}1--1.5%$ 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.

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