Test of isospin symmetry via low energy $^1$H($π^-$,$π^o$)$n$ charge exchange

Abstract

We report measurements of the $π^- p \to π^o n$ differential cross sections at six momenta (104-143 MeV/c) and four angles (0-40 deg) by detection of $γ$-ray pairs from $π^o \to γγ$ decays using the TRIUMF RMC spectrometer. This region exhibits a vanishing zero-degree cross section from destructive interference between s-- and p--waves, thus yielding special sensitivity to pion-nucleon dynamics and isospin symmetry breaking. Our data and previous data do not agree, with important implications for earlier claims of large isospin violating effects in low energy pion-nucleon interactions.

5 pages, 3 figures, submitted to Physical Review Letters