Low energy πN scattering

The pion-nucleon sigma term is an explicit measure of chiral symmetry breaking in QCD due to the non-zero light quark masses, which can be used to probe the strange sea quark content of the proton. A review of the experiments which determine Sigma (piN) will be given, focusing on recent work in this area performed at TRIUMF. This includes near threshold pi (+/-)p --> pi (+/-)pi (+)n experiments which provide the most precise measure to date of the I=J=0 pi scattering length a(0)(0), as well as pi (+/-)p elastic scattering differential cross section and analyzing power experiments. The CHAOS group at TRIUMF has recently performed pi (-)p analyzing power measurements through the S-P interference region, down to 51 MeV. Finally, a program of low energy pi (+/-)p differential cross section measurements in the Coulomb-nuclear interference region has begun from which we expect to be able to measure Re(D ($) over bar (+)) at t=0, as well as the S- and P- wave piN scattering lengths a(o+)(+) and a(1+)(+). The connection to Sigma (piN) is made through Re(D ($) over bar (+)) at the Cheng-Dashen point, and the extrapolation to the Cheng-Dashen point is characterized in terms of the threshold parameters a(0+)(+) and a(1+)(+).