Analysis of the Low-Energy π-p Elastic-Scattering Data

We report the results of a phase-shift analysis (PSA) of the low-energy elastic-scattering data. Following the method which we had set forth in our previous PSA, we first investigate the self-consistency of the low-energy elastic-scattering databases, via two separate analyses of (first) the pi+ p and (subsequently) the pi- p elastic- scattering data. There are two main differences to our previous PSA: 1) we now perform only one test for the acceptance of each data set (based on its contribution to the overall chi-squared) and 2) we adopt a more stringent acceptance criterion in the statistical tests. We show that it is possible to obtain self-consistent databases after removing a very small amount of the data (4.57% of the initial database). We subsequently fit the ETH model [38] to the truncated elastic-scattering databases. The model-parameter values show reasonable stability when subjected to different criteria for the rejection of single data points and entire data sets. Our result for the pseudovector coupling constant is 0.0726 +- 0.0014. We extract the scattering lengths and volumes, as well as the s- and p-wave hadronic phase shifts up to T = 100 MeV. Large differences in the s-wave part of the interaction can be seen when comparing our hadronic phase shifts with the current SAID solution (WI08); there is general agreement in the p waves, save for the P11 hadronic phase shift