E2/M1 ratio from the Mainz p(γ⃗,p)π0p(\vec \gamma, p)\pi^0 data

We suggest that the error quoted in the Mainz determination of the E2/M1 ratio (at the resonance energy) should be enlarged. A term dropped in expressions used by this group could be significant.Comment: 2 pages of text. Submitted to the Comments section of PR

Single-channel fits and K-matrix constraints

A K-matrix formalism is used to relate single-channel and multi-channel fits. We show how the single-channel formalism changes as new hadronic channels become accessible. These relations are compared to those commonly used to fit pseudoscalar meson photoproduction data.Comment: 9 pages, 2 figures. A numerical example has been adde

Comment on `Measurement of the π+p⃗\pi^+ \vec p analyzing power at 68.3 MeV'

We comment on a recent paper by Weiser et al. [Phys. Rev. C {\bf 54}, 1930 (1996)]. The authors have performed a single-energy analysis of $\pi^+ p$ scattering data at 68.3 MeV, finding a value for the $S_{31}$ phase shift about 1^o smaller than found in the Karlsruhe-Helsinki (KH) partial-wave analysis. The authors use this result to argue for a dispersion relation analysis using recently measured data, so that their effect on the $\pi NN$ coupling constant (f^2) and $\Sigma$ amplitude can be determined. We note that these tasks were accomplished prior to the submission of the above paper. We clarify the effect of this new analyzing power data on f^2 and the $\Sigma$ amplitude.Comment: 5 pages of text. Revised according to Referee suggestion

Correlations of πN\boldsymbol{\pi N} Partial Waves for Multi-Reaction Analyses

In the search for missing baryonic resonances, many analyses include data from a variety of pion- and photon-induced reactions. For elastic $\pi N$ scattering, however, usually the partial waves of the SAID or other groups are fitted, instead of data. We provide the partial-wave covariance matrices needed to perform correlated $\chi^2$ fits, in which the obtained $\chi^2$ equals the actual $\chi^2$ up non-linear and normalization corrections. For any analysis relying on partial waves extracted from elastic pion scattering, this is a prerequisite to assess the significance of resonance signals and to assign any uncertainty on results. The influence of systematic errors is also considered.Comment: 7 pages, 3 figures; Acknowledgements update