New Result for the Pion-Nucleon Sigma Term from an Updated VPI/GW Pion-Nucleon Partial-Wave and Dispersion Relation Analysis
Abstract
A new result for the nucleon sigma term from an updated pion-nucleon partial-wave and dispersion relation analysis of the Virginia Polytechnic Institute (now George Washington University) group is discussed. Using a method similar to that of Gasser, Leutwyler, Locher, and Sainio, we obtain Sigma=90 +/- 8 MeV (preliminary), in disagreement with the canonical result 64 +/- 8 MeV, but consistent with expectations based on new information on the πNN coupling constant, pionic atoms, and the Delta resonance width.
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