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The in-medium isovector pi N amplitude from low energy pion scattering

E. Friedman·M. Bauer·J. Breitschopf·H. Clement·H. Denz·E. Doroshkevich·A. Erhardt·G. J. Hofman·R. Meier·G. J. Wagner·G. Yaari
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Abstract

Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.

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E. Friedman, M. Bauer, J. Breitschopf, H. Clement, H. Denz, E. Doroshkevich, A. Erhardt, G. J. Hofman, R. Meier, G. J. Wagner, G. Yaari. 2004-08-04. The in-medium isovector pi N amplitude from low energy pion scattering. https://doi.org/10.1103/physrevlett.93.122302

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