{"paper":{"title":"The pion-nucleon $\\sigma$ term from pionic atoms","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["hep-ph","nucl-ex"],"primary_cat":"nucl-th","authors_text":"A. Gal, E. Friedman","submitted_at":"2019-01-10T12:41:34Z","abstract_excerpt":"Earlier work suggested that the in-medium $\\pi N$ threshold isovector amplitude $b_1(\\rho)$ gets renormalized in pionic atoms by about 30% away from its $\\rho=0$ free-space value, relating such renormalization to the leading low-density decrease of the in-medium quark condensate $<\\bar q q>$ and the pion decay constant $f_{\\pi}$ in terms of the pion-nucleon $\\sigma$ term $\\sigma_{\\pi N}$. Accepting the validity of this approach, we extracted $\\sigma_{\\pi N}$ from a large-scale fit of pionic-atom level shift and width data across the periodic table. Our fitted value $\\sigma_{\\pi N}=57\\pm 7$ MeV"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1901.03130","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}