{"paper":{"title":"Precision spectroscopy of pionic 1s states of Sn nuclei and evidence for partial restoration of chiral symmetry in the nuclear medium","license":"","headline":"","cross_cats":["nucl-th"],"primary_cat":"nucl-ex","authors_text":"A. Gillitzer, G. M\\\"unzenberg, H. Geissel, H. Gilg, H. Weick, K. Itahashi, K. Suzuki, M. Fujita, M. Iwasaki, M. Matos, M. Sato, M. Shindo, M. Winkler, P. Kienle, R.S. Hayano, S. Hirenzaki, T. Ohtsubo, T. Suzuki, T. Yamazaki, T. Yoneyama","submitted_at":"2002-11-21T13:19:15Z","abstract_excerpt":"Deeply bound 1s states of $\\pi^-$ in $^{115,119,123}$Sn were preferentially observed using the Sn($d$,$^3$He) pion-transfer reaction under the recoil-free condition. The 1s binding energies and widths were precisely determined, and were used to deduce the isovector parameter of the s-wave pion-nucleus potential to be $b_1 =-0.115\\pm 0.007 ~m_{\\pi}^{-1}$. The observed enhancement of $|b_1|$ over the free $\\pi N$ value ($b_1^{\\rm free}/b_1 = 0.78 \\pm 0.05$) indicates a reduction of the chiral order parameter, $f^{*}_{\\pi} (\\rho)^2/f_{\\pi}^2 \\approx 0.64$, at the normal nuclear density, $\\rho = \\"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"nucl-ex/0211023","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":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/nucl-ex/0211023/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"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"}