{"paper":{"title":"50 GeV $\\pi^-$ in, nothing out: a sensitive probe of invisible $\\eta$ and $\\eta'$ decays with NA64h","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":["hep-ph"],"primary_cat":"hep-ex","authors_text":"A. Antonov, A. Celentano, A. E. Karneyeu, A. Marini, A. N. Toropin, A. S. Zhevlakov, A. V. Dermenev, B. Banto Oberhauser, B. Ketzer, B. Radics, D. A. Shchukin, D. Banerjee, D. Cooke, D. V. Kirpichnikov, D. V. Peshekhonov, E. Depero, G. D. Kekelidze, H. Sieber, I. V. Tlisova, I. V. Voronchikhin, J. Bernhard, J. Zamora-Saa, K. M. Salamatin, L. Marsicano, L. Molina Bueno, L. V. Kravchuk, M. A. Ayala Torres, M. Hosgen, M. Mongillo, M. Tuzi, N. Charitonidis, N. V. Krasnikov, O. Soto, P. Bisio, P. Crivelli, P. V. Volkov, R. G. Mena Yanssen, R. Mena Fredes, R. R. Dusaev, S. Girod, S. N. Gninenko, S. V. Donskov, S. V. Gertsenberger, S. V. Kuleshov, T. Enik, V. A. Kachanov, V. A. Kramarenko, V. A. Matveev, V. A. Polyakov, V. D. Samoylenko, V. E. Lyubovitskij, V. N. Frolov, V. N. Kolosov, V. O. Tikhomirov, V. Yu. Volkov, Y. Kambar, Yu. M. Andreev","submitted_at":"2024-06-04T06:10:52Z","abstract_excerpt":"We present the first results from a proof-of-concept search for dark sectors via invisible decays of pseudoscalar $\\eta$ and $\\eta'$ mesons in the NA64h experiment at the CERN SPS. Our novel technique uses the charge-exchange reaction of 50 GeV $\\pi^-$ on nuclei of an active target as the source of neutral mesons. The $\\eta, \\eta' \\to invisible$ events would exhibit themselves via a striking signature - the complete disappearance of the incoming beam energy in the detector. No evidence for such events has been found with $2.9\\times10^{9}$ pions on target accumulated during one day of data taki"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2406.01990","kind":"arxiv","version":1},"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/2406.01990/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"}