{"paper":{"title":"First measurement using elliptically polarized photons of the double-polarization observable $E$ for $\\gamma p \\to p \\pi^0$ and $\\gamma p \\to n \\pi^+$","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"nucl-ex","authors_text":"A2 Collaboration: F. Afzal, A. Braghieri, A. Denig, A. Lazarev, A. Neganov, A. Neiser, A. Powell, A. Thiel, A. Thomas, B. Krusche, C. Collicott, C. Mullen, C.S. Akondi, C. Sfienti, D. Ghosal, D. Gurevich, D. Hornidge, D.I. Glazier, D.M. Manley, D. Paudyal, D.P. Watts, D. Werthm\\\"uller, E.J. Downie, E. Mornacchi, F. Cividini, G.M. Huber, G. Reicherz, H.J. Arends, I. Gorodnov, I.I. Strakovsky, I.J.D. MacGregor, I. Supek, J.R.M. Annand, J. Wettig, K. Livingston, K. Spieker, L. Heijkenskj\\\"old, L. Witthauer, M. Bashkanov, M. Biroth, M. Dieterle, M. Korolija, M. Mocanu, M. Oberle, M. Ostrick, M. Thiel, M. Wolfes, N. Borisov, N.K. Walford, N. Zachariou, O. Steffen, P. Achenbach, P. Adlarson, P.B. Otte, P. Drexler, P. Hurck, P. Pedroni, P.P. Martel, R. Beck, R.G. Macrae, R. Miskimen, S. Abt, S. Costanza, S. Fegan, S. Gardner, S.J.D. Kay, S. Lutterer, S. Wagner, T. Rostomyan, T. Strub, V.L. Kashevarov, V. Sokhoyan, W. Gradl, W.J. Briscoe, Yu.A. Usov, Z. Ahmed","submitted_at":"2024-02-08T10:08:32Z","abstract_excerpt":"We report the measurement of the helicity asymmetry $E$ for the $p\\pi^0$ and $n\\pi^+$ final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g.~$G$) and circularly polarized photons (e.g.~$E$) and a longitudinally polarized target. The new data cover a photon energy range 270 - 1400 "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2402.05531","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/2402.05531/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"}