{"paper":{"title":"New Precise Measurement of the Pion Weak Form Factors in the Pi+ -> e+ nu gamma Decay","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["hep-ph","nucl-ex"],"primary_cat":"hep-ex","authors_text":"A. M. Rozhdestvensky, A. S. Korenchenko, A. van der Schaaf, B. A. VanDevender, D. Mekterovi\\'c, D. Mzhavia, D. Po\\v{c}ani\\'c, E. Frle\\v{z}, E. P. Velicheva, H.-P. Wirtz, I. Supek, M. Bychkov, M. Korolija, N. A. Kuchinsky, N. P. Kravchuk, N. V. Khomutov, O. A. Rondon-Aramayo, P. Robmann, S. M. Korenchenko, S. Ritt, S. Scheu, T. Kozlowski, T. Sakhelashvili, U. Straumann, V. A. Baranov, V. A. Kalinnikov, V. P. Volnykh, W. Bertl, W. Li, Yu. M. Bystritsky, Y. Wang, Z. Tsamalaidze","submitted_at":"2008-04-11T16:19:49Z","abstract_excerpt":"We have measured the $\\pi^+\\to {\\rm e}^+\\nu\\gamma$ branching ratio over a wide region of phase space, based on a total of 65,460 events acquired using the PIBETA detector. Minimum-$\\chi^2$ fits to the measured $(E_{e^+},E_\\gamma)$ energy distributions result in the weak form factor value of $F_A=0.0119(1)$ with a fixed value of $F_V=0.0259$. An unconstrained fit yields $F_V=0.0258(17)$ and $F_A=0.0117(17)$. In addition, we have measured $a=0.10(6)$ for the dependence of $F_V$ on $q^2$, the ${\\rm e}^{+}\\nu$ pair invariant mass squared, parametrized as $F_V(q^2)=F_V(0)(1+a\\cdot q^2)$. The branch"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"0804.1815","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/0804.1815/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"}