{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4a584cc3221bf4d4c1f5b2fffb4d1e2ae056457614e2006a15601901906900ef","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["be76ede68a3c85b032fb07d9c72ee16d12f04b07e28ff0c7d35c0b0a431114c5","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"669fb6d3a08b8d08426f14735281d7e7c0e415e9a173108e71ffee11225835e1","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"hep.electroweak-anomalies.hvp-ee-tension","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Measurements of how often electron-positron collisions make two pions disagree between experiments, and with supercomputer calculations. This number feeds the muon magnet prediction.","posed_since":"2023","precise":"Identify the cause of the disagreement among $\\sigma(e+e- \\to \\pi+ \\pi-)$ measurements near the $\\rho$ peak (CMD-3 2023 versus KLOE, BaBar, SND) and between data-driven and lattice a_mu^HVP,LO (difference $\\sim 2\\ \\text{to}\\ 3\\%$ of HVP). An answer locates the systematic error, the radiative-correction issue, or a physical effect responsible.","problem_ref":"be76ede68a3c85b032fb07d9c72ee16d12f04b07e28ff0c7d35c0b0a431114c5","references":"","settled_by":"New $\\pi\\,\\pi$ measurements (BaBar reanalysis, Belle II, BESIII, KLOE reanalysis, CMD-3 crosscheck) together with lattice windows and $\\tau$-decay data with isospin-breaking corrections.","status_note":"Unresolved as of 2025; the 2025 White Paper did not use data-driven HVP for its central value.","title":"Why do e+e- to pi+ pi- cross-section measurements disagree?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"28066fe1e69dd99ee720b003f5045012fc6a60d11917803e6a85adcae3adc661","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"ca3af8cdc8bd5a9c734b5af35aa052cdc6087172070ef0bdfb733da67b458f46","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ozPA_4IYzUzwYXcpniOyQc5bKz65Rg6sv1hkbZeVrVTS5qxPnyV6anTappfwfv-ltwu7LfO8twO6osn7l1A6AQ"},"schema":"pubphys.envelope/1"},"record_hash":"28066fe1e69dd99ee720b003f5045012fc6a60d11917803e6a85adcae3adc661","leaf_index":3328}