{"paper":{"title":"Towards Measuring the CP-Violating Phase with Atmospheric Neutrinos","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"An up-down flux ratio of sub-GeV atmospheric neutrinos can measure the CP-violating phase with sensitivity that exceeds T2HK near 90° and 270°.","cross_cats":[],"primary_cat":"hep-ph","authors_text":"Ho Man Yim, John F. Beacom, Matthew J. Dolan, Nicole F. Bell, Stephan A. Meighen-Berger","submitted_at":"2026-05-16T00:07:50Z","abstract_excerpt":"We propose a new approach to measuring the CP-violating phase in neutrino mixing using atmospheric neutrinos, differing significantly from prior work. We develop an up-down flux ratio for sub-GeV atmospheric neutrinos that incorporates realistic detection effects and reduces systematic uncertainties. For the example of Hyper-Kamiokande -- the first experiment with sufficient atmospheric-neutrino statistics in this energy range -- our approach can surpass the sensitivity of the Tokai to Hyper-Kamiokande (T2HK) long-baseline experiment near $\\mathit{\\delta_\\mathrm{CP} = 90^\\circ}$ and $\\mathit{2"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"For the example of Hyper-Kamiokande, our approach can surpass the sensitivity of the Tokai to Hyper-Kamiokande (T2HK) long-baseline experiment near δ_CP = 90° and 270°.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"Realizing this potential will require additional, but realistic, work to reduce theoretical uncertainties. This premise enters in the final paragraph of the abstract and is load-bearing because the claimed sensitivity gain is stated to depend on successfully lowering those uncertainties without new systematics.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"A new up-down flux ratio for sub-GeV atmospheric neutrinos enables Hyper-Kamiokande to measure the CP-violating phase with sensitivity surpassing T2HK near delta_CP of 90 and 270 degrees.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"An up-down flux ratio of sub-GeV atmospheric neutrinos can measure the CP-violating phase with sensitivity that exceeds T2HK near 90° and 270°.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"92e4df85e6bd474fdfeff7258c6000a3b67c9fa5a2ca94d7c6c7ad607a7f1d4d"},"source":{"id":"2605.16721","kind":"arxiv","version":1},"verdict":{"id":"88b326cc-fed4-47a5-8f1d-af576e31c6c1","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-19T21:39:39.827472Z","strongest_claim":"For the example of Hyper-Kamiokande, our approach can surpass the sensitivity of the Tokai to Hyper-Kamiokande (T2HK) long-baseline experiment near δ_CP = 90° and 270°.","one_line_summary":"A new up-down flux ratio for sub-GeV atmospheric neutrinos enables Hyper-Kamiokande to measure the CP-violating phase with sensitivity surpassing T2HK near delta_CP of 90 and 270 degrees.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"Realizing this potential will require additional, but realistic, work to reduce theoretical uncertainties. 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