Precision 12C(α,γ) Angular Distribution Measurements: First Significant Physics Result with a Time Projection Chamber Operating in Gamma Beams

Precision 12C(α,γ) Angular Distribution Measurements: First Significant Physics Result with a Time Projection Chamber Operating in Gamma Beams | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Precision 12 C(α,γ) Angular Distribution Measurements: First Significant Physics Result with a Time Projection Chamber Operating in Gamma Beams Kristian Haverson, Robin Smith, Moshe Gai, Deran Schweitzer, Sarah Stern, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7262256/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Jan, 2026 Read the published version in Communications Physics → Version 1 posted You are reading this latest preprint version Abstract The carbon oxygen ratio (C/O) at the end of stellar helium burning is a crucial nuclear input to stellar evolution theory. It is determined by the rate of oxygen formation in the fusion of helium with 12 C, denoted as 12 C(α,γ) 16 O. Knowledge of the C/O ratio with sufficient accuracy has eluded measurements over the past 51 years. We previously demonstrated the feasibility of a new method using gamma beams to measure the time-reverse photo-dissociation reaction, 16 O(γ,α) 12 C, inside a Time Projection Chamber detector. Here we report the first significant ``Physics Result'' obtained using our new method. We used an N 2 O gas target that, unlike our previous measurement, allowed us to eliminate 12 C, photo-dissociation events - a significant background that can lead to systematic errors. In this current, essentially background-free measurement, we obtained detailed complete angular distributions (0°-180°) with higher statistics. Cross sections were measured over the 1 - resonance in 16 O at E cm ≈2.4 MeV, where previous measurements of 12 C(α,γ) 16 O exhibit a disturbing disagreement of the measured E1-E2 mixing phase angle (φ 12 ) with an elementary prediction of quantum mechanics. The agreement presented in this work demonstrates the viability of our new method and provides a strong impetus for conducting measurements at lower energies. Physical sciences/Physics/Nuclear physics/Experimental nuclear physics Physical sciences/Physics/Nuclear physics/Nuclear astrophysics Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 06 Jan, 2026 Read the published version in Communications Physics → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7262256","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":496109047,"identity":"dfb5da0f-8933-4b65-abeb-d35aeef2284b","order_by":0,"name":"Kristian 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Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7262256/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7262256/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The carbon oxygen ratio (C/O) at the end of stellar helium burning is a crucial nuclear input to stellar evolution theory. It is determined by the rate of oxygen formation in the fusion of helium with \u003csup\u003e12\u003c/sup\u003eC, denoted as \u003csup\u003e12\u003c/sup\u003eC(α,γ)\u003csup\u003e16\u003c/sup\u003eO. Knowledge of the C/O ratio with sufficient accuracy has eluded measurements over the past 51 years. We previously demonstrated the feasibility of a new method using gamma beams to measure the time-reverse photo-dissociation reaction, \u003csup\u003e16\u003c/sup\u003eO(γ,α)\u003csup\u003e12\u003c/sup\u003eC, inside a Time Projection Chamber detector. Here we report the first significant ``Physics Result'' obtained using our new method. We used an N\u003csub\u003e2\u003c/sub\u003eO gas target that, unlike our previous measurement, allowed us to eliminate \u003csup\u003e12\u003c/sup\u003eC, photo-dissociation events - a significant background that can lead to systematic errors. In this current, essentially background-free measurement, we obtained detailed complete angular distributions (0°-180°) with higher statistics. Cross sections were measured over the 1\u003csup\u003e-\u003c/sup\u003e resonance in \u003csup\u003e16\u003c/sup\u003eO at E\u003csup\u003ecm\u003c/sup\u003e≈2.4 MeV, where previous measurements of \u003csup\u003e12\u003c/sup\u003eC(α,γ)\u003csup\u003e16\u003c/sup\u003eO exhibit a disturbing disagreement of the measured E1-E2 mixing phase angle (φ\u003csup\u003e12\u003c/sup\u003e) with an elementary prediction of quantum mechanics. The agreement presented in this work demonstrates the viability of our new method and provides a strong impetus for conducting measurements at lower energies.","manuscriptTitle":"Precision 12C(α,γ) Angular Distribution Measurements: First Significant Physics Result with a Time Projection Chamber Operating in Gamma Beams","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-08 13:06:12","doi":"10.21203/rs.3.rs-7262256/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-physics","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsphys","sideBox":"Learn more about [Communications Physics](http://www.nature.com/commsphys/)","snPcode":"","submissionUrl":"","title":"Communications Physics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"063746fb-406d-4502-a358-375ec42eb575","owner":[],"postedDate":"August 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":52691832,"name":"Physical sciences/Physics/Nuclear physics/Experimental nuclear physics"},{"id":52691833,"name":"Physical sciences/Physics/Nuclear physics/Nuclear astrophysics"}],"tags":[],"updatedAt":"2026-01-22T08:12:23+00:00","versionOfRecord":{"articleIdentity":"rs-7262256","link":"https://doi.org/10.1038/s42005-025-02458-7","journal":{"identity":"communications-physics","isVorOnly":false,"title":"Communications Physics"},"publishedOn":"2026-01-06 05:00:00","publishedOnDateReadable":"January 6th, 2026"},"versionCreatedAt":"2025-08-08 13:06:12","video":"","vorDoi":"10.1038/s42005-025-02458-7","vorDoiUrl":"https://doi.org/10.1038/s42005-025-02458-7","workflowStages":[]},"version":"v1","identity":"rs-7262256","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7262256","identity":"rs-7262256","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}