{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T10:01:36Z","timestamp":1775037696554,"version":"3.50.1"},"reference-count":48,"publisher":"American Association for the Advancement of Science (AAAS)","issue":"6118","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Science"],"published-print":{"date-parts":[[2013,1,25]]},"abstract":"<jats:title>Proton Still Too Small<\/jats:title>\n          <jats:p>\n            Despite a proton's tiny size, it is possible to measure its radius based on its charge or magnetization distributions. Traditional measurements of proton radius were based on the scattering between protons and electrons. Recently, a precision measurement of a line in the spectrum of muonium\u2014an atom consisting of a proton and a muon, instead of an electron\u2014revealed a radius inconsistent with that deduced from scattering studies.\n            <jats:bold>\n              Antognini\n              <jats:italic>et al.<\/jats:italic>\n            <\/jats:bold>\n            (p.\n            <jats:related-article xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"doi\" issue=\"6118\" page=\"417\" related-article-type=\"in-this-issue\" vol=\"339\" xlink:href=\"10.1126\/science.1230016\">417<\/jats:related-article>\n            ; see the Perspective by\n            <jats:bold>\n              <jats:related-article xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"doi\" issue=\"6118\" page=\"405\" related-article-type=\"in-this-issue\" vol=\"339\" xlink:href=\"10.1126\/science.1233202\">Margolis<\/jats:related-article>\n            <\/jats:bold>\n            ) examined a different spectral line of muonium, with results less dependent on theoretical analyses, yet still inconsistent with the scattering result; in fact, the discrepancy increased.\n          <\/jats:p>","DOI":"10.1126\/science.1230016","type":"journal-article","created":{"date-parts":[[2013,1,24]],"date-time":"2013-01-24T20:49:59Z","timestamp":1359060599000},"page":"417-420","source":"Crossref","is-referenced-by-count":738,"title":["Proton Structure from the Measurement of 2S-2P Transition Frequencies of Muonic Hydrogen"],"prefix":"10.1126","volume":"339","author":[{"given":"Aldo","family":"Antognini","sequence":"first","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Quantenoptik, 85748 Garching, Germany."},{"name":"Institute for Particle Physics, Eidgen\u00f6ssische Technische Hochschule (ETH) Z\u00fcrich, 8093 Z\u00fcrich, Switzerland."}]},{"given":"Fran\u00e7ois","family":"Nez","sequence":"additional","affiliation":[{"name":"Laboratoire Kastler Brossel, \u00c9cole Normale Sup\u00e9rieure, CNRS and Universit\u00e9 Pierre et Marie Curie (UPMC), 75252 Paris, CEDEX 05, France."}]},{"given":"Karsten","family":"Schuhmann","sequence":"additional","affiliation":[{"name":"Institute for Particle Physics, Eidgen\u00f6ssische Technische Hochschule (ETH) Z\u00fcrich, 8093 Z\u00fcrich, Switzerland."},{"name":"Dausinger and Giesen GmbH, Roteb\u00fchlstra\u00dfe 87, 70178 Stuttgart, Germany."}]},{"given":"Fernando D.","family":"Amaro","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Universidade de Coimbra, 3004-516 Coimbra, Portugal."}]},{"given":"Fran\u00e7ois","family":"Biraben","sequence":"additional","affiliation":[{"name":"Laboratoire Kastler Brossel, \u00c9cole Normale Sup\u00e9rieure, CNRS and Universit\u00e9 Pierre et Marie Curie (UPMC), 75252 Paris, CEDEX 05, France."}]},{"given":"Jo\u00e3o M. R.","family":"Cardoso","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Universidade de Coimbra, 3004-516 Coimbra, Portugal."}]},{"given":"Daniel S.","family":"Covita","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Universidade de Coimbra, 3004-516 Coimbra, Portugal."},{"name":"I3N, Departamento de F\u00edsica, Universidade de Aveiro, 3810-193 Aveiro, Portugal."}]},{"given":"Andreas","family":"Dax","sequence":"additional","affiliation":[{"name":"Physics Department, Yale University, New Haven, CT 06520\u20138121, USA."}]},{"given":"Satish","family":"Dhawan","sequence":"additional","affiliation":[{"name":"Physics Department, Yale University, New Haven, CT 06520\u20138121, USA."}]},{"given":"Marc","family":"Diepold","sequence":"additional","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Quantenoptik, 85748 Garching, Germany."}]},{"given":"Luis M. 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