Neutron Skin of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Pb</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>208</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>from Coherent Pion Photoproduction

C. M. Tarbert(University of Edinburgh), D. P. Watts(University of Edinburgh), D. I. Glazier(University of Edinburgh), P. Aguar(Johannes Gutenberg University Mainz), J. Ahrens(Johannes Gutenberg University Mainz), J. R. M. Annand(University of Glasgow), H. J. Arends(Johannes Gutenberg University Mainz), R. Beck(Johannes Gutenberg University Mainz), V. Bekrenev(Petersburg Nuclear Physics Institute), B. Boillat(University of Basel), A. Braghieri(Istituto Nazionale di Fisica Nucleare, Sezione di Pavia), D. Branford(University of Edinburgh), W. J. Briscoe(George Washington University), J. Brudvik(University of California, Los Angeles), S. Cherepnya(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), R. F. B. Codling(University of Glasgow), E. J. Downie(University of Glasgow), K. Foehl(University of Edinburgh), P. Grabmayr(University of Tübingen), R. Gregor(University of Giessen), E. Heid(Johannes Gutenberg University Mainz), D. Hornidge(Mount Allison University), Oliver Jahn(Johannes Gutenberg University Mainz), V. L. Kashevarov(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), Andrea Knežević(Rudjer Boskovic Institute), R. Kondratiev(Institute for Nuclear Research), M. Korolija(Rudjer Boskovic Institute), M. Kotulla(University of Basel), D. Krambrich(Johannes Gutenberg University Mainz), B. Krusche(University of Basel), Μ. Lang(Johannes Gutenberg University Mainz), V. Lisin(Institute for Nuclear Research), K. Livingston(University of Glasgow), S. Lugert(University of Giessen), I. J. D. MacGregor(University of Glasgow), D. M. Manley(Kent State University), M. Martı́nez(Johannes Gutenberg University Mainz), J. C. McGeorge(University of Glasgow), D. Mekterović(Rudjer Boskovic Institute), V. Metag(University of Giessen), B. M. K. Nefkens(University of California, Los Angeles), A. Nikolaev(Johannes Gutenberg University Mainz), R. Novotny(University of Giessen), R.O. Owens(University of Glasgow), P. Pedroni(Istituto Nazionale di Fisica Nucleare, Sezione di Pavia), A. Polonski(Institute for Nuclear Research), S. Prakhov(University of California, Los Angeles), J. W. Price(University of California, Los Angeles), G. Rosner(University of Glasgow), M. Rost(Johannes Gutenberg University Mainz), T. Rostomyan(Istituto Nazionale di Fisica Nucleare, Sezione di Pavia), S. Schadmand(University of Giessen), Sven Schumann(Johannes Gutenberg University Mainz), D. I. Sober(Catholic University of America), A. Starostin(University of California, Los Angeles), I. Supek(Rudjer Boskovic Institute), A. Thomas(Johannes Gutenberg University Mainz), M. Unverzagt(Johannes Gutenberg University Mainz), Th. Walcher(Johannes Gutenberg University Mainz), L. Zana(University of Edinburgh), F. Zehr(University of Basel)
Physical Review Letters
June 18, 2014
10.1103/physrevlett.112.242502
Cited by 229Open Access
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Abstract

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.) fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.) fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.

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