/ nucl-ex arXiv:1311.0168

The neutron skin of $^{208}$Pb from coherent pion photoproduction

Watts, D.P. (Edinburgh U.) ; Glazier, D.I. (Edinburgh U.) ; Aguar, P. (Mainz U., Inst. Kernphys.) ; Ahrens, J. (Mainz U., Inst. Kernphys.) ; Annand, J.R.M. (Glasgow U.) ; Arends, H.J. (Mainz U., Inst. Kernphys.) ; Beck, R. (Bonn U., HISKP) ; Bekrenev, V. (St. Petersburg, INP) ; Boillat, B. (Basel U.) ; Braghieri, A. (INFN, Pavia) ; Branford, D. (Edinburgh U.) ; Briscoe, W.J. (George Washington U.) ; Brudvik, J. (UCLA) ; Cherepnya, S. (Lebedev Inst.) ; Codling, R. (Glasgow U.) ; Downie, E.J. (Glasgow U.) ; Foehl, K. (Edinburgh U.) ; Grabmayr, P. (Tubingen U.) ; Gregor, R. (Giessen U.) ; Heid, E. (Mainz U., Inst. Kernphys.) ; Hornidge, D. (Mt. Allison U.) ; Jahn, O. (Mainz U., Inst. Kernphys.) ; Kashevarov, V.L. (Lebedev Inst.) ; Knezevic, A. (Boskovic Inst., Zagreb) ; Kondratiev, R. (Dubna, JINR) ; Korolija, M. (Boskovic Inst., Zagreb) ; Kotulla, M. (Basel U.) ; Krambrich, D. (Bonn U., HISKP) ; Krusche, B. (Basel U.) ; Lang, M. (Bonn U., HISKP) ; Lisin, V. (Dubna, JINR) ; Livingston, K. (Glasgow U.) ; Lugert, S. (Giessen U.) ; MacGregor, I.J.D. (Glasgow U.) ; Manley, D.M. (Kent State U.) ; Martinez, M. (Mainz U., Inst. Kernphys.) ; McGeorge, J.C. (Glasgow U.) ; Mekterovic, D. (Boskovic Inst., Zagreb) ; Metag, V. (Giessen U.) ; Nefkens, B.M.K. (UCLA) ; Nikolaev, A. (Bonn U., HISKP) ; Novotny, R. (Giessen U.) ; Owens, R.O. (Glasgow U.) ; Pedroni, P. (INFN, Pavia) ; Polonski, A. (Dubna, JINR) ; Prakhov, S.N. (UCLA) ; Price, J.W. (UCLA) ; Rosner, G. (Glasgow U.) ; Rost, M. (Mainz U., Inst. Kernphys.) ; Rostomyan, T. (INFN, Pavia) ; Schadmand, S. (Giessen U.) ; Schumann, S. (Bonn U., HISKP) ; Sober, D. (Catholic U.) ; Starostin, A. (UCLA) ; Supek, I. (Boskovic Inst., Zagreb) ; Thomas, A. (Mainz U., Inst. Kernphys.) ; Unverzagt, M. (Bonn U., HISKP) ; Walcher, Th. (Mainz U., Inst. Kernphys.) ; Zehr, F. (Basel U.)

Pages: 5

Abstract: Information on the size and shape of the neutron skin on $^{208}$Pb has been extracted from coherent pion photoproduction cross sections measured using the Crystal Ball together with the Glasgow tagger at the MAMI electron beam facility. Exploiting 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 6.77$\pm 0.03(stat)$ fm and 0.55$\pm 0.01(stat)$$^{+0.00}_{-0.025}(sys)$ fm respectively, corresponding to a neutron skin thickness $\Delta r_{np}$=0.19$\pm 0.03(stat)$$^{+0.00}_{-0.03}(sys)$ fm. The results give the first successful extraction of a neutron skin with an electromagnetic probe and indicate 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.

Web-Page: http://inspirehep.net/record/1263097/files/figure1.png; http://inspirehep.net/record/1263097/files/figure2.png; http://inspirehep.net/record/1263097/files/figure3.png; http://inspirehep.net/record/1263097/files/figure4.png; http://inspirehep.net/record/1263097/files/arXiv:1311.0168.pdf

Note: *Brief entry*; 4 figures 5 pages

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 Record created 2013-11-11, last modified 2014-01-30

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