Narrow structure in the excitation function of η photoproduction off the neutron.
The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5)  MeV and Γ=(30±15)  MeV. For the first time precise results for the angular dependence of this structure have been extracted.
Departement für Physik, Universität Basel, Switzerland.
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Werthmüller
Departement für Physik, Universität Basel, Switzerland.
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Witthauer
Departement für Physik, Universität Basel, Switzerland.
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Keshelashvili
Institut für Kernphysik, Universität Mainz, Germany.
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Aguar-Bartolomé
Institut für Kernphysik, Universität Mainz, Germany.
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Ahrens
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Annand
Institut für Kernphysik, Universität Mainz, Germany.
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Arends
Kent State University, Kent, Ohio, USA.
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Bantawa
Institut für Kernphysik, Universität Mainz, Germany and Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Germany.
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Beck
Petersburg Nuclear Physics Institute, Gatchina, Russia.
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Bekrenev
INFN Sezione di Pavia, Pavia, Italy.
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Braghieri
SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
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Branford
Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA.
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Briscoe
University of California at Los Angeles, Los Angeles, California, USA.
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Brudvik
Lebedev Physical Institute, Moscow, Russia.
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Cherepnya
Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA.
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Demissie
Departement für Physik, Universität Basel, Switzerland.
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Dieterle
Institut für Kernphysik, Universität Mainz, Germany and SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom and Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA.
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EJ
Downie
II. Physikalisches Institut, Universität Giessen, Germany.
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Drexler
Lebedev Physical Institute, Moscow, Russia.
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Fil'kov
Laboratory of Mathematical Physics, Tomsk Polytechnic University, Tomsk, Russia.
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Fix
SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
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Glazier
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Hamilton
Institut für Kernphysik, Universität Mainz, Germany.
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Heid
Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada.
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Hornidge
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Howdle
University of Regina, Regina, SK S4S 0A2, Canada.
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Huber
Departement für Physik, Universität Basel, Switzerland.
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Jaegle
Institut für Kernphysik, Universität Mainz, Germany.
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Jahn
SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
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Jude
Departement für Physik, Universität Basel, Switzerland.
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Käser
Institut für Kernphysik, Universität Mainz, Germany and Lebedev Physical Institute, Moscow, Russia.
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Kashevarov
Institute for Nuclear Research, Moscow, Russia.
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Kondratiev
Rudjer Boskovic Institute, Zagreb, Croatia.
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Korolija
Petersburg Nuclear Physics Institute, Gatchina, Russia.
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Kruglov
Departement für Physik, Universität Basel, Switzerland.
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Krusche
Petersburg Nuclear Physics Institute, Gatchina, Russia.
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Kulbardis
Institute for Nuclear Research, Moscow, Russia.
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Lisin
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Livingston
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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MacGregor
Departement für Physik, Universität Basel, Switzerland.
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Maghrbi
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Mancell
Kent State University, Kent, Ohio, USA.
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Manley
Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA.
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Marinides
Institut für Kernphysik, Universität Mainz, Germany.
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Martinez
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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McGeorge
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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McNicoll
II. Physikalisches Institut, Universität Giessen, Germany.
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Metag
Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada.
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Middleton
INFN Sezione di Pavia, Pavia, Italy.
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Mushkarenkov
University of California at Los Angeles, Los Angeles, California, USA.
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Nefkens
Institut für Kernphysik, Universität Mainz, Germany and Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Germany.
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Nikolaev
II. Physikalisches Institut, Universität Giessen, Germany.
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Novotny
Departement für Physik, Universität Basel, Switzerland.
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Oberle
Institut für Kernphysik, Universität Mainz, Germany.
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Ostrick
Institut für Kernphysik, Universität Mainz, Germany and Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA.
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Oussena
INFN Sezione di Pavia, Pavia, Italy.
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Pedroni
Departement für Physik, Universität Basel, Switzerland.
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Pheron
Institute for Nuclear Research, Moscow, Russia.
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Polonski
Institut für Kernphysik, Universität Mainz, Germany and Institute for Nuclear Studies, The George Washington University, Washington, District of Columbia, USA and University of California at Los Angeles, Los Angeles, California, USA.
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Prakhov
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Robinson
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Rosner
Departement für Physik, Universität Basel, Switzerland.
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Rostomyan
Institut für Kernphysik, Universität Mainz, Germany and Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Germany.
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Schumann
SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
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Sikora
The Catholic University of America, Washington, District of Columbia, USA.
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Sober
University of California at Los Angeles, Los Angeles, California, USA.
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Starostin
Rudjer Boskovic Institute, Zagreb, Croatia.
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Supek
Institut für Kernphysik, Universität Mainz, Germany and II. Physikalisches Institut, Universität Giessen, Germany.
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Thiel
Institut für Kernphysik, Universität Mainz, Germany.
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Thomas
Institut für Kernphysik, Universität Mainz, Germany and Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Germany.
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Unverzagt
SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
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Watts