Photoproduction of π0 mesons off neutrons in the nucleon resonance region

M Dieterle; I Keshelashvili; J Ahrens; J R M Annand; H J Arends; K Bantawa; P A Bartolome; R Beck; V Bekrenev; A Braghieri; D Branford; W J Briscoe; J Brudvik; S Cherepnya; B Demissie; E J Downie; P Drexler; L V Fil'kov; A Fix; D I Glazier; D Hamilton; E Heid; D Hornidge; D Howdle; G M Huber; I Jaegle; O Jahn; T C Jude; A Käser; V L Kashevarov; R Kondratiev; M Korolija; S P Kruglov; B Krusche; A Kulbardis; V Lisin; K Livingston; I J D MacGregor; Y Maghrbi; J Mancell; D M Manley; Z Marinides; M Martinez; J C McGeorge; E McNicoll; D Mekterovic; V Metag; S Micanovic; D G Middleton; A Mushkarenkov; B M K Nefkens; A Nikolaev; R Novotny; M Oberle; M Ostrick; B Oussena; P Pedroni; F Pheron; A Polonski; S N Prakhov; J Robinson; G Rosner; T Rostomyan; S Schumann; M H Sikora; D Sober; A Starostin; I Supek; M Thiel; A Thomas; M Unverzagt; D P Watts; D Werthmüller; L Witthauer; Crystal Ball/TAPS experiment at MAMI, A2 Collaboration

doi:10.1103/PhysRevLett.112.142001

Photoproduction of π0 mesons off neutrons in the nucleon resonance region

Phys Rev Lett. 2014 Apr 11;112(14):142001. doi: 10.1103/PhysRevLett.112.142001. Epub 2014 Apr 8.

Authors

M Dieterle¹, I Keshelashvili¹, J Ahrens², J R M Annand³, H J Arends², K Bantawa⁴, P A Bartolome², R Beck⁵, V Bekrenev⁶, A Braghieri⁷, D Branford⁸, W J Briscoe⁹, J Brudvik¹⁰, S Cherepnya¹¹, B Demissie⁹, E J Downie¹², P Drexler¹³, L V Fil'kov¹¹, A Fix¹⁴, D I Glazier⁸, D Hamilton³, E Heid², D Hornidge¹⁵, D Howdle³, G M Huber¹⁶, I Jaegle¹, O Jahn², T C Jude⁸, A Käser¹, V L Kashevarov¹⁷, R Kondratiev¹⁸, M Korolija¹⁹, S P Kruglov⁶, B Krusche¹, A Kulbardis⁶, V Lisin¹⁸, K Livingston³, I J D MacGregor³, Y Maghrbi¹, J Mancell³, D M Manley⁴, Z Marinides⁹, M Martinez², J C McGeorge³, E McNicoll³, D Mekterovic¹⁹, V Metag¹³, S Micanovic¹⁹, D G Middleton¹⁵, A Mushkarenkov⁷, B M K Nefkens¹⁰, A Nikolaev⁵, R Novotny¹³, M Oberle¹, M Ostrick², B Oussena²⁰, P Pedroni⁷, F Pheron¹, A Polonski¹⁸, S N Prakhov¹⁰, J Robinson³, G Rosner³, T Rostomyan¹, S Schumann⁵, M H Sikora⁸, D Sober²¹, A Starostin¹⁰, I Supek¹⁹, M Thiel²², A Thomas², M Unverzagt⁵, D P Watts⁸, D Werthmüller¹, L Witthauer¹; Crystal Ball/TAPS experiment at MAMI, A2 Collaboration

Affiliations

¹ Department of Physics, University of Basel, Switzerland.
² Institut für Kernphysik, University of Mainz, Germany.
³ Department of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom.
⁴ Kent State University, Kent, Ohio, USA.
⁵ Institut für Kernphysik, University of Mainz, Germany and Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Germany.
⁶ Petersburg Nuclear Physics Institute, Gatchina, Russia.
⁷ INFN Sezione di Pavia, Pavia, Italy.
⁸ School of Physics, University of Edinburgh, Edinburgh, United Kingdom.
⁹ Center for Nuclear Studies, The George Washington University, Washington, DC, USA.
¹⁰ University of California at Los Angeles, Los Angeles, California, USA.
¹¹ Lebedev Physical Institute, Moscow, Russia.
¹² Institut für Kernphysik, University of Mainz, Germany and Department of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom and Center for Nuclear Studies, The George Washington University, Washington, DC, USA.
¹³ II. Physikalisches Institut, University of Giessen, Germany.
¹⁴ Laboratory of Mathematical Physics, Tomsk Polytechnic University, Tomsk, Russia.
¹⁵ Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada.
¹⁶ University of Regina, Regina, Saskatchewan S4S 0A2 Canada.
¹⁷ Institut für Kernphysik, University of Mainz, Germany and Lebedev Physical Institute, Moscow, Russia.
¹⁸ Institute for Nuclear Research, Moscow, Russia.
¹⁹ Rudjer Boskovic Institute, Zagreb, Croatia.
²⁰ Institut für Kernphysik, University of Mainz, Germany and Center for Nuclear Studies, The George Washington University, Washington, DC, USA.
²¹ The Catholic University of America, Washington, DC, USA.
²² Institut für Kernphysik, University of Mainz, Germany and II. Physikalisches Institut, University of Giessen, Germany.

PMID: 24765945
DOI: 10.1103/PhysRevLett.112.142001

Abstract

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.