Physics Letters B (Nov 2018)
First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons
- A. Käser,
- M. Dieterle,
- L. Witthauer,
- S. Abt,
- P. Achenbach,
- P. Adlarson,
- F. Afzal,
- Z. Ahmed,
- J. Ahrens,
- J.R.M. Annand,
- H.J. Arends,
- M. Bashkanov,
- R. Beck,
- M. Biroth,
- N.S. Borisov,
- A. Braghieri,
- W.J. Briscoe,
- F. Cividini,
- C. Collicott,
- S. Costanza,
- A. Denig,
- E.J. Downie,
- P. Drexler,
- A. Fix,
- S. Garni,
- D.I. Glazier,
- I. Gorodnov,
- W. Gradl,
- M. Günther,
- G.M. Gurevich,
- L. Heijkenskjöld,
- D. Hornidge,
- G.M. Huber,
- V.L. Kashevarov,
- S. Kay,
- I. Keshelashvili,
- R. Kondratiev,
- M. Korolija,
- B. Krusche,
- A.B. Lazarev,
- V. Lisin,
- K. Livingston,
- S. Lutterer,
- I.J.D. MacGregor,
- D.M. Manley,
- P.P. Martel,
- V. Metag,
- W. Meyer,
- R. Miskimen,
- E. Mornacchi,
- A. Mushkarenkov,
- A.B. Neganov,
- A. Neiser,
- M. Oberle,
- M. Ostrick,
- P.B. Otte,
- D. Paudyal,
- P. Pedroni,
- A. Polonski,
- S.N. Prakhov,
- G. Reicherz,
- G. Ron,
- T. Rostomyan,
- A. Sarty,
- C. Sfienti,
- V. Sokhoyan,
- K. Spieker,
- O. Steffen,
- I.I. Strakovsky,
- Th. Strub,
- I. Supek,
- A. Thiel,
- M. Thiel,
- A. Thomas,
- M. Unverzagt,
- Yu.A. Usov,
- S. Wagner,
- N.K. Walford,
- D.P. Watts,
- D. Werthmüller,
- J. Wettig,
- M. Wolfes,
- L. Zana
Affiliations
- A. Käser
- Department of Physics, University of Basel, Basel, Switzerland
- M. Dieterle
- Department of Physics, University of Basel, Basel, Switzerland
- L. Witthauer
- Department of Physics, University of Basel, Basel, Switzerland
- S. Abt
- Department of Physics, University of Basel, Basel, Switzerland
- P. Achenbach
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- P. Adlarson
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- F. Afzal
- Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Bonn, Germany
- Z. Ahmed
- University of Regina, Regina, SK S4S 0A2, Canada
- J. Ahrens
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- J.R.M. Annand
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
- H.J. Arends
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- M. Bashkanov
- SUPA School of Physics, University of Edinburgh, Edinburgh EEH9 3JZ, UK
- R. Beck
- Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Bonn, Germany
- M. Biroth
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- N.S. Borisov
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
- A. Braghieri
- INFN Sezione di Pavia, Pavia, Italy
- W.J. Briscoe
- Center for Nuclear Studies, The George Washington University, Washington, DC, USA
- F. Cividini
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- C. Collicott
- Department of Astronomy and Physics, Saint Marys University, Halifax, Canada
- S. Costanza
- INFN Sezione di Pavia, Pavia, Italy
- A. Denig
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- E.J. Downie
- Institut für Kernphysik, University of Mainz, Mainz, Germany; Center for Nuclear Studies, The George Washington University, Washington, DC, USA
- P. Drexler
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- A. Fix
- Laboratory of Mathematical Physics, Tomsk Polytechnic University, Tomsk, Russia
- S. Garni
- Department of Physics, University of Basel, Basel, Switzerland
- D.I. Glazier
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK; SUPA School of Physics, University of Edinburgh, Edinburgh EEH9 3JZ, UK
- I. Gorodnov
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
- W. Gradl
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- M. Günther
- Department of Physics, University of Basel, Basel, Switzerland
- G.M. Gurevich
- Institute for Nuclear Research, Moscow, Russia
- L. Heijkenskjöld
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- D. Hornidge
- Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada
- G.M. Huber
- University of Regina, Regina, SK S4S 0A2, Canada
- V.L. Kashevarov
- Institut für Kernphysik, University of Mainz, Mainz, Germany; Joint Institute for Nuclear Research, 141980 Dubna, Russia
- S. Kay
- SUPA School of Physics, University of Edinburgh, Edinburgh EEH9 3JZ, UK
- I. Keshelashvili
- Department of Physics, University of Basel, Basel, Switzerland
- R. Kondratiev
- Institute for Nuclear Research, Moscow, Russia
- M. Korolija
- Rudjer Boskovic Institute, Zagreb, Croatia
- B. Krusche
- Department of Physics, University of Basel, Basel, Switzerland; Corresponding author.
- A.B. Lazarev
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
- V. Lisin
- Institute for Nuclear Research, Moscow, Russia
- K. Livingston
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
- S. Lutterer
- Department of Physics, University of Basel, Basel, Switzerland
- I.J.D. MacGregor
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
- D.M. Manley
- Kent State University, Kent, OH, USA
- P.P. Martel
- Institut für Kernphysik, University of Mainz, Mainz, Germany; Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada
- V. Metag
- II. Physikalisches Institut, University of Giessen, Germany
- W. Meyer
- Institut für Experimentalphysik, Ruhr Universität, 44780 Bochum, Germany
- R. Miskimen
- University of Massachusetts Amherst, Amherst, MA 01003, USA
- E. Mornacchi
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- A. Mushkarenkov
- Institute for Nuclear Research, Moscow, Russia; University of Massachusetts Amherst, Amherst, MA 01003, USA
- A.B. Neganov
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
- A. Neiser
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- M. Oberle
- Department of Physics, University of Basel, Basel, Switzerland
- M. Ostrick
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- P.B. Otte
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- D. Paudyal
- University of Regina, Regina, SK S4S 0A2, Canada
- P. Pedroni
- INFN Sezione di Pavia, Pavia, Italy
- A. Polonski
- Institute for Nuclear Research, Moscow, Russia
- S.N. Prakhov
- Institut für Kernphysik, University of Mainz, Mainz, Germany; University of California at Los Angeles, Los Angeles, CA, USA
- G. Reicherz
- Institut für Experimentalphysik, Ruhr Universität, 44780 Bochum, Germany
- G. Ron
- Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel
- T. Rostomyan
- Department of Physics, University of Basel, Basel, Switzerland
- A. Sarty
- Department of Astronomy and Physics, Saint Marys University, Halifax, Canada
- C. Sfienti
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- V. Sokhoyan
- Institut für Kernphysik, University of Mainz, Mainz, Germany; Center for Nuclear Studies, The George Washington University, Washington, DC, USA
- K. Spieker
- Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Bonn, Germany
- O. Steffen
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- I.I. Strakovsky
- Center for Nuclear Studies, The George Washington University, Washington, DC, USA
- Th. Strub
- Department of Physics, University of Basel, Basel, Switzerland
- I. Supek
- Rudjer Boskovic Institute, Zagreb, Croatia
- A. Thiel
- Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Bonn, Germany
- M. Thiel
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- A. Thomas
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- M. Unverzagt
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- Yu.A. Usov
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
- S. Wagner
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- N.K. Walford
- Department of Physics, University of Basel, Basel, Switzerland
- D.P. Watts
- SUPA School of Physics, University of Edinburgh, Edinburgh EEH9 3JZ, UK
- D. Werthmüller
- Department of Physics, University of Basel, Basel, Switzerland; SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
- J. Wettig
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- M. Wolfes
- Institut für Kernphysik, University of Mainz, Mainz, Germany
- L. Zana
- SUPA School of Physics, University of Edinburgh, Edinburgh EEH9 3JZ, UK
- Journal volume & issue
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Vol. 786
pp. 305 – 312
Abstract
The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2n,p and A3/2n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.
