/ Experiment-Nucl

Insight into the Narrow Structure in η Photoproduction on the Neutron from Helicity-Dependent Cross Sections

Witthauer, L. (Basel U.) ; Dieterle, M. (Basel U.) ; Abt, S. (Basel U.) ; Achenbach, P. (Mainz U., Inst. Kernphys.) ; Afzal, F. (Bonn U., HISKP) ; Ahmed, Z. (Regina U.) ; Annand, J. R. M. (Glasgow U.) ; Arends, H. J. (Mainz U., Inst. Kernphys.) ; Bashkanov, M. (Edinburgh U.) ; Beck, R. (Bonn U., HISKP) ; Biroth, M. (Mainz U., Inst. Kernphys.) ; Borisov, N. S. (Dubna, JINR) ; Braghieri, A. (INFN, Pavia) ; Briscoe, W. J. (George Washington U.) ; Cividini, F. (Mainz U., Inst. Kernphys.) ; Costanza, S. (INFN, Pavia) ; Collicott, C. (St. Mary's U., Halifax) ; Denig, A. (Mainz U., Inst. Kernphys.) ; Downie, E. J. (George Washington U.) ; Drexler, P. (Mainz U., Inst. Kernphys.) ; Ferretti-Bondy, M. I. (Mainz U., Inst. Kernphys.) ; Gardner, S. (Glasgow U.) ; Garni, S. (Basel U.) ; Glazier, D. I. (Edinburgh U.) ; Glowa, D. (Edinburgh U.) ; Gradl, W. (Mainz U., Inst. Kernphys.) ; Günther, M. (Basel U.) ; Gurevich, G. M. (Moscow, INR) ; Hamilton, D. (Glasgow U.) ; Hornidge, D. (Mt. Allison U.) ; Huber, G. M. (Regina U.) ; Käser, A. (Basel U.) ; Kashevarov, V. L. (Mainz U., Inst. Kernphys.) ; Kay, S. (Edinburgh U.) ; Keshelashvili, I. (Basel U.) ; Kondratiev, R. (Moscow, INR) ; Korolija, M. (Boskovic Inst., Zagreb) ; Krusche, B. (Basel U.) ; Lazarev, A. B. (Dubna, JINR) ; Linturi, J. M. (Mainz U., Inst. Kernphys.) ; Lisin, V. (Moscow, INR) ; Livingston, K. (Glasgow U.) ; Lutterer, S. (Basel U.) ; MacGregor, I. J. D. (Glasgow U.) ; Mancell, J. (Glasgow U.) ; Manley, D. M. (Kent State U.) ; Martel, P. P. (Mainz U., Inst. Kernphys.) ; Metag, V. (Giessen U.) ; Meyer, W. (Ruhr U., Bochum (main)) ; Miskimen, R. (Massachusetts U., Amherst) ; Mornacchi, E. (Mainz U., Inst. Kernphys.) ; Mushkarenkov, A. (Massachusetts U., Amherst) ; Neganov, A. B. (Dubna, JINR) ; Neiser, A. (Mainz U., Inst. Kernphys.) ; Oberle, M. (Basel U.) ; Ostrick, M. (Mainz U., Inst. Kernphys.) ; Otte, P. B. (Mainz U., Inst. Kernphys.) ; Paudyal, D. (Regina U.) ; Pedroni, P. (INFN, Pavia) ; Polonski, A. (Moscow, INR) ; Prakhov, S. N. (UCLA) ; Rajabi, A. (Massachusetts U., Amherst) ; Reicherz, G. (Ruhr U., Bochum (main)) ; Ron, G. (Hebrew U.) ; Rostomyan, T. (Basel U.) ; Sarty, A. (St. Mary's U., Halifax) ; Sfienti, C. (Mainz U., Inst. Kernphys.) ; Sikora, M. H. (Edinburgh U.) ; Sokhoyan, V. (George Washington U.) ; Spieker, K. (Bonn U., HISKP) ; Steffen, O. (Mainz U., Inst. Kernphys.) ; Strakovski, I. I. (George Washington U.) ; Strub, Th. (Basel U.) ; Supek, I. (Boskovic Inst., Zagreb) ; Thiel, A. (Bonn U., HISKP) ; Thiel, M. (Mainz U., Inst. Kernphys.) ; Thomas, A. (Mainz U., Inst. Kernphys.) ; Unverzagt, M. (Mainz U., Inst. Kernphys.) ; Usov, Yu. A. (Dubna, JINR) ; Wagner, S. (Mainz U., Inst. Kernphys.) ; Walford, N. K. (Basel U.) ; Watts, D. P. (Edinburgh U.) ; Werthmüller, D. (Glasgow U.) ; Wettig, J. (Mainz U., Inst. Kernphys.) ; Wolfes, M. (Mainz U., Inst. Kernphys.) ; Zana, L. (Edinburgh U.)

Published in: Phys.Rev.Lett.
Year: 2016
Vol.: 117    Num./Issue: 13
Page No: 132502
Pages: 5
Year: 2016-09-22 published

Abstract: The double polarization observable E and the helicity dependent cross sections σ1/2 and σ3/2 were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π0. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ1/2 and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2- (S11) and N 1/2+ (P11). Furthermore, the extracted Legendre coefficients of the angular distributions for σ1/2 are in good agreement with recent reaction model predictions assuming a narrow resonance in the P11 wave as the origin of this structure.

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DOI: 10.1103/PhysRevLett.117.132502
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