Helicity-dependent cross sections and double-polarization observable E in η photoproduction from quasifree protons and neutrons

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dc.contributor.author Witthauer, L.
dc.contributor.author Dieterle, M.
dc.contributor.author Abt, S.
dc.contributor.author Achenbach, P.
dc.contributor.author Afzal, F.
dc.date.accessioned 2018-02-08T09:38:52Z
dc.date.available 2018-02-08T09:38:52Z
dc.date.issued 2017-05-01
dc.identifier.citation Physical Review C, 95, 055201 en_US
dc.identifier.issn 2469-9985
dc.identifier.uri https://journals.aps.org/prc/pdf/10.1103/PhysRevC.95.055201
dc.identifier.uri http://repository.seku.ac.ke/handle/123456789/3838
dc.description DOI:https://doi.org/10.1103/PhysRevC.95.055201 en_US
dc.description.abstract Precise helicity-dependent cross sections and the double-polarization observable E were measured for η photoproduction from quasifree protons and neutrons bound in the deuteron. The η → 2γ and η → 3π0 → 6γ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of η photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin (σ1/2). It is absent for reactions with parallel spin orientation (σ3/2) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them with Legendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of P11 and S11 partial waves to explain the narrow structure. en_US
dc.language.iso en en_US
dc.publisher American Physical Society en_US
dc.title Helicity-dependent cross sections and double-polarization observable E in η photoproduction from quasifree protons and neutrons en_US
dc.type Article en_US


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