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

A2 Collaboration at MAMI

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33 Scopus citations

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.

Original languageAmerican English
Article number132502
JournalPhysical Review Letters
Volume117
Issue number13
DOIs
StatePublished - 22 Sep 2016

Bibliographical note

Publisher Copyright:
© 2016 American Physical Society.

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