Darmstadt 2016 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 47: Hadron Structure and Spectroscopy VIII

HK 47.2: Talk

Thursday, March 17, 2016, 14:30–14:45, S1/01 A5

Study of excited η mesons at CLAS. — •Cathrina Sowa — Institut für Experimentalphysik I, Ruhr Universität Bochum

The analysis presented in this talk focuses on the reaction
γ p → p π⁺ π⁻ η to investigate excitations of η mesons. The CLAS experiment at CEBAF at Jefferson Laboratory investigates photoproduction on the proton with high intensities. The observed η′ as well as the η(1295) and η(1405) decay preferably to π⁺ π⁻ η.

Based on SU(3) symmetry for the light mesons a singlet as well as an octet is formed. Each contains one isoscalar state which mix to the lightest pseudoscalar mesons η and η′. Thus two first radial excitations are expected, but three states were found: η(1295), η(1405) and η(1475). The η(1405) is debated to be a gluonic bound state because it has been observed in gluon rich production mechanisms only. In this scenario the η(1405) should have a low production cross section in γ γ fusion or photoproduction.

We report on preliminary results for η′,f₁(1285)/η(1295) and η(1405) production cross sections in γ p → p π⁺ π⁻ η.