[Clas_hadron] [EXTERNAL] Abstract for SESAPS Meeting

[Volker Crede]

Dear Colleagues,

Please find below an abstract prepared by my graduate student Tianqi Hu for a contributed talk at the SESAPS (SouthEastern Section of the APS) meeting in Tallahassee, November 18-20.

Best wishes,

       Volker


Measurements of η and ω photoproduction beyond the nucleon resonance regime

Measurements of light-meson photoproduction are critical for understanding the underlying production mechanism in photon-nucleon interaction. At low energies, nucleon resonances have been extensively studied using techniques such as partial wave analysis. However, scarcities of cross section and polarization data over the photon energy range 3-6 GeV have thus far hindered our understanding of the transition from the nucleon resonance regime to a description of the reaction mechanism in terms of t-channel Pomeron and Regge exchanges. In this talk, we will present recent measurements of η and ω meson differential cross sections, and ω meson spin density matrix elements (SDMEs) from close to the production thresholds up to about 5 GeV using the data collected at Jefferson Lab during the CLAS-g12 run period. The circularly polarized ω SDMEs have been measured for the first time. The production mechanism will be discussed in comparison with various models. The η and ω differential cross sections have been fairly well described by the η-MAID 2018 and Laget models, respectively. The observed flip-sign discrepancy of the ω SDME ρ01−1 with the JPAC model implies that the potential contribution of the unnatural-parity t-channel exchanges to the ω photoproduction is smaller than the model predicted.

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