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Measurements of $\eta$ and $\omega$ Photoproduction Beyond The Nucleon Resonance Regime

ORAL

Abstract

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 t-channel Pomeron and Regge exchanges. In this talk, we will present recent measurements of $\eta$ and $\omega$ meson differential cross sections, and $\omega$ meson spin density matrix elements(SDMEs) from close to the production thresholds up to the t-channel regime using the data collected at Jefferson Lab during the CLAS g12 run period. The circularly-polarized $\omega$ SDMEs have been measured for the first time. The production mechanism will be discussed in comparison with various models. The $\eta$ and $\omega$ differential cross sections have been fairly well described by the $\eta$-MAID 2018 and Laget models, respectively. The flip-sign discrepancy of the $\omega$ SDME $\rho^{0}_{1-1}$ with the JPAC model implies the potential contribution of unnatural-parity exchanges is smaller than the previous model predicted.

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Authors

  • Tianqi Hu

    Florida State University

  • Robert Grzywacz

    Moscow Institute of Physics and Technology, University of Virginia, California Institute of Technology, National High Magnetic Field Laboratory, University and Student Affairs; Oak Ridge Laboratory, Brookhaven National Laboratory, Physicist, Brookhaven National Laboratory, Oak Ridge National Laboratory, USA, Center for Nuclear Study, University of Tokyo, Advanced Science Research Center, Japan Atomic Energy Agency, Florida State University, Presidency University, Kolkata, INDIA, VECC,Kolkata, INDIA, SINP,Kolkata, INDIA, UGC-DAE CSR (Kolkata), INDIA, IFIN-HH, ELI-NP, Romania, Variable Energy Cyclotron Centre,Kolkata, INDIA, IEM, Kolkata, India, Victoria Institution (College), Kolkata, INDIA, Variable Energy Cyclotron Centre, Kolkata, INDIA, NHMFL; Florida State University, FAMU-FSU College of Engineering, Florida State University, Physics Department, Florida State University, Mississippi State University, NHMFL-FSU, U. Colorado at Boulder, NHMFL, University of Alabama at Birmingham, Oak Ridge National Laboratory, Argonne National Laboratory, Alabama School of Math and Science, University of South Alabama, University of Florida, University of Notre Dame, University of Texas at Dallas, Bob Jones University, University of Tennessee at Chattanooga, The Autonomous University of San Luis Potosí, Northern Arizona University, Flagstaff, AZ, Harvard-Smithsonian Center for Astrophysics, Cambridge, National Institute of Standards and Technology, Clemson University, University of South Florida, Phenikaa University, University of Ulsan, Ohio University, University of Hawaii, University of California, Davis, University of California, Davis., Saleh Research Centre, Department of Physics, Florida State university, Tallahassee, FL32306, USA, WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK, Professor, facility manager, Student, Florida State University(Former), Hebrew University, Israel \& Ioffe Institute, St.\ Petersburg, Russia, University of Tennessee, Knoxville

  • Volker Crede

    Florida State University, CLAS Collaboration, Florida State University