Measurement of the π~0 Differential Cross-Section with CLAS and Outlook into 12 GeV Hall C

摘要

Photoproduction of the π~0 meson was studied using the CLAS detector at Thomas Jefferson National Accelerator Facility using tagged incident beam energies spanning the range E_γ = 1.1 GeV - 5.45 GeV. The measurement is performed on a liquid hydrogen target in the reaction γp → pe~+e~-(γ). The final state of the reaction is the sum of two subprocesses for π~0 decay, the Dalitz decay mode of π~0 → e~+e~-γ and conversion mode where one photon from π~0 → γγ decay is converted into a e~+e~- pair. This specific final state reaction avoided limitations caused by single prompt track triggering and allowed a kinematic range extension to the world data on π~0 photoproduction to a domain never systematically measured before. We report the measurement of the π~0 differential cross-sections (dσ)/(dΩ) and (dσ)/(dt). The angular distributions agree well with the SAID parametrization for incident beam energies below 3 GeV, while an interpretation of the data for incident beam energies greater than 3 GeV is currently being developed. Included in the report will be a discussion of the future wide angle, exclusive photoproduction of π~0 experiment that will be performed in Hall C.