Date of Award

Winter 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Committee Director

Moskov Amaryan

Committee Member

Ian Balitsky

Committee Member

Alexander Godunov

Committee Member

Chester Grosch

Committee Member

Lawrence Weinstein

Abstract

Photoproduction of the π0 meson was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photon energies spanning the range Eγ = 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 π0 decay, the Dalitz decay mode of π0 → e +e–γ and conversion mode where one photon from π0 → γγ decay is converted into a e+e – pair. This specific final state reaction avoided limitations caused by single prompt track triggering, while the span of incident photon energies allowed for measurements of π0 photoproduction to a domain never systematically measured before.

We report the measurement of the π0 differential cross sections dσ/dΩ and dσ/dt. The angular distributions agree well with the SAID parametrization for incident beam energies below 3 GeV. As a result with this new data, the χ2/p.d.f. of the global fit in the SAID parametrization improved to 3.1 from 3.7. For incident beam energies greater than 3 GeV a comparison of a model based on Generalized Parton Distributions (GPD) with experimental data shows significant discrepancy, requiring further model developments to describe the data.

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DOI

10.25777/yxgj-3c96

ISBN

9781321558654

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