A Study of the Structure of the Pi Meson via the Radioactive Pion Decay

Bychkov, Maxim Aleksandrovich, Department of Physics, University of Virginia
Pocanic, Dinko, Department of Physics, University of Virginia
Frlez, Emil, Department of Physics, University of Virginia
Crabb, Don, Department of Physics
Norum, Blaine, Department of Physics, University of Virginia

Two of the most important parameters describing pi meson structure are F V and F A , the vector and axial vector form factors, respectively. Their values can be determined primarily by measuring the π + → e + νγ radiative pion decay. This study is based on the 20,182 radiative pion decay events collected at the Paul Scherrer meson factory using a large acceptance detector and a stopped pion beam. A detailed analysis of the dependence of the decay rate on kinematic parameters has resulted in the following best fit values: F V =0.0262(15), F V =0.0118(3) and a=0.241(93), where the parameter a describes the momentum dependence of the form factors. This is the first experimental determination of a ever. The reported values of F V and F A represent nearly sixand twofold improvements in accuracy over previously published results, respectively, and are in an excellent agreement with predictions of the Standard Model.

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PHD (Doctor of Philosophy)
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