next up previous contents
Next: Contents


Kétévi Adiklè Assamagan
Lomé Togo,
Afrique Occidentale

B.S., Université Du Bénin, 1985
M.S., Ball State University, 1989

A Dissertation Presented to the Graduate
Faculty of the University of Virginia
in Candidacy for the Degree of
Doctor of Philosophy

Department of Physics
University of Virginia

May 1995


A precise determination of the pion beta decay rate constitutes a stringent test for the Cabibbo universality through the Conserved Vector Current (CVC) hypothesis and for the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix. The unitarity of the CKM matrix can be used to constrain certain extensions to the minimal Standard Model (SM), for instance the existence of a fourth generation of quarks. The discrepancy between superallowed Fermi decay and neutron beta decay data, and the level of accuracy of the previous experiments on pion beta decay call for a new precision measurement of rate. This precision experiment is currently in progress at the Paul Scherrer Institute in Switzerland. The design of the experimental apparatus and its calibration are the subject of this work. Positive pions of momentum of 116 MeV/c were stopped in a scintillator fiber hodoscope. The beam distributions and contaminations have been investigated and measured. Monte Carlo simulations aided in the design of the apparatus, especially the shower calorimeter, and the response of its modules to monoenergetic positrons and photons have been measured. A cosmic ray tomography apparatus is being used to determine the light collection non-uniformity of each of the CsI modules. Finally, the response of the apparatus to events has been measured, since these events will be used for normalization purposes in determining the pion beta decay rate.

next up previous contents
Next: Contents

Bernward Krause
Mon Jan 15 14:57:06 MET 1996