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A precise measurement of the pion beta decay rate will allow accurate testing of the unitarity of the Cabbibo-Kobayashi-Maskawa quark mixing matrix, and of the Conserved Vector Current Hypothesis. The PIBETA collaboration intends to measure this decay rate with an accuracy of better than 0.5%, using a calorimeter comprised of 240 pure CsI crystals. Extensive calibrations of the CsI crystals have been done using cosmic muons. Further studies of the calorimeter response have been made using monoenergetic 70 MeV beam positrons, and using the box spectrum of photons ranging in energy from 55-83 MeV from the single charge exchange reaction tex2html_wrap_inline4804. Finally, a measurement of the Panofsky Ratio, defined as the ratio of the rate of single charge exchange to that of radiative pion capture tex2html_wrap_inline4806 in pionic hydrogen, has been made.

Penny Slocum
Fri Apr 2 00:36:38 EST 1999