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Decay at Rest

On the other hand, the disadvantage of the stopped pion technique is that one accepts into the detectors all the Michel positrons from muon decays in the target. In addition, one measures the branching ratio for pion beta decay. Then the decay rate is obtained from the measured branching ratio using the pion life time.

Clearly, the design of the apparatus, especially the size and the cost of the detectors, is affected by the decay method used. The design of the pion beta calorimeter stems from a decay at rest method which relies on the similarity between the and decays in terms of their systematic uncertainties. This enables a relative measurement of the pion beta decay rate without the absolute knowledge of acceptances and conversion efficiencies for both processes as required in the in-flight technique. Furthermore, the relative stopped pion technique finds its justification in the drawbacks to the in-flight technique, particularly the difficulty in controlling the systematic uncertainties with accuracy in an absolute measurement of the pion beta decay which occurs with a probability of .

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