Life time measurements of unstable charged particles of cosmic radiation using emulsions

Summary  In the present paper two different procedures are described which both allow the determination of the mean life of charged unstable particles whose tracks are observed in nuclear emulsions. The first procedure, which has been already presented in a preceding paper, is based on the method of «maximum likelihood». The second procedure is based on the use of the so called «residual time». This time is defined as follows: Let us consider a particle which decays in flight in the plate, with a velocityβ d at an instantt d . If it has not decayed it would have been brought to rest in the emulsion at a timet 0. The time intervalt d −t 0 is the «residual time» (see fig. 1). The combination of the two methods reduces the influence of experimental bias of both geometrical and kinematical origin. The application of these methods to the case of hyperons allows one to establish the following limits to their mean life: 3·10−10≥τ≥0.5·10−10 s.