tau -LEPTON DECAY IN AN ARBITRARY PLANE-WAVE ELECTROMAGNETIC FIELD.

This paper discuses the tau yields PI , nu // tau decay process in a field formed by the superposition of two fields: a crossed constant field and and electromagnetic planewave field. An expression is derived for the decay probability under the assumption of a nonzero tau -neutrino mass. The dependence of the decay probability on the lepton spin and on the external-field parameters is analyzed. The variation of the decay probability with the neutrino mass and lepton spin yields information which may be useful for ascertaining the neutrino mass.