Proposal to measure with high precision branching ratio of direct pion decay into positron and pion mean life

Abstract

Experimental measurement of the probability of direct decay of a pion into a positron allows searching for interactions beyond the Standard Model: test of the hypothesis about the universality of the charged current,search for new Pseudo-scalar Interactions. A setup based on plastic scintillators and silicon photomultipliers for measuring pion and muon energy losses without measuring the decay positron energy is proposed and analysed. It is shown that the accuracy of measuring the branching ratio of direct pion decay into positron can be improved fourfold. The pion lifetime measured only for decay a pion into a muon.For the first time, a project proposed to measure the lifetime of a pion during direct decay pion into positron with an accuracy of better than 7 ppm.