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

TL;DR

This paper proposes a high-precision experimental setup to measure the branching ratio and lifetime of direct pion decay into positrons, aiming to test Standard Model predictions and search for new interactions.

Contribution

It introduces a novel detection setup using plastic scintillators and silicon photomultipliers to improve measurement accuracy of pion decay parameters by four times.

Findings

Measurement accuracy of branching ratio improved fourfold

First proposal to measure pion lifetime during direct decay with better than 7 ppm accuracy

Setup enables testing of Standard Model universality and new pseudoscalar interactions

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.