Status of the PIENU experiment

T Numao ,L Doria ,S H Kettell ,M Blecher ,D A Bryman ,Y Igarashi ,A Hussein ,A A Aguilar-Arevalo ,L Littenberg ,S Ito ,S Chen,P Gumplinger ,Dorothea Vom Bruch ,J R Comfort ,T Sullivan ,S Cuen-Rochin ,D Protopopescu ,A Sher ,M Aoki ,L L Kurchaninov ,D Britton ,R E Mischke ,C Malbrunot ,D V Vavilov

doi:10.1088/1742-6596/556/1/012002

Abstract

The branching ratio, Re/μ = Γ(π → eν + eνγ)/Γ(π → μν + μνγ), provides a sensitive test of muon-electron universality in weak interactions. The status of the PIENU experiment at TRIUMF, which aims to improve the precision of the Re/μ measurement by a factor of > 5, is presented.

Highlights

IntroductionThe positron calorimeter located on the beam axis consisted of two thin plastic scintillators and a 48-cm (dia.) × 48-cm (length) single-crystal NaI(T ) detector [9]
The branching ratio of pion decays, Re/μ = Γ(π → eν + eνγ)/Γ(π → μν + μνγ), which has been precisely calculated by the Standard Model (SM) RSM = (1.2352 ± 0.0001) × 10−4 [1, 2], has provided one of the best tests of electron-muon universality in weak interactions
The positron calorimeter located on the beam axis consisted of two thin plastic scintillators and a 48-cm × 48-cm single-crystal NaI(T ) detector [9]

Summary

Introduction

The positron calorimeter located on the beam axis consisted of two thin plastic scintillators and a 48-cm (dia.) × 48-cm (length) single-crystal NaI(T ) detector [9]. A coincidence of pion and positron signals with a time window of –300 ns to 540 ns with respect to the pion signal from the beam counters was the basis of the main trigger logic. This was prescaled by a factor of 16 to form an unbiased trigger. The calorimeter was rotated to inject the beam at various entrance angles up to 48◦ with respect to the beam axis

Analysis

Findings

Conclusions