Apparatus for a Search for T-violating Muon Polarization in Stopped-Kaon Decays

TL;DR

This paper describes a specialized detector at KEK designed to measure T-violating muon polarization in stopped-kaon decays, aiming to detect potential new physics beyond the Standard Model.

Contribution

It introduces a novel detector setup with minimized systematic errors for precise measurement of T-violation in kaon decays.

Findings

Detector achieved high acceptance and low systematic errors.

Method successfully reconstructed decay planes and measured muon polarization.

Results contribute to understanding CP violation and potential new physics.

Abstract

The detector built at KEK to search for T-violating transverse muon polarization in K+ --> pi0 mu+ nu (Kmu3) decay of stopped kaons is described. Sensitivity to the transverse polarization component is obtained from reconstruction of the decay plane by tracking the mu+ through a toroidal spectrometer and detecting the pi0 in a segmented CsI(Tl) photon calorimeter. The muon polarization was obtained from the decay positron asymmetry of muons stopped in a polarimeter. The detector included features which minimized systematic errors while maintaining high acceptance.