Measurement of the muon decay spectrum with the ICARUS liquid Argon TPC

TL;DR

This paper demonstrates the ICARUS liquid Argon TPC's capability to accurately measure muon decay spectra, calibrate energy measurements, and determine the Michel rho parameter with high precision.

Contribution

It presents the first detailed measurement of the muon decay spectrum and Michel rho parameter using the ICARUS T600 detector with high spatial resolution.

Findings

Michel rho parameter measured as 0.72 +/- 0.06(stat.) +/- 0.08(syst.)

Energy resolution for electrons below 50 MeV is 11%/sqrt(E) + 2%

Calibration factors enable precise calorimetric reconstruction

Abstract

Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the muon decay energy spectrum from a sample of stopping muon events acquired during the test run of the ICARUS T600 detector. This detector allows the spatial reconstruction of the events with fine granularity, hence, the precise measurement of the range and dE/dx of the muon with high sampling rate. This information is used to compute the calibration factors needed for the full calorimetric reconstruction of the events. The Michel rho parameter is then measured by comparison of the experimental and Monte Carlo simulated muon decay spectra, obtaining rho = 0.72 +/- 0.06(stat.) +/- 0.08(syst.). The energy resolution for electrons below ~50 MeV is finally extracted from the simulated sample, obtaining (Emeas-Emc)/Emc = 11%/sqrt(E[MeV]) + 2%.