Results from the ICARUS T 600 module A measurement of the μ decay spectrum

We have studied the μ decay energy spectrum from a sample of stopping μ events acquired during the test run of the ICARUS T600 prototype. This detector allows the spatial reconstruction of the events with fine granularity, hence the precise measurement of the μ range and dE/dx with high sampling rate. This information is used to compute the correction factors needed for the calorimetric reconstruction. The Michel ρ parameter is then measured by comparison of the experimental and Monte Carlo simulated μ decay spectra, obtaining ρ = 0.72 ± 0.06 (stat.)± 0.08 (syst.). PACS. 13.15.+g Neutrino interactions – 13.35.Bv Decays of muons