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Experiment Overview

MuLan Detector

The goal of µLan is a measurement of the µ+ lifetime to 2 ps (or 10-6 ). The µLan experiment will use a chopped surface muon beam with a 1.0 muons fill period and a 20 muons measuring period. Approximately 10 muons will arrive per fill period and approximately 8 electrons are detected per measurement period. This yields 4 x 105 Michel electrons per second or 1 x 1012 Michel electrons in roughly thirty days of 100% - live running. The time spectrum of the decay electrons after the fill-period determines the muon lifetime.

The incoming muons are counted in two t0 counters and stopped in a sulfur target. The decay electrons are counted in a nearly 4pi scintillator array which comprises a double layer of 180-elements of scintillating tiles that are symmetrically arranged about the target center. The signals from the tiles are fed to 500 MHz, 8-bit resolution, waveform digitizers.

The major experimental difficulties are effects that distort the measured time spectrum of Michel electron events. Such effects include : (i) pulse pile-up in the scintillator tiles, (ii) time distortions due to µ-spin precession, (iii) efficiency variations during the measurement period, and (iv) beam-related and cosmic-ray backgrounds.

Seema Dhamija
Last modified: Sun Oct 12 2003