The measurements employ a large bore superconducting solenoid magnet
(surplus from a Magnetic Resonance Imaging (MRI) company). Polarized
positively charged muons produced at TRIUMF are directed into the
magnetic field where they are stopped at the centre of a precision
detector package. The magnet and the detectors are shown in concept form at the top of the TWIST home page. Photos of the magnet, and a
"stack" of detectors - ready for insertation into the magnet - are
After an individual muon is stopped in the target, the tracking system is watched for several microseconds. If a muon decay event is observed, the positron from the decay spirals outward in the magnetic field. By observing the angle through which the positron is emitted and measuring the radius of curvature of the track in the magnetic field using precision tracking chambers, the angular and momentum distributions of decay events can be reconstructed. Sample decay spirals for one such decay are shown below.
By carefully controlling systematic uncertainties in the experiment, and by collecting data from a sample of 1,000,000,000 decay events, the decay distributions can be studied at an accuracy of parts in 10,000. This accuracy heightens our sensitivity to various effects, including the possible existence of right-handed interactions.
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