LiDO

LiDO (Liquid Scintillation Muon Decay Observer) is an experiment for measuring the mean lifetime of cosmic muons. It is permanently installed in the CosmicLab at DESY in Zeuthen.

The decay of a muon produces one electron or one positron and two neutrinos. With the exception of the neutrinos, all these particles are detectable in the LiDO and play a role in the measurement: Charged elementary particles, such as the muon, generate light in the scintillator that is registered by the PMT. When a muon decays in the detector, the resulting electron or positron generates another light signal a short time later. To determine the mean lifetime of muons, the time difference between the first light signal from the muon and the second signal from the electron or positron is measured. If the time difference is smaller than 20 microseconds, the event is assumed to be a muon decay and will be stored in the data. The frequency distribution of the time differences allows the determination of the average lifetime with the aid of the decay law.

Setup

As seen on the photo, LiDO consists of:

a light-proof steel container filled with
12 litres of liquid scintillator,
a photomultiplier "looking" into the scintillator,
the high voltage supply for the PMT,
the data acquisition (DAQ card) also used in the CosMO Experiment,
a notebook, running the analysis program muonic.

Data Structure

The data available via the web interface contains the variables: time of the decay, time full hour, air pressure, temperature, time difference (time(muon)-time(electron/positron)), number of decays per hour. For more detailed information about the variables see: Description of the Dataset.

Possible Student Exercises

Estimate the average muon lifetime for different data sets, compare the results with the published value.
Investigate the rate of muon decays depending on time, atmospheric pressure and temperature.
Compare the results with your own lifetime measurements with the CosMO or the Kamiokannen experiment.

Example Diagrams

At the internet platform Cosmic@Web some example diagrams will be shown if you use the Session-ID LiDO-Experiment.

Decay Time of Muons

This frequency chart (1D histogram) shows how often which muon decay time was measured.
Thereto, several ranges are defined and all values that lie within a range are counted. With Cosmic@Web a certain number of such ranges (or bins) can be chosen. Here the decay times are divided into bins of 0.5 µs each.
A fitfunction shows the mathematical description of the process.

But how to conclude the lifetime of the muon from this distribution? What are the physical laws behind this measurement?

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LiDO

LiDO

Setup

Data Structure

Possible Student Exercises

Example Diagrams

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