LiDO (Liquid Scintillation Muon Decay Observer) is an experiment installed in the CosmicLab at DESY in Zeuthen. The goal is to continuously measure the decay of muons into an electron or a positron and 2 neutrinos. The muon generates a short light flash in the liquid scintillator. This flash is followed by a second signal from the electron or positron. The neutrinos are not detectable. The two light flashes are detected by the PMT. If the time difference is smaller than 20 microseconds, the event is assumed to be a muon decay and will be stored on the notebook. The frequency distribution of the time difference allows us to estimate the average muon lifetime.


        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