Absolute energy scale calibration of the MAGIC telescope using muon images

The absolute overall light collection efficiency of the MAGIC telescope can be calibrated using isolated muons hitting the reflector. The geometry and the energy of the muons are reconstructed from the measured ring images and compared with Monte Carlo predictions. The amount of Cherenkov light produced by muons can be modeled with small systematic uncertainties. Muon images are recorded during normal observation with a rate of about 2 Hz. A continuous calibration can therefore be performed with no need for dedicated calibration runs. In addition the width of the muon ring images can be used to monitor the spot size of the reflector during normal data taking