Time calibration with atmospheric muon tracks in the ANTARES neutrino telescope

The ANTARES experiment consists of an array of photomultipliers distributed along 12lines and located deep underwater in the Mediterranean Sea. It searches for astrophysicalneutrinos collecting the Cherenkov light induced by the charged particles, mainly muons, pro-duced in neutrino interactions around the detector. Since at energies of ?10 TeV the muonand the incident neutrino are almost collinear, it is possible to use the ANTARES detectoras a neutrino telescope and identify a source of neutrinos in the sky starting from a precisereconstruction of the muon trajectory. To get this result, the arrival times of the Cherenkovphotons must be accurately measured. A to perform time calibrations with the precision re-quired to have optimal performances of the instrument is described. The reconstructed tracksof the atmospheric muons in the ANTARES detector are used to determine the relative timeoffsets between photomultipliers. Currently, this method is used to obtain the time calibrationconstants for photomultipliers on different lines at a precision level of 0.5 ns. It has also beenvalidated for calibrating photomultipliers on the same line, using a system of LEDs and laserlight devices