Measurement of CNGS Muon Neutrinos Speed with Borexino: INRIM and ROA Contribution

This paper describes the contribution given by the INRIM “Time and Frequency Laboratory” and the ROA “Time Department” to the Borexino cooperation in the experiments for the accurate measurement of the CNGS (CERN neutrinos to Gran Sasso) muon neutrinos speed. We briefly report about the design, installation, and performance of a new system called High Precision Timing Facility (HPTF), intended as a GPS-based timing facility with a calibrated time-link to the CERN GPS receiver and with continual real time monitoring of the fiber link time delay to the underground laboratory. Details about the INRIM/ROA contribution will be presented, reporting the calibration of the CERN-LNGS GPS time link, as well as the calibration of the HPTF internal delays. This system, specifically designed for the Borexino experiments, has also been made available to other LNGS experiments (namely, LVD and Icarus) and has been used to measure the muon neutrino speed in May 2012, during a special short bunch run of the CNGS beam.