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Extensive atmospheric showers observed in coincidence by an underwater neutrino telescope and a HELYCON (HEllenic LYceum Cosmic Observatories Network) floating scintillation array, offer an efficient calibration tool for the angular offset and the absolute position of a deep sea neutrino Cherenkov telescope. We report results of our studies concerning systematic effects and the calibration potential of the proposed techniques in various ν -telescope configurations and detector deployment depths.

One module of NESTOR, the Mediterranean deep-sea neutrino telescope, was deployed at a depth of 4000m, 14km off the Sapienza Island, off the South West coast of Greece. The deployment site provides excellent environmental characteristics. The deployed NESTOR module is constructed as a hexagonal star like latticed titanium star with 12 Optical Modules and an one-meter diameter titanium sphere which houses the electronics. Power and data were transferred through a 30km electro-optical cable to the shore laboratory. In this report we describe briefly the detector and the detector electronics and discuss the first physics data acquired and give the zenith angular distribution of the reconstructed muons.

NESTOR is a deep-sea neutrino telescope that is under construction in the Ionian Sea off the coast of Greece at a depth of about 4000 m. This paper briefly reviews the detector structure and deployment techniques before describing in detail the calibration and engineering run of a test detector carried out in 2003. The detector was operated for more than 1 month and data was continuously transmitted to shore via an electro-optical cable laid on the sea floor. The performance of the detector is discussed and analysis of the data obtained shows that the measured cosmic ray muon flux is in good agreement with previous measurements and with phenomenological cosmic ray models.

A module of the NESTOR underwater neutrino telescope was deployed at a depth of 3800 m in order to test the overall detector performance and particularly that of the data acquisition systems.A prolonged period of running under stable operating conditions made it possible to measure the cosmic ray muon flux, I 0 � cos a ðhÞ, as a function of the zenith angle h.Measured values of index a and the vertical intensity I0

The use of time over threshold techniques for the digitization of the output signals of photomultiplier tubes is under consideration by the KM3 NeT consortium. The technique consists of the recording of the times that the leading and trailing edge of the waveform crosses a certain voltage threshold. However, more information can be obtained by applying the same scheme at multiple threshold levels. We present the accuracy of a Multi-Time over Threshold technique in measuring the arrival time and the corresponding charge of signals produced by the optical elements of a large underwater neutrino telescope. We describe the operation and performance of the technique using simulated KM3 NeT photomultiplier pulses and report on the photomultiplier waveforms reconstruction accuracy. Finally, we describe an optimization of the technique capable of distinguishing different pulse shapes.

We report on a simulation study of the calibration potential offered by floating Extensive Air Shower (EAS) detector stations (HELYCON), operating in coincidence with the KM3NeT Mediterranean deep-sea neutrino telescope. We describe strategies in order to investigate for possible systematic errors in reconstructing the direction of energetic muons as well as to determine the absolute position of the underwater detector., 5 pages, 4 figures; NIMA, 2011, 626-627

Corrigendum to ‘‘Time over threshold electronics for an underwater neutrino telescope’’ [Nucl. Instr. and Meth. Phys. Res. A 602 (1) (2009) 129–132] G. Bourlis , A.G. Tsirigotis , S.E. Tzamarias , D. Loukas , I. Mixailakis , I. Papadakis b a Physics Laboratory, School of Science and Technology, Hellenic Open University, Greece b NCSR DEMOKRITOS, Institute of Nuclear Physics, Detector Instrumentation Laboratory, Greece