Deep sea tests of a prototype of the KM3NeT digital optical module

[EN] The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deepwaters of the Mediterranean Sea. This digital optical module has a novel design with a very large photocathode area segmented by the use of 31 three inch photomultiplier tubes. It has been integrated in the ANTARES detector for in-situ testing and validation. This paper reports on the first months of data taking and rate measurements. The analysis results highlight the capabilities of the new module design in terms of background suppression and signal recognition. The directionality of the optical module enables the recognition of multiple Cherenkov photons from the same 40K decay and the localisation of bioluminescent activity in the neighbourhood. The single unit can cleanly identify atmospheric muons and provide sensitivity to the muon arrival directions.The authors wish to thank the ANTARES collaboration for agreeing to the installation of the DOM in the detector and for the technical support given. The research leading to these results has received funding from the European Community Sixth Framework Programme under Contract 011937 and the Seventh Framework Programme under Grant Agreement 212525.Adrián Martínez, S.; Ageron, M.; Aharonian, F.; Aiello, S.; Albert, A.; Ameli, F.; Anassontzis, E.... (2014). Deep sea tests of a prototype of the KM3NeT digital optical module. European Physical Journal C: Particles and Fields. 74(3056):1-8. https://doi.org/10.1140/epjc/s10052-014-3056-318743056KM3NeT Technical Design Report. ISBN 978-90-6488-033-9. http://km3net.org/TDR/TDRKM3NeTM.G. Aartsen et al. (IceCube Collaboration), First observation of PeV-energy neutrinos with IceCube. Phys. Rev. Lett. 111, 021103 (2013)M.G. Aartsen et al. (IceCube Collaboration), Evidence for high-energy extraterrestrial neutrinos at the IceCube detector. Science 342, 947 (2013). doi: 10.1126/science.1242856F. Halzen, D. Hooper, High-energy neutrino astronomy: the cosmic ray connection. Rep. Prog. Phys. 65, 1025 (2002)W. Bednarek, TeV neutrinos from microquasars in compact massive binaries. Astrophys. J. 631, 466 (2005)F.W. Stecker, Are diffuse high energy neutrinos and $$\gamma $$ γ -rays from starburst galaxies observable? Astropart. Phys. 26, 398 (2007)F.W. Stecker, A note on high energy neutrinos from AGN cores. Phys. Rev. D 72, 107301 (2005)A. Kappes et al., Potential neutrino signals from Galactic $$\gamma $$ γ -ray sources. Astrophys. J. 656, 870 (2007)S. Adrián-Martínez et al. (ANTARES Collaboration), Search for cosmic neutrino point sources with four years of data from the ANTARES telescope. Astrophys. J. 760, 53 (2012)M. Ageron et al. (ANTARES Collaboration), ANTARES: the first undersea neutrino telescope. Nucl. Instrum. Methods A 656, 11 (2011)S. Adrián-Martínez et al. (KM3NeT Collaboration), Expansion cone for the 3-inch PMTs of the KM3NeT optical modules. JINST 8, T03006 (2013)P. Timmer et al., Very low power, high voltage base for a Photo Multiplier Tube for the KM3NeT deep sea neutrino telescope. JINST 5, C12049 (2010)A. Zwart et al. (On behalf of the KM3NeT collaboration), A TDC for the characterization of KM3NeT PMTs. Nucl. Instrum. Methods A 725, 170 (2013)S. Anvar et al., Design and implementation of a nanosecond time-stamping readout system-on-chip for photo-detectors. Nucl. Instrum. Methods A 735, 587 (2014)J. Hogenbirk et al., A photonic readout and data acquisition system for deep-sea neutrino telescopes. Nucl. Instrum. Methods A 626–627, S166 (2011)A. Belias, K. Manolopoulos, Readout and data acquisition for KM3NeT. AIP Conf. Proc. 1535, 260 (2013)P. Amram et al. (ANTARES collaboration), The ANTARES optical module. Nucl. Instrum. Methods A 484, 369 (2002)E.G. Anassontzis et al., Nucl. Instrum. Methods A 479, 439 (2002)S. Aiello et al., The optical modules of the phase-2 of the NEMO project. J. Instrum. 8, P07001 (2013)J.A. Aguilar et al. (ANTARES Collaboration), Time calibration of the ANTARES neutrino telescope. Astropart. Phys. 34, 539 (2011)B. Herold (KM3NeT Collaboration), Study of 40K-induced rates for a KM3NeT design option with multi-PMT optical modules. Nucl. Instrum. Methods A 626–627, S234 (2011)Y. Becherini et al., A parameterisation of single and multiple muons in the deep water or ice. Astropart. Phys. 25, 1 (2006