Sensitivity of a multi-photomultiplier optical module for KM3NeT

For the KM3NeT neutrino telescope an optical module with a number of small photomultiplier tubes (multi-PMT optical module) will be advantageous for various reasons, e.g. reduced background rate, a larger number of coincidence hits, and sensitivity to ultra-high energy neutrinos. The properties of such a design have been investigated by measurements and simulations. Several types of 3 in. PMT were exposed to LED light pulses with intensities down to the single-photon level. The simulation tool Sirène for a photo-sensor based neutrino telescope has been applied to allow a comparison with the ANTARES detector. All muon directions can be observed with an improved identification and rejection of atmospheric muons. For up-going neutrinos and down-going muons the multi-PMT arrangement shows a better performance in both the photo-electron response and in the number-of-hits response as compared to the present ANTARES design.