A detailed Geant4 simulation originally created for ANTARES optical modules (OM) has been
improved to include the KM3NeT directional OM simulation. Optical modules are reproduced
following technical drawings. Standard low-energy physics processes are combined with response
of bialkali photocathodes. The simulation setup is easily reconfigurable for various OMs and
environments (air, water). In particular, this simulation software is used to study the feasibility of
supernova neutrino detection with KM3NeT.
Although KM3NeT detectors are mainly designed for high-energy neutrino detection, the MeV
neutrino signal from a supernova can be identified as a simultaneous increase of the counting rate
of the optical modules in the detector. The light is mainly emitted by MeV positrons produced
by neutrinos interacting with free protons in water, inverse beta decay. The noise from the optical
background due to K40 decays in sea water and bioluminescence can be significantly reduced
by using nanosecond coincidences between the nearby placed PMTs. This technique has been
tested with the ANTARES storeys consisting of three 10-inch PMTs and is optimized for the
KM3NeT telescope where the directional OMs containing 31 3-inch PMT provide very promising
expectations.