The anti-neutrino coming from the nuclear reactor interacts with a proton of the
target, giving a positron and a neutron. The positron annihilates with an electron
of target and gives two simultaneous photons. The neutron slows down before being
eventually captured by a cadmium nucleus, that gives the emission of photons about
one 15 microseconds after those of the positron. All those photons are detected
and the 15 microseconds identify the "neutrino" interaction.