Dielectric material : a non-conductor of electric charge in which an applied field
                 causes a displacement of charge but not a flow of charge.
                                                                                             Oxford Dictionary of Physics

Neutrino: a type of lepton that exists in three flavours, one associated electrons,
                 one with muons and one with tau particles. Each type has its own
                 antiparticle, they are uncharged, posses extremely small mass and travel
                 close to the speed of light. In addition, they react weakly with other
                 matter through the weak nuclear force.
                                                                                                                           Oxford Dictionary of Physics

Photomultiplier tube: a sensitive type of light detector in which electrons from a
                 photocathode are accelerated to a dynodes where several electrons are
                 liberated by each original photoelectron. The entire process is repeated
                 several times to produce the required electrical current. The dynodes are
                 housed in a vacuum tube and have high voltages across them.
                                                                                                                           Oxford Dictionary of Physics

Solar Neutrino Problem (SNP): current models of the sun predict it to release a
                  certain flux of neutrinos, however experimental detection of these
                  neutrinos has found this flux to be too low for the known energy output
                  of the sun. More recent measurements have only found 60-70% of the
                  expected amount.

                  Form a more detailed explanation, and the possible solution of neutrino
                  oscillation see SNO.