In searching through 10^19 collision events, how do you know you have found a new element? Because of the clear and unique decay sequence involving the offloading of alpha particles, nuclear parcels consisting of two protons and two neutrons. In this case, nuclei of element 118 decay to become element 116 (hereby itself discovered for the first time), and then element 114, and then element 112 by emitting detectable alphas. The 112 nucleus subsequently fissions into roughly equal-sized daughter particles.
Element 118 has been created in experiments conducted at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia by a collaboration of researchers from Russia's Joint Institute for Nuclear Research and the Lawrence Livermore National Laboratory in California. Element 118, the heaviest element yet found, was produced through collisions that fused together Californium and Calcium atoms. Although element 118 is too unstable to detect directly, the presence of daughter elements resulting from the decay of element 118 gave clues to its fleeting existence.