Two views of LEGEND’s scintillation light detector fibre modules (above and below) with light-capturing fibres (green), part of the equipment needed to try to spot antineutrinos annihilating each other
Photographer Enrico Sacchetti captured these dazzling photographs of essential components of an experiment that might ultimately shed light on one of contemporary physics’ biggest riddles.
LEGEND is a multinational initiative aimed at explaining why the cosmos has so much more matter than antimatter. The first stage, known as LEGEND-200, will begin collecting data at the Gran Sasso National Laboratory in Italy this year using very sensitive germanium detectors for the next five years.
Antimatter is made up of antiparticles that have the same mass as “normal” particles but have the opposite characteristics, such as charge. LEGEND-200 is investigating the possibility that neutrinos, which are small, light, and uncharged subatomic particles that are itself a mystery, are their own antiparticles. To put it another way, neutrinos and antineutrinos might be one and the same, annihilating a similar particle.
LEGEND-200 is testing this theory by looking for evidence of neutrinoless double beta decay, an uncommon yet speculative phenomenon. When two neutrons spontaneously transform into two protons, two electrons and two antineutrinos are emitted.
Underside of the cryostat that will be filled with liquid argon and hold the fibre modules
In theory, a pair of antineutrinos released by a doubly decaying germanium nucleus will occasionally annihilate one other, leaving just the emission of electrons — confirmation of a selective antimatter destruction event. If this is confirmed, we would have witnessed for the first time a mechanism that favors matter over antimatter, perhaps explaining the universe’s matter-antimatter imbalance.