By Gege Li
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
THESE gleaming images, taken by photographer Enrico Sacchetti, show key components of an experiment that could finally shed light on one of the biggest mysteries in modern physics.
LEGEND is an international project that aims to explain why there is so much more matter than antimatter in the universe. Starting this year, its first stage, called LEGEND-200, will use highly sensitive germanium detectors to collect data for the next five years at the Gran Sasso National Laboratory in Italy.
Antimatter is composed of antiparticles that have the same mass as “standard” particles, but with other properties, like charge, opposite to them. LEGEND-200 is examining the hypothesis that minuscule, light and uncharged subatomic particles called neutrinos – themselves a bit of a mystery – are their own antiparticles. In other words, neutrinos and antineutrinos may be one and the same, and could therefore annihilate a like particle.
The assembly of one fibre module
LEGEND-200 is probing this possibility by searching for evidence of a rare, theoretical process called neutrinoless double beta decay. This is when two neutrons spontaneously change into two protons, emitting two electrons and two antineutrinos.
Underside of the cryostat that will be filled with liquid argon and hold the fibre modules
A pair of antineutrinos emitted by a doubly decaying germanium nucleus will, in theory, sometimes annihilate each other, leaving only the emission of electrons – proof of an event that selectively destroys antimatter. If this is observed, we will have seen for the first time a process that favours the existence of matter over antimatter, possibly explaining the matter-antimatter imbalance in the universe.
More on these topics:neutrinos photography