SuperNEMO tracker completion

The SuperNEMO experiment aims to understand the puzzling relationship between matter and antimatter. To do this, we will study one of the most puzzling particles: the neutrino. We know that there are neutrinos and antineutrinos - we have observed them behaving differently - but we don't know what the real underlying difference is between them. With most particles the electric charge would be the key - for example electrons having negative charge and anti-electrons (positrons) having positive charge. However the neutrino has no electric charge, so when we compare neutrinos with antineutrinos what we see are two otherwise-identical particles that cause different reactions when they interact with matter. The puzzle then is whether neutrinos and antineutrinos are truly different particles, or whether they are actually the same type of particle, which in different situations can behave like either a particle or an antiparticle - and if this was true it would revolutionise our understanding of the relationship between matter and antimatter. SuperNEMO can investigate this question by studying a process called double-beta decay, where a nucleus undergoes a radioactive decay in which two neutrons turn into two protons, releasing two antineutrinos and two electrons. The two antineutrinos are the key here: if neutrinos and antineutrinos are different particles, these antineutrinos will simply leave our detector. However, if neutrinos and antineutrinos are in fact the same particle, these two antineutrinos can occasionally choose to annihilate with each other before leaving the selenium nucleus, and this will give an extra burst of energy to the electrons. With SuperNEMO we are therefore searching for these electrons with an extra kick of energy that may reveal to us something new about our understanding of the universe.