This sturdy metal door separates the stifling, diesel-infused air of the road tunnel from the clean, controlled atmosphere of the Laboratoire Souterraine de Modane, Europe’s deepest underground laboratory which is home to a particle physics experiment called SuperNEMO. The SuperNEMO detector, around six metres long, four metres high and three metres wide, sits in a tightly controlled clean room to protect it from contamination by the minute amounts of natural radioactivity present in dirt and dust.
The neutrino is an outlier among particles – and when scientists see outliers, we can’t help but suspect there is some deeper meaning behind the inconsistency which could reveal profound truth about the laws of nature.
When the neutrinos interact with matter they produce negatively charged electrons, but when the antineutrinos interact with matter they produce positively charged positrons, the electron’s antiparticle.
Should that happen, the two electrons produced in the double-beta decay would get an extra kick of energy from the annihilation – and that is what SuperNEMO is looking for: a tiny kick of energy that would require us to rethink how matter and antimatter are related.
This brings us to one of the most profound questions of physics: why is there more matter than antimatter in the universe? You might think we already know the answer to that: the Big Bang produced all the matter.
Since this revised Standard Model has a mechanism to break the symmetry between matter and antimatter, these super-heavy neutrinos also have the ability to “Choose” to decay into matter over antimatter, providing the early universe with the extra matter we now see.
So if you are ever in the Savoy region of France, enjoying some aprés-ski after a day on the slopes, spare a thought for the SuperNEMO detector – and the particle physicists like me, deep below you, waiting patiently for that radioactive decay that just might explain how you got to be there.