Under a mountain in Savoie, the hunt for “dark matter” particles, this parallel world which structures the Universe

Physicists have some strange ideas. They claim to have opened a new window on the Universe... under the Alps. Not the most practical way to see anything. And yet.
Near Modane (Savoie), in the middle of the Fréjus tunnel, 6 kilometers from the entrance, between France and Italy, a metal gate, gray with tar and plastic, is marked with a no-entry sign. One of the physicists in a yellow vest gives the go-ahead to cross the dual carriageway on foot after the passage of heavy goods vehicles and cars. Behind the first gate, a second, then a third. Finally, a vast gallery opens up that plunges into the mountain, almost vertically to the tip of Fréjus, which culminates 1,700 meters higher, at 2,932 meters.
On the right, a room a few square meters in size, with transparent walls that appear fragile. Inside, the prototype of an observation "window" that is almost unique in the world, called "Damic-M". "We nickname it "The Beautiful Room", LBC, for "Low Background Chamber" [low noise chamber] " , describes Antoine Letessier-Selvon, CNRS researcher at the Laboratory of Nuclear Physics and High Energy (CNRS/Sorbonne University), the scientific coordinator of this mainly American-French experiment, which involves around fifty people.
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Le Monde