It is one of the greatest mysteries of modern physics: what does dark matter really consist of, that invisible entity that makes up 85% of all matter in the universe? The main candidates are WIMPs (Weakly Interacting Massive Particles), but they remain mere conjecture, predicted by the theory of supersymmetry. So far, scientists have only inferred the existence of dark matter indirectly, through its gravitational effects.
Hence the great anticipation aroused by the inauguration of the XENON1T detector, located deep in the Italian mountain Gran Sasso, about 150 kilometers from Rome. It is the largest WIMP hunter ever built: its 3.5 tons of liquid xenon will multiply almost ten times the sensitivity of the LUX laboratory in South Dakota, the largest dark matter detector to date.
Those responsible for XENON1T hope that it will join the Large Hadron Collider (LHC) experiments – also hunting for WIMPs – starting in March 2016. The stakes are very high: if neither of them will catch the long-awaited massive particles weak interaction, perhaps the time would have come to clean the slate and discard the theory of supersymmetry, the preferred one of theoretical physicists.
The XENON1T consists mainly of a tank with 3,500 kilos of liquid xenon at -95 degrees Celsius, submerged in turn in 700 cubic meters of ultrapure water. If a WIMP particle interacted with a xenon atom, it would produce flashes of light that can be captured, in theory, by the detector’s 248 photomultipliers, devices capable of registering the emission of a single photon.
