The Next Big Physics Machines Are Neutrino Detectors
Now that the Large Hadron Collider has apparently found the Higgs Boson, a sort of malaise set over some of the scientists behind the project. What do you do next with a 17-mile underground ring? And will there be a successor—an even larger collider of hadrons?
Fear not, lovers of big physics machines. While we await that answer, multiple new mega-projects are coming in the form of sprawling neutrino detectors, according to neutrino scientists who spoke at this weekend’s meeting of the American Association for the Advancement of Science in Boston. China’s building them, Japan is vying for an even larger one that it already has, and the U.S.’s Fermilab, outside Chicago, hopes to start firing neutrinos toward a detector 800 miles away near Mount Rushmore.
Neutrinos are the second smallest known particle (six orders of magnitude smaller than an electron!). The sun creates them. Supernovas create them. The Earth gives off its own. Physicists are fond of reminding people that billions of these ghostly particles pass through your body all the time. But therein lies the problem: Neutrinos interact with ordinary matter so little that they are impossible to detect directly. That is why you need such big machines. To detect neutrinos, physicists frequently have used a big tank of water (or mass of ice) with a batch of photomultipliers. Most neutrinos pass right through the water without interacting with anything, but every now and then one strikes the nucleus of an atom. The particle that’s then released travels faster than light (within the water medium, where the speed of light is slightly slower than normal—this is now the process doesn’t violate the laws of physics.) It creates what’s called Cherenkov radiation, which is how scientists know a neutrino came through. They can also start to figure out its energy level and the direction it came from.
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