For more than a decade, the particle physics community has faced a perplexing puzzle: two experiments, LSND at Los Alamos and MiniBooNE at Fermilab, found hints of neutrino behavior that did not fit the usual assumption that the universe contains three types of neutrinos that have tiny masses and oscillate.
The data from these two experiments suggest that something unusual is going on when low-energy muon neutrinos travel a short distance, less than a kilometer. The answer might be that there are additional types of neutrinos, albeit with properties different from the three “normal” types. These extras are known as sterile neutrinos. A confirmed discovery of a sterile neutrino would open up a whole new world of particles previously hidden from view.
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