Even for a particle physicist, Janet Conrad thinks small. Early in her career, when her peers were fanning out in search of the top quark, now known to be the heaviest elementary particle, she broke ranks to seek out the neutrino, the lightest.
In part, she did this to avoid working as part of a large collaboration, demonstrating an independent streak shared by the particles she studies. Neutrinos eschew the strong and electromagnetic forces, maintaining only the most tenuous of ties to the rest of the universe through the weak force and gravity. This aloofness makes neutrinos hard to study, but it also allows them to serve as potential indicators of forces or particles entirely new to physics, according to Conrad, a professor at the Massachusetts Institute of Technology. “If there’s a force out there we haven’t seen, it must be because it is very, very weak — very quiet. So looking at a place where things are only whispering is a good idea.”
In fact, neutrinos have already hinted at the existence of a new type of whispery particle. Neutrinos come in three flavors, morphing from one flavor to another by means of some quantum jujitsu. In 1995, the Liquid Scintillator Neutrino Detector (LSND) at Los Alamos National Laboratory suggested that these oscillations involve more than the three flavors “we knew and loved,” Conrad said. Could there be another, more elusive type of “sterile” neutrino that can’t feel even the weak force? Conrad has been trying to find out ever since, and she expects to get the latest result from a long-running follow-up experiment called MiniBooNE within a year.
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