The Daya Bay Reactor Neutrino Experiment brings Chinese and American scientists together with colleagues from Russia, Taiwan, and the Czech Republic to investigate perhaps the most important unanswered question relating to the phenomenon of neutrino oscillation. What they find will bear on some of the most intriguing questions in basic physics. How much do different kinds of neutrinos weigh? And which kind is the heaviest?
By weighing neutrinos, scientists hope to learn how electrons and their cousins, muons and tau particles, came into existence in the moments after the big bang. The answers could explain why there is more matter than antimatter in the universe – and indeed why there is any matter at all.
Clues to neutrino mass lie in measuring how one “flavor” of neutrino changes into another. (Electron neutrinos, muon neutrinos, and tau neutrinos, the three flavors, are named after the leptons with which each is associated.) The crucial value, written θ13, is a term known as “neutrino mixing angle theta one three” – and the Daya Bay experiment is intended to measure it to within a few degrees.
Yifang Wang of Beijing’s Institute of High Energy Physics and Kam-Biu Luk of Lawrence Berkeley National Laboratory, a professor of physics at the University of California at Berkeley, are Daya Bay’s scientific co-spokespersons. Berkeley Lab’s Bill Edwards is the U.S. Project and Operations Manager.
This tour of the experimental site, with photographs by Berkeley Lab’s Roy Kaltschmidt, shows how the researchers hope to trap enough neutrinos to answer their questions.
