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Berkeley
Lab physicists and engineers are among the leaders of the unique Daya
Bay Reactor Neutrino Experiment, where Chinese and American scientists,
with colleagues from Russia, Taiwan, and the Czech Republic, have come
together to investigate a peculiar phenomenon related to so-called
neutrino mixing. Kam-Biu Luk of Berkeley Lab’s Physics Division, a
professor of physics at the University of California at Berkeley, is
Daya Bay’s scientific co-spokesperson with Yifang Wang of Beijing’s
Institute of High Energy Physics. Bill Edwards of the Lab’s Physics
Division is the U.S. Project and Operations Manager.
What
the researchers find at Daya Bay 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 ?13, 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. The following tour of
the experimental site shows how the researchers hope to do it.
