Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Announcing the first results from Daya Bay: Discovery of a new kind of neutrino transformation

Knowing how different kinds of neutrinos mix and change could reveal their masses, explore differences between neutrinos and antineutrinos, and explain why there is any matter at all in the universe

The Daya Bay Reactor Neutrino Experiment, a multinational collaboration operating in the south of China, today reported the first results of its search for the last, most elusive piece of a long-standing puzzle: how is it that neutrinos can appear to vanish as they travel?

Each antineutrino detector at the Daya Bay Reactor Neutrino Experiment is lined with photomultiplier tubes to catch the faint trace of antineutrino reactions in the scintillator fluids that fill the detectors. Credit: Roy Kaltschmidt, Lawrence Berkeley National Laboratory

The surprising answer opens a gateway to a new understanding of fundamental physics and may eventually solve the riddle of why there is far more ordinary matter than antimatter in the universe today.

Traveling at close to the speed of light, the three basic neutrino "flavors" – electron, muon, and tau neutrinos, as well as their corresponding antineutrinos – mix together and oscillate (transform), but this activity is extremely difficult to detect. From Dec. 24, 2011, until Feb. 17, 2012, scientists in the Daya Bay collaboration observed tens of thousands of interactions of electron antineutrinos, caught by six massive detectors buried in the mountains adjacent to the powerful nuclear reactors of the China Guangdong Nuclear Power Group. These reactors, at Daya Bay and nearby Ling Ao, produce millions of quadrillions of elusive electron antineutrinos every second.

The copious data revealed for the first time the strong signal of the effect that the scientists were searching for, a so called "mixing angle" named theta one-three (written è13), which the researchers measured with unmatched precision. Theta one-three, the last mixing angle to be precisely measured, expresses how electron neutrinos and their antineutrino counterparts mix and change into the other flavors. The Daya Bay collaboration's first results indicate that sin2 2 è13 is equal to 0.092 plus or minus 0.017.

"This is a new type of neutrino oscillation, and it is surprisingly large," says Yifang Wang of China's Institute of High Energy Physics (IHEP), co-spokesperson and Chinese project manager of the Daya Bay experiment. "Our precise measurement will complete the understanding of the neutrino oscillation and pave the way for the future understanding of matter-antimatter asymmetry in the universe."

Neutrinos, the wispy particles that flooded the universe in the earliest moments after the big bang, are continually produced in the hearts of stars and other nuclear reactions. Untouched by electromagnetism, they respond only to the weak nuclear force and even weaker gravity, passing mostly unhindered through everything from planets to people. The challenge of capturing these elusive particles inspired the Daya Bay collaboration in the design and precise placement of its detectors.

"Although we're still two detectors shy of the complete experimental design, we've had extraordinary success in detecting the number of electron antineutrinos that disappear as they travel from the reactors to the detectors two kilometers away," says Kam-Biu Luk of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley. Luk is co-spokesperson of the Daya Bay Experiment and heads U.S. participation. "What we didn't expect was the sizable disappearance, equal to about six percent. Although disappearance has been observed in another reactor experiment over large distances, this is a new kind of disappearance for the reactor electron antineutrino."

The Daya Bay experiment counts the number of electron antineutrinos detected in the halls nearest the Daya Bay and Ling Ao reactors and calculates how many would reach the detectors in the Far Hall if there were no oscillation. The number that apparently vanish on the way (oscillating into other flavors, in fact) gives the value of theta one-three. Because of the near-hall/far-hall arrangement, it's not even necessary to have a precise estimate of the antineutrino flux from the reactors.

"Even with only the six detectors already operating, we have more target mass than any similar experiment, plus as much or more reactor power," says William Edwards of Berkeley Lab and UC Berkeley, the U.S. project and operations manager for the Daya Bay Experiment. Since Daya Bay will continue to have an interaction rate higher than any other experiment, Edwards explains, "it is the leading theta one-three experiment in the world."

The first Daya Bay results show that theta one-three, once feared to be near zero, instead is "comparatively huge," Kam-Biu Luk remarks, adding that "Nature was good to us." In coming months and years the initial results will be honed by collecting far more data and reducing statistical and systematic errors.

"The Daya Bay experiment plans to stop the current data-taking this summer to install a second detector in the Ling Ao Near Hall, and a fourth detector in the Far Hall, completing the experimental design," says Yifang Wang.

Refined results will open the door to further investigations and influence the design of future neutrino experiments – including how to determine which neutrino flavors are the most massive, whether there is a difference between neutrino and antineutrino oscillations, and, eventually, why there is more matter than antimatter in the universe – because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.

"It has been very gratifying to be able to work with such an outstanding international collaboration at the world's most sensitive reactor neutrino experiment," says Steve Kettell of Brookhaven National Laboratory, the chief scientist for the U.S. effort. "This moment is exciting because we have finally observed all three mixing angles, and now the way is cleared to explore the remaining parameters of neutrino oscillation."

"This is really remarkable," says Wenlong Zhan, vice president of the Chinese Academy of Sciences and president of the Chinese Physical Society. "We hoped for a positive result when we decided to fund the project, but we never imagined it could come so quickly!"

"Exemplary teamwork among the partners has led to this outstanding performance," says James Siegrist, DOE Associate Director of Science for High Energy Physics. "These notable first results are just the beginning for the world's foremost reactor neutrino experiment."

The Daya Bay collaboration consists of scientists from the following countries and regions: China, the United States, Russia, the Czech Republic, Hong Kong, and Taiwan. The Chinese effort is led by co-spokesperson, chief scientist, and project manager Yifang Wang of the Institute of High Energy Physics, and the U.S. effort is led by co-spokesperson Kam-Biu Luk and project and operations manager William Edwards, both of Berkeley Lab and UC Berkeley, and by chief scientist Steve Kettell of Brookhaven.

Contact information:

Yifang Wang, co-spokesperson, IHEP, +86-10-88236076,

Kam-Biu Luk, co-spokesperson, Berkeley Lab and UC Berkeley, 510 486-7054, 510-642-8162,

Tongzhou Xu, IHEP Public Affairs, +86-10-88235008,

Paul Preuss, Berkeley Lab Public Affairs, 510-486-6249,

Justin Eure, Brookhaven Public Affairs, 631-344-2347,

The collaborating institutions of the Daya Bay Reactor Neutrino Experiment are Beijing Normal University, Brookhaven National Laboratory, California Institute of Technology, Charles University in Prague, Chengdu University of Technology, China Guangdong Nuclear Power Group, China Institute of Atomic Energy, Chinese University of Hong Kong, Dongguan University of Technology, Joint Institute for Nuclear Research, University of Hong Kong, Institute of High Energy Physics, Illinois Institute of Technology, Iowa State University, Lawrence Berkeley National Laboratory, Nanjing University, Nankai University, National Chiao-Tung University, National Taiwan University, National United University, North China Electric Power University, Princeton University, Rensselaer Polytechnic Institute, Shandong University, Shanghai Jiao Tong University, Shenzhen University, Siena College, Tsinghua University, University of California at Berkeley, University of California at Los Angeles, University of Cincinnati, University of Houston, University of Illinois at Urbana-Champaign, University of Science and Technology of China, Virginia Polytechnic Institute and State University Blacksburg, University of Wisconsin-Madison, College of William and Mary, and Sun Yat-Sen (Zhongshan) University.

For more information, visit

Paul Preuss | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Physicists edge closer to controlling chemical reactions
11.12.2018 | Moscow Institute of Physics and Technology

nachricht UA-led OSIRIS-REx discovers water on asteroid, confirms Bennu as excellent mission target
11.12.2018 | University of Arizona

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

Im Focus: Substitute for rare earth metal oxides

New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals

Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.

Im Focus: A bit of a stretch... material that thickens as it's pulled

Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.

Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...

Im Focus: The force of the vacuum

Scientists from the Theory Department of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science (CFEL) in Hamburg have shown through theoretical calculations and computer simulations that the force between electrons and lattice distortions in an atomically thin two-dimensional superconductor can be controlled with virtual photons. This could aid the development of new superconductors for energy-saving devices and many other technical applications.

The vacuum is not empty. It may sound like magic to laypeople but it has occupied physicists since the birth of quantum mechanics.

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

Expert Panel on the Future of HPC in Engineering

03.12.2018 | Event News

Latest News

Some brain tumors may respond to immunotherapy, new study suggests

11.12.2018 | Studies and Analyses

Researchers image atomic structure of important immune regulator

11.12.2018 | Health and Medicine

Physicists edge closer to controlling chemical reactions

11.12.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>