Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Missing: Electron antineutrinos; Reward: Understanding of matter-antimatter imbalance

08.03.2012
An international particle physics collaboration today announced its first results toward answering a longstanding question – how the elusive particles called neutrinos can appear to vanish as they travel through space.

The result from the Daya Bay Reactor Neutrino Experiment [link: http://dayawane.ihep.ac.cn/] describes a critical and previously unmeasured quality of neutrinos – and their antiparticles, antineutrinos – that may underlie basic properties of matter and explain why matter predominates over antimatter in the universe.

Embedded under a mountain near the China Guangdong Nuclear Power Group power plant about 55 kilometers from Hong Kong, the Daya Bay experiment used neutrinos emitted by powerful reactors to precisely measure the probability of an electron antineutrino transforming into one of the other neutrino types.

The results, detailed in a paper submitted to the journal Physical Review Letters, reveal that electron neutrinos transform into other neutrino types over a short distance and at a surprisingly high rate.

"Six percent of the electron antineutrinos emitted from the reactor transform over about two kilometers into another flavor of neutrino. Essentially they change identity," explains University of Wisconsin–Madison physics professor Karsten Heeger. [link: http://neutrino.physics.wisc.edu/heeger.php] Heeger is the U.S. manager for the Daya Bay antineutrino detectors.

Coincident with presentations by other principal investigators in the Daya Bay collaboration, Heeger is describing the results today in a talk at the Symposium on Electroweak Nuclear Physics, held at Duke University.

Neutrinos oscillate among three types or "flavors" – electron, muon, and tau – as they travel through space. Two of those oscillations were measured previously, but the transformation of electron neutrinos into other types over this distance (a so called "mixing angle" named theta one-three, written ?13) was unknown before the Daya Bay experiment.

"We expected that there would be such an oscillation, but we did not know what its probability would be," says Heeger.

The Daya Bay experiment counted the number of electron antineutrinos recorded by detectors in two experimental halls near the Daya Bay and Ling Ao reactors and calculated how many would reach the detectors in a more distant hall if there were no oscillation. The number that apparently vanished on the way – due to oscillating into other flavors – gave the value of theta one-three.

After analyzing signals of tens of thousands of electron antineutrinos emitted by the nuclear reactors, the researchers discovered that electron antineutrinos disappeared at a rate of six percent over the two kilometers between the near and far halls, a very short distance for a neutrino.

"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," says Yifang Wang of China's Institute of High Energy Physics, co-spokesperson and Chinese project manager of the Daya Bay experiment.

The value is unexpectedly large and helps explain why the experiment was able to make a precise measurement so quickly, with less than two months' worth of data from just six of the planned eight 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 and the University of California at Berkeley. Luk is co-spokesperson of the Daya Bay Experiment and heads U.S. participation.

The researchers confirmed the finding with very high confidence, Heeger says – in statistical terms, greater than five sigma, which translates to a less than a 1 in 3.5 million chance that the result arose by random chance.

The findings fill in a major gap in understanding neutrino oscillation and will provide important guidance for future neutrino experiments, including looking for nonstandard effects outside of current theories.

Under the guidance of U.S. chief project engineer Jeff Cherwinka, an engineer at the UW–Madison Physical Sciences Laboratory (PSL), the collaboration is now assembling the last two detectors and will install them this summer to increase data collection and improve precision. The UW–Madison PSL [link: http://www.psl.wisc.edu/projects/large/dayabay] and Department of Physics have been involved in designing and building the detectors since 2006.

"What made this possible is that the detectors worked really well. We have a very strong technical engineering team with PSL, which led the onsite assembly and installation of the detectors. This allowed us to come online ahead of schedule and make these measurements so quickly," Heeger says.

Heeger will also present the findings locally in a seminar at 3:00 p.m. on Mar. 13 in 4272 Chamberlin Hall on the UW–Madison campus.

The Daya Bay collaboration is jointly led by China and the United States, with additional participants from Russia, the Czech Republic, Hong Kong, and Taiwan.

More information, including the submitted paper and photos of the experiment, are available at http://neutrino.physics.wisc.edu/dayabatheta13.

Karsten Heeger | EurekAlert!
Further information:
http://www.wisc.edu

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 >>>

Anzeige

Anzeige

VideoLinks
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

VideoLinks
Science & Research
Overview of more VideoLinks >>>