Subscribe free to our newsletters via your
. 24/7 Space News .

Experiment Observes Elusive Neutrino Transformation
by Marcus Woo for Caltech News
Pasadena CA (SPX) Mar 12, 2012

This image is a glimpse into the depths of a neutrino detector that's part of the Daya Bay Neutrino Experiment. Each detector consists of two inner nested transparent acrylic cylinders that sit inside a third vessel made of stainless steel. When filled with clear liquid scintillator, the detectors will reveal antineutrino interactions by emitting very faint flashes of light. Sensitive photomultiplier tubes line the detector walls, ready to amplify and record the telltale flashes. [Credit: Roy Kaltschmidt, Lawrence Berkeley National Laboratory].

An international team of physicists-including several from the California Institute of Technology (Caltech)-has detected and measured, for the first time, a transformation of one particular type of neutrino into another type. The finding, physicists say, may help solve some of the biggest mysteries about the universe, such as why the universe contains more matter than antimatter-a phenomenon that explains why stars, planets, and people exist at all.

The results, released online on March 8, come from the Daya Bay Reactor Neutrino Experiment, which consists of six 20-ton neutrino detectors lying beneath the mountains of southern China near Hong Kong. The paper in which the team reports its data has been submitted to the journal Physical Review Letters.

"Physicists working on five experiments around the world have been racing to measure this process," says Robert McKeown, professor of physics and leader of the Caltech team involved with the project. "Our precise measurement from the Daya Bay Experiment now provides the final clue in helping us understand neutrino transformations."

Neutrinos are fundamental, uncharged particles that zip through space at near-light speed, barely interacting with any other particles. In fact, billions of neutrinos are streaming through your body at this very second.

Neutrinos come in three types (or "flavors")-electron, muon, and tau-and can transform from one type to another via a process that is described by variables called mixing angles. There are three mixing angles, two of which have been previously measured; McKeown was part of the KamLAND experiment in Japan that helped determine the second of these mixing angles several years ago.

But an accurate measurement of the third, called theta 13 ("theta one three"), which describes how an electron neutrino transforms into the other flavors, has eluded physicists. Thanks to the Daya Bay Experiment, physicists have finally pinned down a precise number to describe the transformation.

Having measured all three mixing angles, physicists can now pursue the next set of ambitious experiments to study what is called CP violation, or charge-conjugation and parity violation, says McKeown. If CP violation is true, then particle reactions can occur at rates that differ from those of reactions involving the particles' antimatter counterparts.

In theory, the Big Bang should have produced equal amounts of matter and antimatter, with collisions between the two subsequently annihilating both. Had that been the case, however, there would be no stars, planets, people, or anything else made of matter. But CP violation, the thought goes, enabled the universe to have more matter than antimatter.

The Daya Bay Reactor Neutrino Experiment's six liquid-filled cylinders detect antineutrinos-the antimatter partner of the neutrino-produced by nuclear reactors in the nearby China Guangdong Nuclear Power Group. Three neutrino detectors sit about 400 meters (about a quarter of a mile) from the nuclear reactors, while the other three are located about 1700 meters (just over a mile) away.

The nuclear reactions that occur inside the energy-producing reactors produce electron antineutrinos, which can be observed by both sets of detectors. The far set of detectors measure fewer electron antineutrinos than expected because a fraction of the electron antineutrinos transform into muon and tau antineutrinos in mid-flight.

The detectors cannot directly observe these muon or tau antineutrinos, but by measuring the fraction of "missing" electron antineutrinos, researchers can determine the Theta 13 mixing angle. In their experiments, the physicists found that the far set of detectors observed 6 percent fewer electron antineutrinos than expected, giving them the information needed to precisely calculate the value of Theta 13-which turned out to be 8.8 degrees.

McKeown and the Caltech group designed and built the calibration devices (three for each detector) that enabled their colleagues to understand how well the detectors would work and other crucial properties of the instruments.

The other Caltech members of the Daya Bay Collaboration are staff scientist Robert Carr, senior postdoctoral scholar in physics Dan Dwyer, Robert A. Millikan Postdoctoral Scholar in Experimental Physics Xin Qian, graduate student Hei Man (Raymond) Tsang, and postdoctoral scholar in physics Fenfang Wu.


Related Links
Understanding Time and Space

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Antimatter zapped
Geneva, Switzerland (SPX) Mar 08, 2012
First it was caught. Then it was stored. And now it is being made to jump. "It" is the elusive antihydrogen atom. Researchers at CERN, in an international effort led by a Canadian team, have used microwaves to manipulate antihydrogen atoms. In doing so, they've provided the world with its first glimpse of an "anti-atomic fingerprint." Their work is published in the prestigious journal Nature, fo ... read more

Apollo 11: 'A Stark Beauty All Its Own'

Magnetic moon

Twin GRAIL Spacecraft Begin Collecting Lunar Science Data

Apollo 12: Pinpoint Landing on the Ocean of Storms

Rep. Schiff Applauds Decision to Reject NASA Request to Divert Mars Funds

Winter Studies of 'Amboy' Rock Continue

NASA Mars Orbiter Catches Twister in Action

Working models for the gravitational field of Phobos

SciTechTalk: Rembering a space 'Pioneer'

Tile Makers Creating Orion Shield

Weird and wonderful gadgets wow world's top IT fair

O, Pioneers! (part 2): The Derelicts of Space

Three for Tiangong

China hopes to send Long March-5 rocket into space in 2014

Upgraded carrier rocket ready for China's first manned space docking

Long March 7 carrier rocket to lift off in five years

ISS Plays Role in Vaccine Development

Though Shuttle Retired, ISS Still Open For Business, Research Going Strong

New date set for Europe's resupply mission to ISS

A New Website Sharing ISS Benefits For Humanity

ILS Announces A New Contract For The ILS Proton Launch Of The Mexsat-1 Satellite

Launch Madness at Wallops in March - "Five in Five"

Engineers Tuck NuSTAR in its Nose Cone

Lockheed Martin Selects Alaska's Kodiak Launch Complex To Support Future Athena Launches

Stars with Dusty Disks Should Harbor Earth-like Worlds

Star Comb joins quest for Earth-like planets

Researchers say galaxy may swarm with 'nomad planets'

New model provides different take on planetary accretion

Garafolo tests spacecraft seal to verify computer models

Andrews Space Contracted to Deliver 100 Series Command and Data Handling System for GEO Application

Astrium wins Helios through life support contract extension

Researchers 'Print' Polymers That Bend Into 3-D Shapes

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement