Featured Research

from universities, journals, and other organizations

More Precise Solar Neutrino Production Figure Determined By University Of Washington Scientists

Date:
January 29, 2002
Source:
University Of Washington
Summary:
Scientists working at huge underground laboratories in Japan and Canada have made major strides in understanding neutrinos during the last three years. Now a team working with a particle accelerator at the University of Washington has added another significant finding, determining with the greatest precision yet just how many energetic neutrinos are generated in the sun's nuclear furnace.

Neutrinos are among the tiniest particles in the universe. They're also among the more perplexing problems physicists face.

Scientists working at huge underground laboratories in Japan and Canada have made major strides in understanding neutrinos during the last three years. Now a team working with a particle accelerator at the University of Washington has added another significant finding, determining with the greatest precision yet just how many energetic neutrinos are generated in the sun's nuclear furnace.

They found that the fusion rate producing those subatomic particles in the sun is 17 percent greater than previously thought, said Kurt Snover, a UW research professor in physics who heads the team. And, he added, the new number is accurate to within 3 or 4 percentage points, compared to 15 points for the old standard. The findings mean the sun must be producing 17 percent more energetic neutrinos (the highest-energy solar neutrinos) than scientists previously thought.

The research, published in the Jan. 28 edition of Physical Review Letters, was done by Snover, Arnd Junghans, Erik Mohrmann, Tom Steiger, Eric Adelberger, Jean-Marc Casandjian and Erik Swanson, all of the UW Center for Experimental Nuclear Physics and Astrophysics. Also taking part were Lothar Buchman, Sehwan Park and Alex Zyuzin from Canada's national particle and nuclear physics laboratory in Vancouver, British Columbia.

Neutrinos come from several natural sources. The highest-energy neutrinos are produced by cosmic rays outside the solar system, while solar neutrinos have lower energies. Either way, the particles come in three types – what physicists call "flavors" – electron, muon and tau. A fourth type, called a sterile neutrino, also could be a factor.

Experiments at the Super-Kamiokande detector in Japan and the Sudbury Neutrino Observatory in Canada in the last three years have shown that these particles can change from one flavor to another, proof that neutrinos have mass. That finding is important for researchers trying to find the so-called "missing mass" of the universe, mass that is theorized to have resulted from the Big Bang but which so far has been unaccounted for.

For more than two decades there has been a physics problem associated with solar neutrinos. An experiment begun in 1965 at Homestake Gold Mine in South Dakota proved that the particles were bombarding Earth, but at far lower levels than expected.

"People didn't know if the calculations of how many neutrinos coming from the sun was wrong, whether there was a problem with the experiment or a third possibility, that neutrinos traveling from the sun changed their character," Snover said.

Together, the Sudbury and Super-Kamiokande experiments demonstrated the third possibility was the correct one. All solar neutrinos start in the electron "flavor," but the two underground experiments showed that some of those change to the tau or muon varieties, and that the total of all three varieties coming from the sun totals roughly what physicists would expect to see.

The solar neutrino production rate, determined from calculations performed at other institutions, is figured from the sun's temperature; the amounts of beryllium, hydrogen, helium and other materials used for fuel; and the rates at which the materials combine with each other, including the fusion rate of beryllium-7 with hydrogen.

"We determined this fusion rate much more precisely with our experiment," Snover said.

The UW team used a particle accelerator to fire protons (nuclei of hydrogen atoms) in a particle beam at a tiny piece of beryllium-7, a radioactive metal isotope. In the experiment, the beryllium-7 is held on a rotating arm that moves the metal in front of the particle beam, where it is bombarded by high-speed protons and transformed into boron-8. The arm then quickly swings the metal fragment in front of a detector that verifies that boron-8 has been produced. From there the scientists deduce neutrino production, since the new isotope has a half-life of less than a second before it gives off a neutrino. By studying the boron-8 production in the experiment, Snover's group is able to determine a key factor in calculating the solar neutrino production rate.

The U.S. Department of Energy and the Natural Sciences and Engineering Research Council of Canada finance the work, which is a step in improving the understanding of particle physics.

"It helps us understand better the differences in mass, as well as other properties, among these character-changing neutrinos," Snover said.

"It's factors like these that go into the soup pot when you're trying to figure out what are the properties of a neutrino."


Story Source:

The above story is based on materials provided by University Of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University Of Washington. "More Precise Solar Neutrino Production Figure Determined By University Of Washington Scientists." ScienceDaily. ScienceDaily, 29 January 2002. <www.sciencedaily.com/releases/2002/01/020129073111.htm>.
University Of Washington. (2002, January 29). More Precise Solar Neutrino Production Figure Determined By University Of Washington Scientists. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2002/01/020129073111.htm
University Of Washington. "More Precise Solar Neutrino Production Figure Determined By University Of Washington Scientists." ScienceDaily. www.sciencedaily.com/releases/2002/01/020129073111.htm (accessed October 20, 2014).

Share This



More Space & Time News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com
Latin America Launches Communications Satellite

Latin America Launches Communications Satellite

AFP (Oct. 17, 2014) Argentina launches a home-built satellite, a first for Latin America. It will ride a French-made Ariane 5 rocket into orbit, and will provide cell phone, digital TV, Internet and data services to the lower half of South America. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
This Week @ NASA, October 17, 2014

This Week @ NASA, October 17, 2014

NASA (Oct. 17, 2014) Power spacewalk, MAVEN’s “First Light”, Hubble finds extremely distant galaxy and more... Video provided by NASA
Powered by NewsLook.com
Saturn's 'Death Star' Moon Might Have A Hidden Ocean

Saturn's 'Death Star' Moon Might Have A Hidden Ocean

Newsy (Oct. 17, 2014) The smallest of Saturn's main moons, Mimas, wobbles as it orbits. Research reveals it might be due to a global ocean underneath its icy surface. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins