Featured Research

from universities, journals, and other organizations

Strange Quark Contribution To Proton Structure Yields Surprising Result

Date:
December 18, 2000
Source:
University Of Illinois At Urbana-Champaign
Summary:
Scientists seeking to confirm earlier measurements of the strange quark's contribution to the proton's magnetic moment have found several surprises, instead.

CHAMPAIGN, Ill. — Scientists seeking to confirm earlier measurements of the strange quark's contribution to the proton's magnetic moment have found several surprises, instead.

As reported in the Dec.15 issue of the journal Science, physicists who combined results from two measurements have calculated a lower strange quark contribution, and provided evidence for the existence of a parity-violating electromagnetic effect known as the proton's anapole moment.

In experiments with the SAMPLE apparatus at the MIT/Bates Linear Accelerator Center, scientists used the weak magnetic force to uncover the contributions of the up, down and strange quarks. "The parity-violating nature of the weak force provides a powerful tool to unravel the internal structure of the proton," said Doug Beck, a physics professor at the University of Illinois and a collaborator on SAMPLE. "The basic idea is to study the preference for the proton's interaction with electrons spinning counterclockwise, over those spinning clockwise." In the first SAMPLE experiment, the parity-violating asymmetry of the proton was measured by scattering an intense beam of electrons off a liquid hydrogen target. In the second experiment – conducted during the summer of 1999 – the hydrogen target was replaced with deuterium. By scattering electrons off both protons and neutrons, the researchers could examine – and solve – different linear combinations. While results from the initial experiment indicated a potentially large contribution from the strange quark, the second experiment "brought that number down considerably," Beck said. "The new results imply that less than 6 percent of the proton's magnetic moment arises from the strange quark."

The difference in values between the two experiments, the scientists say, is due to the presence of a surprisingly large anapole moment of the proton – an effect long predicted, but never measured. "The proton's anapole moment is not yet well understood, but could have important implications for precision weak interaction studies in atomic systems such as cesium," Beck said. The spatial dependence of the strange quark contributions will be studied in detail in an upcoming program of parity-violation measurement at the Thomas Jefferson National Accelerator Facility. For that series of experiments, a special toroidal superconducting magnet – funded by the National Science Foundation – has been constructed and is currently being tested at the UI. "The new magnet should allow measurement of the anapole moment with much greater precision over a wide range of momentum transfers," Beck said. "Instead of seeing the proton's overall magnetic moment, we will be able to vary the size of our probe to study small structures within the proton."

The SAMPLE experiment is a collaboration involving the UI, Argonne National Lab, California Institute of Technology, University of Kentucky, Louisiana Tech University, University of Maryland, Massachusetts Institute of Technology, College of William and Mary, and Virginia Polytechnic Institute and State University.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Strange Quark Contribution To Proton Structure Yields Surprising Result." ScienceDaily. ScienceDaily, 18 December 2000. <www.sciencedaily.com/releases/2000/12/001218073524.htm>.
University Of Illinois At Urbana-Champaign. (2000, December 18). Strange Quark Contribution To Proton Structure Yields Surprising Result. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2000/12/001218073524.htm
University Of Illinois At Urbana-Champaign. "Strange Quark Contribution To Proton Structure Yields Surprising Result." ScienceDaily. www.sciencedaily.com/releases/2000/12/001218073524.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
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:
from the past week

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