Featured Research

from universities, journals, and other organizations

Moving Quarks Help Solve Proton Spin Puzzle

Date:
September 16, 2008
Source:
DOE/Thomas Jefferson National Accelerator Facility
Summary:
New theory work at the US Department of Energy's Thomas Jefferson National Accelerator Facility has shown that more than half of the spin of the proton is the result of the movement of its building blocks: quarks. The result, published in Physical Review Letters, agrees with recent experiments and supercomputer calculations.

New theory work at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has shown that more than half of the spin of the proton is the result of the movement of its building blocks: quarks. The result agrees with recent experiments and supercomputer calculations.

Related Articles


It was thought that the spin of the proton would come from its quarks, but experiments beginning with the European Muon Collaboration in the 1980s have established that the quarks' spin accounts for only one third of the proton's spin. Researchers thus began investigating other sources of the proton’s spin.

This research concerns one theoretical model, proposed by Jefferson Lab Chief Scientist Tony Thomas and University of South Carolina Professor Fred Myhrer, that suggests that some of the proton’s spin is actually generated as orbital angular momentum by its quarks.

“Rather than the way the quarks are spinning, it's the way they're moving in orbital motion. In fact, more than half of the spin of the proton is orbital motion of the quarks. That's a really fascinating thing,” Thomas said.

In this paper, Thomas explored the model’s predictions further by extracting more detailed information, including how the orbital angular momentum is generated by the different quarks inside the proton, which has two up quarks and one down quark.

He found that the model seemed to contradict experimental results and the results from highly sophisticated supercomputer calculations of quark behavior, called lattice QCD. The model showed that up quarks carried most of the proton’s spin, whereas experiment and lattice QCD point to down quarks.

Thomas said it turns out that the disagreement is only a matter of resolution. The only way to relate such models to the underlying theory of quark interactions is to assume the model’s predictions are made at low resolution. However, experiment and supercomputer calculations are made at high resolution.

“In the past, there's been tremendous success starting with the quark model at some very low scale, and then evolving to a higher scale, where you can compare with experiment,” Thomas explained. “If you make that generally accepted assumption, then the resulting high-resolution values are in surprisingly good agreement with state-of-the-art lattice QCD calculations, as well as with recent experiments conducted at Hermes and Jefferson Lab. There is a remarkable degree of consistency.”

The next step is to compare the model with results from upcoming, more detailed measurements of the orbital angular momentum of the quarks in the proton.


Story Source:

The above story is based on materials provided by DOE/Thomas Jefferson National Accelerator Facility. Note: Materials may be edited for content and length.


Journal Reference:

  1. Thomas et al. Interplay of Spin and Orbital Angular Momentum in the Proton. Physical Review Letters, 2008; 101 (10): 102003 DOI: 10.1103/PhysRevLett.101.102003

Cite This Page:

DOE/Thomas Jefferson National Accelerator Facility. "Moving Quarks Help Solve Proton Spin Puzzle." ScienceDaily. ScienceDaily, 16 September 2008. <www.sciencedaily.com/releases/2008/09/080912101402.htm>.
DOE/Thomas Jefferson National Accelerator Facility. (2008, September 16). Moving Quarks Help Solve Proton Spin Puzzle. ScienceDaily. Retrieved December 22, 2014 from www.sciencedaily.com/releases/2008/09/080912101402.htm
DOE/Thomas Jefferson National Accelerator Facility. "Moving Quarks Help Solve Proton Spin Puzzle." ScienceDaily. www.sciencedaily.com/releases/2008/09/080912101402.htm (accessed December 22, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Monday, December 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Will New A350 Help Airbus Fly?

Will New A350 Help Airbus Fly?

Reuters - Business Video Online (Dec. 22, 2014) Qatar Airways takes first delivery of Airbus' new A350 passenger jet. As Joel Flynn reports it's the planemaker's response to the Boeing 787 Dreamliner and the culmination of eight years of development. Video provided by Reuters
Powered by NewsLook.com
Man Parachutes Off Lawn Chair Airlifted By Helium Balloons

Man Parachutes Off Lawn Chair Airlifted By Helium Balloons

Buzz60 (Dec. 22, 2014) A BASE jumper rides a lawn chair, a shotgun, and a giant bunch of helium balloons into the sky in what seems like a country version of the movie 'Up." Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Touch-Free Smart Phone Empowers Mobility-Impaired

Touch-Free Smart Phone Empowers Mobility-Impaired

Reuters - Innovations Video Online (Dec. 21, 2014) A touch-free phone developed in Israel enables the mobility-impaired to operate smart phones with just a movement of the head. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Existing Chemical Compounds Could Revive Failing Antibiotics, Says Danish Scientist

Existing Chemical Compounds Could Revive Failing Antibiotics, Says Danish Scientist

Reuters - Innovations Video Online (Dec. 21, 2014) A team of scientists led by Danish chemist Jorn Christensen says they have isolated two chemical compounds within an existing antipsychotic medication that could be used to help a range of failing antibiotics work against killer bacterial infections, such as Tuberculosis. Jim Drury went to meet him. Video provided by Reuters
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