Featured Research

from universities, journals, and other organizations

Protons Pair Up With Neutrons: Finding Sheds New Light On Structure Of Nuclear Systems

Date:
June 3, 2008
Source:
DOE/Thomas Jefferson National Accelerator Facility
Summary:
New research has found that protons are about 20 times more likely to pair up with neutrons than with other protons in the nucleus. The result, based on the first-ever simultaneous measurement of such pairings and their constituents, could have implications for understanding the structure of nuclear systems from light nuclei to neutron stars.

Jefferson Lab's Experimental Hall A
Credit: Image courtesy of DOE/Thomas Jefferson National Accelerator Facility

Research performed at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility has found that protons are about 20 times more likely to pair up with neutrons than with other protons in the nucleus. The result will be published online by the journal Science, at the Science Express website.

The result, based on the first-ever simultaneous measurement of such pairings and their constituents, could have implications for understanding the structure of nuclear systems from light nuclei to neutron stars.

Protons and neutrons, or nucleons, in the nucleus of the atom can form a brief pairing with another nucleon, a phenomenon known as a short-range correlation. Previous experiments have shown that roughly one-fifth of nucleons at any one time were in short-range correlations.

Jefferson Lab Staff Scientist Douglas Higinbotham and his colleagues conducted an experiment in Jefferson Lab's Experimental Hall A to directly and simultaneously measure the constituents of the short-range correlations in the carbon nucleus.

"These correlated nucleons have a high relative momentum. If you knock one out one way, the correlated nucleon will fly out in the opposite direction," noted Higinbotham. "We set up our detectors to take advantage of this."

The experiment found that 18 percent of all protons in the nucleus were paired with neutrons. Another one percent of protons were paired with protons, with about the same percentage of neutron/neutron pairs.

"I think it shows, for the first time in a very clear and unambiguous way, this fact that the large momentum nucleons in nuclei are coming in pairs. And they're coming mainly in proton/neutron pairs," said Eli Piasetzky, a professor at Tel Aviv University and a spokesperson on the experiment.

Higinbotham agreed. "The result from this experiment is like finding that missing piece needed to finish a puzzle. This experiment, combined with others, gives us a very coherent picture of these short-range correlations in the nucleus."

In the experiment, a beam of energetic electrons was sent into a thin sheet (0.25 mm) of Carbon-12. The scientists were interested in the electrons that interacted with a member of a short-range correlation. Recoil electrons and knockout protons were measured in Jefferson Lab Experimental Hall A's High Resolution Spectrometers. Correlated protons and neutrons were measured in the BigBite large acceptance spectrometer and a neutron detector. The ability to clearly resolve the short-range correlated pairs is due to the high energy and large intensity beam at Jefferson Lab.

When combined with a theoretical calculation of the effects of proton/neutron correlations on the momentum distribution of the nucleons in neutron stars, the result also indicates that the presence of short-range correlations may have a disproportionately large effect on neutron star structure.

The experiment collaboration includes more than 60 members from 31 national and international institutions and was supported by the U.S. Department of Energy; the U.S. National Science Foundation; the Israel Science Foundation; the US-Israeli Bi-national Scientific Foundation; the UK Engineering and Physical Sciences Research Council and the Science & Technology Facilities Council.


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. Subedi et al. Probing Cold Dense Nuclear Matter. Science, Published online May 29 2008 DOI: 10.1126/science.1156675

Cite This Page:

DOE/Thomas Jefferson National Accelerator Facility. "Protons Pair Up With Neutrons: Finding Sheds New Light On Structure Of Nuclear Systems." ScienceDaily. ScienceDaily, 3 June 2008. <www.sciencedaily.com/releases/2008/05/080529141325.htm>.
DOE/Thomas Jefferson National Accelerator Facility. (2008, June 3). Protons Pair Up With Neutrons: Finding Sheds New Light On Structure Of Nuclear Systems. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2008/05/080529141325.htm
DOE/Thomas Jefferson National Accelerator Facility. "Protons Pair Up With Neutrons: Finding Sheds New Light On Structure Of Nuclear Systems." ScienceDaily. www.sciencedaily.com/releases/2008/05/080529141325.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