The major hurdle for scientists who study the internal structure of the neutron is that most neutrons are bound up inside the nucleus of atoms to protons. In nature, a free neutron lasts for only a few minutes, while in the nucleus, neutrons are always encumbered by the ubiquitous proton.
To tease out a description of a free neutron, a group of scientists compared data collected at Jefferson Lab and the SLAC National Accelerator Laboratory that detail how bound protons and neutrons in the nucleus of the atom display two very different effects. Both protons and neutrons are referred to as nucleons.
"Both effects are due to the nucleons behaving like they are not free," says Doug Higinbotham, a Jefferson Lab staff scientist.
Nucleons appear to differ when they are tightly bound in heavier nuclei versus when they are loosely bound in light nuclei. In the first effect, experiments have shown that nucleons tightly bound in a heavy nucleus pair up more often than those loosely bound in a light nucleus.
"The first thing was the probability of finding two nucleons close together in the nucleus, what we call a short-range correlation," says Larry Weinstein, a professor at Old Dominion University. "And the probability that the two nucleons are in a short-range correlation increases as the nucleus gets heavier."
Meanwhile, other experiments have shown a clear difference in how the proton's building blocks, called quarks, are distributed in heavy nuclei versus light nuclei. This difference is called the EMC Effect.
"People were measuring and discussing the EMC effect. And people were discussing things about the short-range correlations effect. Nobody bothered to look to see if there's any connection between them," adds Eliezer Piasetzky, a professor at Tel Aviv University in Israel.
When the group combined the data from a half-dozen experiments regarding these two different effects on one graph, they found that the two effects were correlated.
"Take a quantity that tells you how strong the EMC Effect is. And then take another quantity that tells you how many short-range correlations you have," Higinbotham explains. "And you see that when one is big, the other one is big. When one is small, the other one is small."
The scientists say that it's unlikely that one effect causes the other. Rather, the data shows that there is a common cause for both.
"I think that we certainly agree that from the position picture, it's due to nucleons overlapping that is causing this. And in the momentum picture, it is the high-momentum nucleons that are causing this. And, of course, it's quantum mechanics, so choose your picture," Higinbotham explains.
The group says the common cause may have remained a mystery for so long, because while the two effects they are studying are obviously related when laid out on a graph, the connection was previously obscured by the different, yet related ways in which the two effects are studied.
"When you do a measurement for the EMC Effect, what you do is you look inside the nucleon. You break open the nucleon and see inside. What happens inside the nucleon is very different from the short-range correlations, which is what happens between two different nucleons," Piasetzky says.
"What's very new here is that we have linked two fields that were completely disconnected. So now you can start asking questions about what that connection can help us learn," Higinbotham says.
They say the next step is to further compare the data from all of the source experiments that they used in their analysis to see if data for one effect may now be used to learn something new about the other. Then, of course, they'd like to use the knowledge that the two effects are connected to design new experiments for shining a light on other secrets buried in the nucleus of the atom.
This work was supported in part by the DOE Office of Science, the National Science Foundation, the Israel Science Foundation, and the U.S.-Israeli Bi-National Science Foundation.
Jefferson Lab is managed and operated for the U.S. Department of Energy's Office of Science by Jefferson Science Associates, LLC, a joint venture between Southeastern Universities Research Association, Inc. and CSC Applied Technology Group, LLC.
Contact: Kandice Carter, Jefferson Lab Public Affairs, 757-269-7263, firstname.lastname@example.orgFor Further Reference:
For non-scientists: Proton's party pals may alter its internal structure
Jefferson Lab is managed and operated for the U.S. Department of Energy's Office of Science by Jefferson Science Associates, LLC, a joint venture between Southeastern Universities Research Association, Inc. and CSC Applied Technologies, LLC.
Kandice Carter | EurekAlert!
A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne
Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology