Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Zooming in on a proton packed with surprises

05.12.2003


The structure of the proton is under the microscope at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia, where a series of experiments continues to produce unexpected results.


The shape of the proton can differ, depending on the angular momentum of quarks.
(Gerald A. Miller/University of Washington)



Simple theories of proton structure say that the way electric charge is distributed in the proton is the same as the magnetization distribution. But Jefferson Lab results indicate these distributions are definitely different.

A fundamental goal of nuclear physics is to understand the structure and behavior of strongly interacting matter in terms of its building blocks, quarks and gluons. An important step toward this goal is a description of the internal structure for the proton and neutron, collectively known as nucleons. Jefferson Lab was built, in part, to study the physics of quarks and gluons and their connection to larger composite objects like protons.


The proton is the positively charged core of the hydrogen atom, the most abundant element in the universe. It is made up of three charged quarks and the gluons that bind them together. The quarks move around, so the proton has a charge distributed over its size. This leads to the generation of an electric current, which in turn induces a magnetic field. In addition, quarks and gluons both have spin, leading to a magnetic moment. The combination of the total magnetic field and the magnetic moment is a quantity called magnetization.

Jefferson Lab is uniquely positioned to measure the proton’s electric charge and magnetization distributions, the so-called electromagnetic form factors that describe its internal structure.

In two recent Jefferson Lab experiments, researchers directed the accelerator’s polarized electron beam toward liquid hydrogen cooled to 17 Kelvin (–429°F). Each electron in the beam has an intrinsic angular momentum, or spin. The beam of electrons is said to be "polarized" if their spins point — on average — in a specific direction. As an electron collided with a proton in the hydrogen target, the proton recoiled, becoming polarized during the interaction. The scattered electron and recoiling proton were then detected in two high-resolution spectrometers (HRS), and the proton polarization was measured by a specially developed detector called a proton polarimeter.

From these measurements, the researchers could obtain a ratio of electric charge distribution to magnetization distribution — the electric and magnetic form factors — at various depths inside the proton. Their experiments revealed unexpected and significantly different energy-dependence for the form factors. The data showed that the proton’s charge distribution is not the same as its magnetization distribution; the charge distribution is more spread out than the magnetization.

These results are very interesting to both experimental and theoretical physicists. The Jefferson Lab data has already had an impact on theoretical models, helping rule out some models, directing others toward a better description of internal proton structure.

One such model was developed in 1996 by physicists Gerald A. Miller and Michael R. Frank, both from the University of Washington in Seattle, and Byron K. Jennings from TRIUMF in Vancouver. The researchers predicted a fall-off in the ratio of the electromagnetic form factors but, at the time, they didn’t realize that experimental confirmation was possible. When the results of the first Jefferson Lab experiments probing proton structure were announced in 2000, the prediction was confirmed.

An interesting by-product of Miller’s theory is that the proton is not necessarily spherical in shape. Depending on the angular momentum of the quarks, the proton could be spherical in shape or more like a doughnut, a pretzel or a peanut. Miller says the variety of shapes is nearly limitless, and depends on the momentum of the quarks and the angle between the spin of the quark and the spin of the proton.

Media contact: Linda Ware, Jefferson Lab Public Affairs Manager, 757-268-7689, ware@jlab.org
Technical contacts: Vina Punjabi (punjabi@jlab.org); Charles Perdrisat (perdrisa@jlab.org)

Linda Ware | Jefferson Lab
Further information:
http://www.jlab.org/div_dept/dir_off/public_affairs/news_releases/2003/03protonshape.html

More articles from Physics and Astronomy:

nachricht Innovative LED High Power Light Source for UV
22.06.2017 | Omicron - Laserage Laserprodukte GmbH

nachricht Spin liquids − back to the roots
22.06.2017 | Universität Augsburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate satellite: Tracking methane with robust laser technology

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...

Im Focus: How protons move through a fuel cell

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...

Im Focus: A unique data centre for cosmological simulations

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...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

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)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>