From The Department of Energy: “How Stiff Is the Proton?”

From The Department of Energy

Mohammad Ahmed
North Carolina Central University and Triangle Universities Nuclear Laboratory

Compton scattering setup at the High Intensity Gamma Ray Source. The central cylinder is the liquid hydrogen target. High energy gamma rays are scattered from the liquid hydrogen into eight large detectors that measure the gamma rays’ energy. Credit: Mohammad Ahmed, North Carolina Central University and Triangle Universities Nuclear Laboratory

The Science

The proton is a composite particle made up of fundamental building blocks of quarks and gluons. These components and their interactions determine the proton’s structure, including its electrical charges and currents. This structure deforms when exposed to external electric and magnetic (EM) fields, a phenomenon known as polarizability. The EM polarizabilities are a measure of the stiffness against the deformation induced by EM fields. By measuring the EM polarizabilities, scientists learn about the internal structure of the proton. This knowledge helps to validate scientific understanding of how nucleons (protons and neutrons) form by comparing the results to theoretical descriptions of gamma-ray scattering from nucleons. Scientists call this scattering process nucleon Compton scattering.

The Impact

When scientists examine the proton at a distance and scale where EM responses dominate, they can determine values of EM polarizabilities with high precision. To do so, they use the theoretical frame of Effective Field Theories (EFTs). The EFTs hold the promise of matching the description of the nucleon structure at low energies to the current theory of the strong nuclear force called quantum chromodynamics (QCD). In this research scientists validated EFTs using proton Compton scattering. This approach also validated the framework and methodology that underlie EFTs.


Proton Compton scattering is the process by which scientists scatter circularly or linearly polarized gamma rays from a hydrogen target (in this case, a liquid target), then measure the angular distribution of the scattered gamma rays. High-energy gamma rays carry strong enough EM fields that the response of the charges and currents in the nucleon becomes significant. In this study, scientists performed new measurements of Compton scattering from the proton at the High Intensity Gamma Ray Source (HIGS) at the Triangle Universities Nuclear Laboratory. This work provided a novel experimental approach for Compton scattering from the proton at low energies using polarized gamma rays. The study advances the need for new high-precision measurements at HIGS to improve the accuracy of proton and neutron polarizabilities determinations. These measurements validate the theories which link the low-energy description of nucleons to QCD.

Science paper:
Physical Review Letters

See the full article here.


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The The United States Department of Energy is a cabinet-level department of the United States Government concerned with the United States’ policies regarding energy and safety in handling nuclear material. Its responsibilities include the nation’s nuclear weapons program; nuclear reactor production for the United States Navy; energy conservation; energy-related research; radioactive waste disposal; and domestic energy production. It also directs research in genomics. the Human Genome Project originated in a DOE initiative. DOE sponsors more research in the physical sciences than any other U.S. federal agency, the majority of which is conducted through its system of National Laboratories. The agency is led by the United States Secretary of Energy, and its headquarters are located in Southwest Washington, D.C., on Independence Avenue in the James V. Forrestal Building, named for James Forrestal, as well as in Germantown, Maryland.

Formation and consolidation

In 1942, during World War II, the United States started the Manhattan Project, a project to develop the atomic bomb, under the eye of the U.S. Army Corps of Engineers. After the war in 1946, the Atomic Energy Commission (AEC) was created to control the future of the project. The Atomic Energy Act of 1946 also created the framework for the first National Laboratories. Among other nuclear projects, the AEC produced fabricated uranium fuel cores at locations such as Fernald Feed Materials Production Center in Cincinnati, Ohio. In 1974, the AEC gave way to the Nuclear Regulatory Commission, which was tasked with regulating the nuclear power industry and the Energy Research and Development Administration, which was tasked to manage the nuclear weapon; naval reactor; and energy development programs.

The 1973 oil crisis called attention to the need to consolidate energy policy. On August 4, 1977, President Jimmy Carter signed into law The Department of Energy Organization Act of 1977 (Pub.L. 95–91, 91 Stat. 565, enacted August 4, 1977), which created the Department of Energy. The new agency, which began operations on October 1, 1977, consolidated the Federal Energy Administration; the Energy Research and Development Administration; the Federal Power Commission; and programs of various other agencies. Former Secretary of Defense James Schlesinger, who served under Presidents Nixon and Ford during the Vietnam War, was appointed as the first secretary.

President Carter created the Department of Energy with the goal of promoting energy conservation and developing alternative sources of energy. He wanted to not be dependent on foreign oil and reduce the use of fossil fuels. With international energy’s future uncertain for America, Carter acted quickly to have the department come into action the first year of his presidency. This was an extremely important issue of the time as the oil crisis was causing shortages and inflation. With the Three-Mile Island disaster, Carter was able to intervene with the help of the department. Carter made switches within the Nuclear Regulatory Commission in this case to fix the management and procedures. This was possible as nuclear energy and weapons are responsibility of the Department of Energy.


On March 28, 2017, a supervisor in the Office of International Climate and Clean Energy asked staff to avoid the phrases “climate change,” “emissions reduction,” or “Paris Agreement” in written memos, briefings or other written communication. A DOE spokesperson denied that phrases had been banned.

In a May 2019 press release concerning natural gas exports from a Texas facility, the DOE used the term ‘freedom gas’ to refer to natural gas. The phrase originated from a speech made by Secretary Rick Perry in Brussels earlier that month. Washington Governor Jay Inslee decried the term “a joke”.


The Department of Energy operates a system of national laboratories and technical facilities for research and development, as follows:

Ames Laboratory
Argonne National Laboratory
Brookhaven National Laboratory
Fermi National Accelerator Laboratory
Idaho National Laboratory
Lawrence Berkeley National Laboratory
Lawrence Livermore National Laboratory
Los Alamos National Laboratory
National Energy Technology Laboratory
National Renewable Energy Laboratory
Oak Ridge National Laboratory
Pacific Northwest National Laboratory
Princeton Plasma Physics Laboratory
Sandia National Laboratories
Savannah River National Laboratory
SLAC National Accelerator Laboratory
Thomas Jefferson National Accelerator Facility

Other major DOE facilities include
Albany Research Center
Bannister Federal Complex
Bettis Atomic Power Laboratory – focuses on the design and development of nuclear power for the U.S. Navy
Kansas City Plant
Knolls Atomic Power Laboratory – operates for Naval Reactors Program Research under the DOE (not a National Laboratory)
National Petroleum Technology Office
Nevada Test Site
New Brunswick Laboratory
Office of River Protection
Radiological and Environmental Laboratory
Y-12 National Security Complex
Yucca Mountain nuclear waste repository

Pahute Mesa Airstrip – Nye County, Nevada, in supporting Nevada National Security Site