The nucleus—coming soon in 3-D

March 5, 2018, US Department of Energy
The Radial Time Projection Chamber, shown installed in Jefferson Lab's Experimental Hall B, was built to measure the nuclei of helium-4 in the experiment. This measurement demonstrates that 3-D imaging of the inner structure of the nucleus is now possible. Credit: US Department of Energy

Physicians have long used CT scans to get 3-D imagery of the inner workings of the human body. Now, physicists are working toward getting their first CT scans of the inner workings of the nucleus. A measurement of quarks in helium nuclei demonstrates that 3-D imaging of the inner structure of the nucleus is now possible.

Nathan Baltzell is a postdoctoral researcher at the Department of Energy's Thomas Jefferson National Accelerator Facility in Newport News, Va. He says this successful measurement is one of the first steps toward imaging nuclei in a new way.

"It's a proof-of-principle measurement that opens up a new field – imaging nuclear structure in three dimensions with GPD tomography," he says.

He explains that GPDs, or generalized parton distributions, provide a framework that, when combined with experimental results, allows nuclear physicists to complete a 3-D rendering of the building blocks of subatomic particles, such as the proton, neutron, and now, even the nucleus.

GPDs are already being applied to 3-D imaging studies of protons and neutrons at Jefferson Lab. These studies are helping researchers understand how quarks and gluons build protons and neutrons. Now, Baltzell and his colleagues want to open a new window into the structure of the nucleus by extending this GPD tomography technique to nuclei.

"We've done these kinds of studies of quarks and gluons inside protons and neutrons for quite a while," he says. "But in a nucleus, where you have multiple neutrons and protons together… We don't quite know how the behaviors of quarks and gluons change and how they move together differently when you put them in a nucleus."

The experiment was conducted in 2009 at Jefferson Lab's Continuous Electron Beam Accelerator Facility, a DOE Office of Science User Facility. In it, electrons were beamed into the nuclei of helium-4 atoms.

"We started with helium-4 as our proof of principle for this study," Baltzell says. "We chose helium-4 because it is a light nucleus, relatively dense, and spinless. These characteristics make it experimentally attractive and the theoretical interpretation much simpler."

The experimenters were interested in the roughly 3,200 events they recorded of the electrons interacting with individual quarks inside the nuclei. For each of these events, the outgoing electron, the helium nucleus and a photon given off by the individual were all recorded.

"To make a precise measurement like this, you want to measure everything that comes out. This is the first time we measured all of the particles in the final state," Baltzell adds.

The result of the experiment was published last fall in Physical Review Letters.

Now that the researchers have shown that this technique is feasible, the collaboration is taking the next step to continue these studies with the new capabilities afforded by the upgraded accelerator and experimental equipment at Jefferson Lab. A new experiment has already been planned to begin the long process of actually composing that 3-D image of the internal quark-gluon structure of the helium-4 .

Explore further: New picture of atomic nucleus emerges

More information: M. Hattawy et al. First Exclusive Measurement of Deeply Virtual Compton Scattering off He4 : Toward the 3D Tomography of Nuclei, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.119.202004

Related Stories

New picture of atomic nucleus emerges

March 2, 2012

( -- When most of us think of an atom, we think of tiny electrons whizzing around a stationary, dense nucleus composed of protons and neutrons, collectively known as nucleons. A collaboration between the U.S. ...

CEBAF begins operations following upgrade completion

December 4, 2017

The world's most advanced particle accelerator for investigating the quark structure of matter is gearing up to begin its first experiments following official completion of an upgrade to triple its original design energy. ...

Wallflowers become extroverts in a crowd

September 28, 2010

While it's long been said that two's company and three's a crowd, that's just how mesons like it. A recent experiment at DOE's Jefferson Lab demonstrates that these subatomic particles engage more with other particles when ...

New method to better understand atomic nuclei

September 24, 2015

The precise structure of atomic nuclei is an old problem that has not been fully solved yet, and it also constitutes a current research focus in the field of natural sciences. Together with colleagues from Bonn University, ...

Proton's party pals may alter its internal structure

November 18, 2009

A recent experiment at the DOE's Thomas Jefferson National Accelerator Facility has found that a proton's nearest neighbors in the nucleus of the atom may modify the proton's internal structure.

Recommended for you

CMS gets first result using largest-ever LHC data sample

February 15, 2019

Just under three months after the final proton–proton collisions from the Large Hadron Collider (LHC)'s second run (Run 2), the CMS collaboration has submitted its first paper based on the full LHC dataset collected in ...

Gravitational waves will settle cosmic conundrum

February 14, 2019

Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.