Second Time’s a Charm for Repeat Winners of JSA Fellowship

  • Three valence quarks trade gluons as pairs of sea quarks pop into and out of existence.

William & Mary’s Felipe Ortega-Gama and Duke University’s Andrew Smith are investigating the fundamental particles that comprise us

NEWPORT NEWS, VA – Grasping the fundamentals of nuclear physics is no small feat, but that’s exactly what two repeat Jefferson Science Associates, LLC, (JSA) graduate fellows are attempting to do. The JSA Graduate Fellowship program stipends are allowing the awardees to pursue advanced studies at their universities while also conducting research at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility.

Both are graduate students who are working on their Ph.D.s in nuclear physics. Felipe Ortega-Gama and Andrew Smith both feel honored to have been selected as fellows two years in a row. They were awarded the fellowship based on their high quality research proposals, academic standing and references.

Identifying the Electromagnetic Radius of Hadrons

As an undergraduate, Ortega-Gama was an intern for Raul Briceno at Jefferson Lab. It’s to Briceno that Ortega-Gama attributes much of his current success.  

“It’s all thanks to him that I’m here!” he says.

Following the conclusion of that internship, he obtained his master’s degree from the University of Waterloo in a joint program with the Perimeter Institute.

Now, Ortega-Gama is pursuing his Ph.D. at William & Mary. His faculty advisor is Jozef Dudek, who he feels privileged to work with. Additionally, he is in the Hadron Spectrum Collaboration at Jefferson Lab with Briceno. As he enters his second year as a JSA graduate fellow, he said he plans to continue his recent studies.

“I’m honored that Jefferson Lab is trusting me with more funding to continue on my chosen research path,” he says.

Throughout his fellowship with JSA, Ortega-Gama has been developing a way to effectively describe, from the fundamental level, the simplest nuclei, such as the single proton at the heart of a hydrogen atom. He is also working toward a better understanding of the interaction of protons and neutrons that are riffling with extra energy in so-called excited states.

A key aspect of this project is the study of the electromagnetic radius of hadrons – which include protons and neutrons -- and how the particles that comprise them, quarks and gluons, affect the size of their radius.

“This is central to understanding how the dynamics arise in such a way that specific particles are bound together,” he explains.

In his first year of funding, he devised a formal technique that was published in Physical Review D. The technique uses supercomputers to calculate the fundamental theory.

“The paper addresses what transition rates look like related to hadrons, restrictions on them, and how from these rates I am able to describe properties of excited states from first principles,” he says.

Ortega-Gama’s formal technique requires supercomputer calculations that approximate the fundamental theory. His research works to relate the physical observations made in experiments to the numerical results he gets from his calculations.

Now that he has secured a second year of funding, Ortega-Gama aims to finalize the computational effort and focus on better relating the theory to physical observables.

He says that he is eager to travel to conferences to share his results with other groups. He specifically hopes to attend the next Lattice Conference, as he was not able to in his first fellowship year due to COVID-19. In the future, he plans to finish his Ph.D., continue publishing and doing research in a postdoctoral position, and eventually secure a faculty position as a full-time professor.

Measuring the Lifetime of the Eta Meson

Andrew Smith is striving to earn his Ph.D. from Duke University. With Haiyan Gao as his faculty advisor, Smith is a part of the Gluex Collaboration in Hall D at Jefferson Lab. Within this collaboration, he is avidly working on the Primakoff Experiment, or PrimEX-eta experiment, that attempts to measure the lifetime of the eta meson.

He partners with two Jefferson Lab scientists, Tyler Hague and Igal Jaegle, who have contributed greatly to the project and who he praises for their ability to “bounce ideas off of each other.”

Their experiments are conducted by shooting photons at a liquid helium target, contained within a glass cell, to create an eta meson. An eta meson is a specific type of meson that is exceedingly short lived. Almost instantly after the eta meson is created, it decays into two photons. The photons are captured and measured by a detector.

“We can then reconstruct what they initially were, that being an eta meson or another type of meson, based on their measured momentum,” he said.

Based on where the photons strike the detector material, researchers can then gather information on eta mesons.

“We can reconstruct the angle of the initial particle to quantify how many eta mesons are measured as a function of the production angle,” Smith explained.

Smith and his team will determine the differential cross section of eta meson photoproduction, so they can, in turn, extract the decay width. The decay width is directly proportional to the Primakoff cross section – which is the dominant production mechanism for eta mesons at forward angles.

In his first year of funding, Smith worked on measuring the total Compton scattering cross section for the PrimEx-Eta experiment. The Compton scattering cross section is a measurement of the photons that scatter off the atomic electrons in the liquid helium target. This measurement will be used to validate the overall systematic uncertainties for the eta meson decay width measurement.

In his second year as a JSA fellow, Smith hopes to publish his first peer-reviewed research article.

“I will write a paper on the Compton measurements and get the preliminary measurements of the decay width of the eta meson,” he said.

As he continues in his career, he hopes to conduct more research in nuclear physics in a postdoctoral position and eventually secure a position as a staff scientist at a research institution.

JSA Graduate Fellowship Program

The SURA Board of Trustees first established the graduate fellowship program in 1989. The program, now supported by the JSA Initiatives Fund, contributes to each student’s research assistant stipend. All fellowship recipients attend universities that are members of SURA, a consortium of 60 leading research universities. Since the program’s inception, 244 fellowships have been awarded to students from 23 different SURA member universities. SURA built and operated Jefferson Lab, before becoming a partner of Jefferson Science Associates.

The full list of fellows participating in the 2021-22 program can be found here.

By Abbey Ballance

Contact: Kandice Carter, Jefferson Lab Communications Office, kcarter@jlab.org

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Jefferson Science Associates, LLC, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy's Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.