In 2010, Phiala Shanahan was an undergraduate on the College of Adelaide, wrapping up a level in computational physics, when she heard of an surprising discovery in particle physics. The information had nothing to do with any of the uncommon, unique particles that physicists had been trying to find on the time. Slightly, the revelation revolved across the mundane, ubiquitous proton.
That 12 months, scientists had measured the proton’s radius and found that the particle was ever so barely smaller than what earlier experiments had reported. This new measurement threw into query what physicists had assumed was well-understood: What precisely was the dimensions of the proton?
What would then be coined the “proton radius puzzle” instantly drew Shanahan’s curiosity, prompting a extra basic query: What else don’t we learn about this seemingly easy particle?
“Protons and neutrons make up 99 % of seen matter within the universe,” she says. “I assumed that, similar to the mass of the proton is thought very exactly, the dimensions could be too. That was one second pretty early on once I realized, there actually are basic questions that we nonetheless haven’t any solutions to.”
The proton puzzle was one impetus that propelled Shanahan to pursue theoretical particle and nuclear physics. Right now, she is the Class of 1957 Profession Growth Affiliate Professor of Physics at MIT, having not too long ago acquired tenure on the Institute.
In her analysis, she seeks a basic understanding of our bodily world. Utilizing the equations of the Normal Mannequin of Physics as her information, she is searching for basic bridges — concrete, mathematical connections between the habits of elementary particles, such because the quarks and gluons inside a single proton, and the interactions between a number of protons, which coalesce into the seen matter we see round us.
Tracing these basic connections will in the end assist physicists acknowledge breaks in our understanding, akin to cases when a proton interacts with darkish matter, which is assumed to make up 85 % of the full mass within the universe and for which the Normal Mannequin — our greatest illustration of our bodily understanding — has no clarification.
“We are attempting to know how one can bridge understanding from our most basic idea — this stunning predictive idea of basic particles — all the way in which as much as nuclear physics,” Shanahan says.
Up for a problem
Shanahan was born in Sydney, Australia, and spent most of her childhood and early training within the suburbs of Adelaide, the place she earned a scholarship to attend an all-girls college. She rapidly took to finding out math and science, studying new languages, and enjoying quite a lot of devices.
“On the time, I don’t suppose you can’ve picked me for a scientist relatively than a musician or a linguist,” she says.
After highschool, Shanahan stayed native, attending the College of Adelaide, the place she took courses in Latin and historic Greek, and performed in a canopy band on the weekends. She additionally pursued a bachelor’s diploma in high-performance computational physics, which she selected virtually as a private problem.
“It was the toughest diploma to get into on the time, and I assumed, ‘I need one thing difficult,’” she recollects.
Her curiosity in physics started to crystallize after listening to of the proton radius puzzle in the future in a analysis seminar. She additionally found that she loved analysis, after accepting a suggestion to work as a summer season assistant within the lab of her undergraduate advisor, Anthony Thomas, who specialised in nuclear physics. She continued working with Thomas by graduate college, additionally on the College of Adelaide, the place she earned a PhD in theoretical nuclear physics.
“I’d already been caught by this concept that we didn’t know almost as a lot concerning the proton as I assumed, so my PhD was about understanding in nice element the construction of the proton and what we might add to that understanding,” Shanahan says.
A direct hint
After ending her training in Australia, Shanahan appeared to take her subsequent step, exterior the nation. With funds from a touring fellowship, she deliberate out a two-month tour of physics departments and services throughout Europe and the US, together with at MIT. The expertise was a whirlwind, as Shanahan was launched at each cease to new concepts and avenues of analysis.
“The thoughts growth was actually thrilling,” she says.
When she got here residence to Australia, she discovered she was eager to maintain on the analysis monitor, and to stay overseas. Quickly, she packed her luggage for a postdoc place in MIT’s Division of Physics. She arrived on the Institute in 2015 and spent the following two years researching the interactions of gluons, the elementary, force-carrying particles that bind to quarks to type a proton.
“It’s very troublesome to measure experimentally sure points of the gluon construction of a proton,” Shanahan says. “I wished to see what we might calculate, which on the time was fairly a brand new factor.”
Till then, Shanahan thought of herself a principally “pen-and-paper” theorist. However she wished to see how far the habits of gluons — interactions referred to as quantum chromodynamics — might be immediately traced utilizing the equations of the Normal Mannequin. To take action would require large-scale numerical calculations, and she or he discovered herself studying a brand new set of computational instruments and exploring methods to seek for basic interactions amongst gluons utilizing machine studying — a novel method that Shanahan was one of many first to undertake, and which she continues to pursue immediately.
A artistic area
After ending her postdoc, she spent a 12 months as a college member on the School of William and Mary and as a senior workers scientist on the Thomas Jefferson Nationwide Accelerator Facility earlier than returning to MIT in 2018 as an assistant professor within the Heart for Theoretical Physics. Earlier than she put down campus roots, Shanahan spent the autumn semester on the Perimeter Institute for Theoretical Physics in Ontario, Canada, as a part of a fellowship that helps feminine physicists. This system offered meals and board for fellows, and likewise delivered meals to their places of work — all with the objective of liberating the physicists to concentrate on their work.
“That program actually gave me the launchpad for what grew to become my analysis agenda as a brand new college member,” she says. “It began from that quiet time the place I might truly suppose for hours at a time. That was extremely priceless, and it gave me the area to be artistic.”
At MIT, she continues to review the equations of the Normal Mannequin to know the quantum dynamics of gluons and quarks, and the construction of the proton, in addition to the interactions that underpin nuclear physics, and what the basic habits of sure nuclei can inform us concerning the situations of the early universe.
She can be specializing in nuclei which are utilized in darkish matter experiments, and is trying to map out the area of nuclear interactions that may be defined concretely by the Normal Mannequin. Any interactions exterior of this basically derived area might then be an indication of darkish matter or different phenomena past what the Normal Mannequin can clarify.
“Now my analysis group goes in all types of instructions,” she says. “We’re utilizing each device at our disposal, from pen-and-paper calculations, to designing and working new algorithms on supercomputers, to actually perceive new points of the construction and interactions of the matter that makes up our universe.”