Prestigious Physics Fellowship Supports Alumna’s Research
Date published: Aug. 12, 2020
Searching for Dark Matter
In a mountain range in Italy, Sophia Andaloro, BS ’19, investigates dark matter —
a big, unexplained mass found all over the universe that interacts gravitationally
with atoms but is invisible.
From looking through telescopes, scientists have determined that about five times
more dark matter exists than visible matter such as protons, electrons, planets and
stars. The dark matter doesn’t engage with light in a way that creates visible charge
that can be seen, so scientists are unsure about its nature. Nonetheless, scientists
study dark matter from two sides: theoretical and experimental. Andaloro works on
the experimental side, so she is actively searching for dark matter in a lab. Theorists,
meanwhile, are trying to come up with viable candidates for what types of particles
or conglomerates of masses this dark matter could be.
“Dark matter was discovered more than 80 years ago, but it wasn’t until 20 years ago
that there was a push to explore it further and detectors sensitive enough to do so,
with the technologies that we use to detect it,” said Andaloro. “We know that it’s
something massive that interacts with gravitational force. Hopefully, we can see it
interact in some way with another force using detectors, and then we can try to infer
what it is; trying to get that really weak interaction that the theorists have told
us might be present is what we set up our detectors for.”
The Xenon Experiment in the Italian mountains uses an Earth-based detector; sometimes
experimental dark matter physicists like Andaloro send up satellites to look for dark
matter, but this particular experiment is one done from Earth.
“We set up really sensitive detectors with really pure material and monitor them for
months to years, looking for possible interactions; all of that monitoring and setting
up sensors to try to catch interactions takes such high computing power that it really
is this last generation of physics experiments that made searching for it directly
on Earth possible,” explained Andaloro.
Employing Fellowships, Stewarding Science
One of the 2019 Cardinal Spellman recipients at UD, Andaloro received both the 2020
NSF Graduate Fellowship and the Department of Energy National Nuclear Security Administration
Stewardship Science Graduate Fellowship (DOE NNSA SSGF) this past year, her first
year in graduate school at Rice University. She is one of five graduate students working
in a range of physics fields, as well as materials science, who will join the NNSA
program this fall.
The DOE NNSA established this program in 2006 to meet a demand for scientists with
deep training in areas of interest to stewardship science and to support the education
of doctoral students researching high energy density physics, nuclear science, materials
under extreme conditions and hydrodynamics. Stewardship science is concerned with
the collection and reporting of monitoring data in an ecosystem to inform management
of a natural resource. The DOE NNSA’s Fiscal Year 2020 Stockpile Stewardship and Management Plan (SSMP) aims “to ensure the safety, security and effectiveness of the U.S. nuclear weapons
stockpile and to maintain the scientific and engineering tools, capabilities and infrastructure
that underpin the nuclear security enterprise.”
The NSF Graduate Fellowship wouldn’t have changed Andaloro’s path, but the NNSA will,
as it is geared toward the stewardship missions of the NNSA. This fellowship in particular
looks at the pillars of the “stewardship of science” mission, which encompass understanding
how our nuclear stockpiles can be safely monitored; this monitoring includes not only
U.S. stockpiles but also those on a global level in an attempt to keep everything
in check. Nuclear disarmament is a side mission related to Andaloro’s research, and
the fellowship’s focus on nuclear monitoring also fits into the understanding of xenon
as a nuclear detector material.
“What we have is a big vat of xenon that is sensitive enough to potentially detect
dark matter, so I would be trying to take the knowledge and science from that and
apply it to using the xenon in a nuclear security capacity,” she said. “You get so
much information out of the technologies that my collaboration builds, so it would
be a shame if we didn’t utilize all of that technology in stewardship science as well.
The motivation, then, is bringing everything that the dark matter experiments and
communities have built up in the past 20 years into stewardship science, and that
was my proposed plan for the fellowship.”
For the most part, over the next four years while she has the fellowship, she’ll be
continuing to work on the Xenon Experiment, because this experiment is very closely
tied to her project for the fellowship. The main difference from the NSF is that she
will have to do a summer practicum at a national laboratory, spending a summer as
a fellow for 12 weeks and working on a project at one of the sites, which could change
the course of her thesis slightly, but she intends for her topic to stay in the realm
of data science and the heavy analysis of dark matter detectors.
“The practicum at the lab is one reason I chose the NNSA over waiting to hear if I’d
gotten the NSF,” she said.
In the Gran Sasso mountains, the Xenon Experiment uses very cold, very pure liquid
xenon, isolating it and setting up shields (being under a mountain is crucial for
this). Detectors or sensors are all around the xenon, and Andaloro and the other scientists
look for a particle that comes in and scatters off of some part of the xenon; it could
scatter off of the electrons or the nucleus, for example. Andaloro is particularly
interested in the difference between scattering off of electrons and scattering off
of the nucleus; the traditional dark matter particle that paved the way for this experiment
is the Weakly Interacting Massive Particle (WIMP), which would theoretically interact
with the nucleus, but lately there have been other candidates, such as axions, which
would theoretically interact better with the electrons in the xenon, so it’s important
to isolate the nuclear from the electric recoils.
“Originally we thought that if a particle is interacting with the electrons, then
it’s coming from backgrounds — radiation, gamma rays, stuff like that — because these
types of backgrounds really like electrons,” said Andaloro. “We were isolating the
nuclear signals from the electronic signals because we wanted to examine the nuclear
recoils for dark matter. Then, in June, the XENON experiment reported an excess of low-energy electronic recoils, which we report could come from a few things. This could be a typical background
source like unaccounted-for tritium (a type of hydrogen isotope), could be caused
by the magnetic moment of the neutrino (the lightest standard model particles we know
of), which would be a significant discovery, or thirdly, could be caused by axions,
a dark matter candidate. Further testing on these electronic recoils in XENONnT will
in part rely on my contributions to our backgrounds characterization.”
The fellowship is extendable for four years, and Andaloro’s doctoral program, of which
she is now in her second year, will take five years, so they will expire around the
“So for the next four years, I’ll be working on this,” she said.
Furthering Her Physics Career
As Andaloro explained, there are basically three paths for physics doctoral students.
They can go into academics, work in a national lab, or go into industry. Andaloro
has been a TA frequently and does like teaching (she especially loved teaching at
UD), but she is wary of the intensely competitive nature of academics and also doesn’t
like that you don’t have much say in where you end up.
“I would like to have the freedom to move around, geographically as well as in research
project areas,” she said.
Her practicum at the national lab could determine her career path, but she also finds
industry very intriguing.
“There is a lot of give-and-take between industry and academic research,” she said.
“Usually industry takes more from academia than it gives, but one interesting example
of it being the other way around is how academia took the vessel for a detector material
from an industrial company that builds cargo ships. I like that type of connection,
and it would be fulfilling to figure out how to apply what I learn in particle physics
in the next four to five years to a more industrial problem.”
Ultimately, there are pros and cons to all paths, and she will determine over these
next years what she is most suited for.
Andaloro came to UD because her older sister is also an alumna, who graduated the
May before Andaloro arrived, and Andaloro had also participated in the Arete summer program on campus, so she was already familiar with the university.
“I came in as a math major,” she said. “I knew Dr. Andrews and thought he was awesome — I thought, wow, this is a really cool department; I
hadn’t realized math could be so personable and fun and friendly. I came to UD because
I knew I would find fulfillment through the close relationships with teachers as well
as the community; I knew my sister had had so much personal, spiritual growth there
While UD’s Physics Department is small and doesn’t provide as many internal research
opportunities as at larger schools, Andaloro believes it to be outstanding.
“Especially in the past five or so years, the faculty is amazing, and the research
opportunities are growing,” she said. “Dr. Flanagan is a particle physicist, and Dr. Hicks was my mentor; she’s been so supportive. Really, everyone in the department is outstanding;
you don’t get that type of department at most universities. To have all of the faculty be amazing is really hard to come by.
“Also, at UD there are no TAs; you know the professors by name,” she added. “It was
a little shocking coming to Rice because even though it’s also a relatively small
school, you don’t have that relationship with your professors. I love that the professors
at UD are committed to the students; that comes first over research, publications,
grants. I’m glad I went to UD because it has such great faculty. I don’t think I’d
have been a physics major, or at least a successful physics major, without them.
“At UD, it’s amazing how many lives they change with so little resources,” she concluded.
“I hope UD keeps getting more physics students, because I know we’re out there; so
many of my friends are doing amazing things, so hopefully word about them spreads,
and we get the word out about the Physics Department.”
Discover more about UD’s Physics Department.