NEUTRINO PHYSICS
The Universe reaches us through different kinds of cosmic messengers. Light, or photons, allows us to observe objects across the electromagnetic spectrum, while cosmic rays, neutrinos, and gravitational waves provide complementary views. Cosmic rays carry information about energetic particles accelerated in distant sources; neutrinos let us probe regions opaque to photons; and gravitational waves allow us to observe the motion and mergers of massive compact objects.
At ultrahigh energies (UHE; 𝐸 ≥ 10^17 eV), neutrinos are expected to be produced through interactions of UHE cosmic rays (UHECR; 𝐸 ≥ 10^18 eV), either near the astrophysical objects that accelerate them or as they travel through the Universe. UHECRs have been observed at energies beyond 10^20 eV, yet we still do not know what produces them.
Cosmic rays are electrically charged and are deflected by magnetic fields on their journey to Earth, obscuring where they came from. High-energy photons can point back to their sources, but they can be absorbed as they travel through space. Neutrinos have the best of both worlds. They are electrically neutral and interact extremely weakly, allowing them to travel enormous distances while preserving information about where they were produced. This makes them powerful messengers for tracing the origin of the highest-energy particles in the Universe.
Their extreme energies and long journeys also make UHE neutrinos powerful probes of fundamental physics and physics beyond the Standard Model, including Lorentz invariance violation, non-standard neutrino interactions, and sterile neutrinos.
To explore this physics, we need data.
Credit: Mauricio Bustamante
When an UHE neutrino interacts in a dense material, such as the ice at the South Pole, it produces a shower of particles that generates a short burst of radio waves through the Askaryan effect. Experiments like the Askaryan Radio Array (ARA) search for these radio signals using antennas buried deep in natural ice sheets.
The ice is particularly well suited for this technique because radio waves can travel long distances through it before attenuating. This allows a relatively small number of antennas to monitor enormous volumes of ice, making radio detection a practical way to search for extremely rare UHE neutrinos.
Credit: ARA Collaboration
I have been a member of the ARA Collaboration since 2022, where my work has spanned neutrino searches, detector operations, simulations, and directional reconstruction.
Diffuse Flux Search for UHE Neutrinos
My Ph.D. research culminated in ARA’s first full-array, full-livetime search for UHE neutrinos, combining more than a decade of data across all five ARA stations into the field's most sensitive search to date. I co-led this analysis, which significantly improves upon previous radio-neutrino constraints on the UHE neutrino flux and surpasses all other techniques at the highest energies.
See this conference proceeding. Final results under collaboration review.
Neutrino Directional Reconstruction:
Polarization Reconstruction and South Pole Ice Biaxial Birefringence
To determine the direction of incoming neutrinos, we rely on reconstructing the polarization of the radio signals they produce. I study polarization of calibration data and simulate effects of biaxial birefringence in South Pole ice affecting polarization measurements. Understanding this effect is essential to enable searches with directional reconstruction using in-ice detectors. In other words, this could open the door for complete astrophysics with the radio technique.
Biaxial birefringence is expected to rotate the polarization of signals as they travel through the ice, and this effect appears qualitatively consistent with calibration data. My colleague and I are currently expanding a model of biaxial birefringence to explain these observations and improving our polarization reconstruction techniques to incorporate these effects. This work is in preparation to perform a lower-threshold directional point-source search upon the finalized diffuse flux search.
Other work:
From 2023 to 2025, I served as co-lead for ARA detector operations, managing detector monitoring, performing calibration exercises, and supporting deployment preparations.
I've also done to studies of IceCube-ARA coincidence event rates, investigating the potential for an optical-radio coincidence search.
In addition, I'm part of the GENETIS project, a collaboration focused on using genetic algorithms to optimize detector and antenna layouts for enhanced sensitivity to UHE neutrinos.
