CP violation with atmospheric neutrinos
Sub-GeV atmospheric neutrinos give Hyper-K and DUNE a measurement of the CP-violating phase that is independent of accelerator systematics.
Preprint, 2026 · arXiv:2605.16721
Stephan A. Meighen-Berger
Postdoctoral Research Fellow in Neutrino Phenomenology
University of Iowa, Department of Physics and Astronomy
I find the measurements next-generation neutrino detectors weren't designed for, and show they can make them. These range from leptonic CP violation with atmospheric neutrinos to new probes of dark matter. Having worked inside IceCube, P-ONE and Borexino, I build the transport and simulation tools that make these predictions hold up at the detector level.
Highlights
$\nu_\tau$ appearance in JUNO
A new neutral-current signature lets JUNO observe atmospheric $\nu_\tau$ appearance at 5$\sigma$, at energies no other experiment reaches.
Phys. Rev. D, 2024 · arXiv:2311.01667
Dark matter from cosmic-ray accelerators
The existence of ultrahigh-energy cosmic rays constrains dark matter-proton scattering, probing sub-GeV masses that direct detection cannot reach.
Phys. Rev. D, 2026 · arXiv:2512.18093
Prometheus, open neutrino-telescope simulation
The first public end-to-end simulation for neutrino telescopes in ice and water, now a community baseline.
Comput. Phys. Commun., 2024 · arXiv:2304.14526
Latest
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Where do neutrino telescope effective areas come from?
Neutrino telescopes see neutrinos through muons born kilometers outside the detector, and how far those muons travel sets how many neutrinos a telescope can catch. I compute that range analytically, including the random way muons lose energy. With two numbers per detector, the result matches the published effective areas of IceCube, KM3NeT/ARCA and P-ONE to about 1%. The calculation is available as the open Python package softpaws 1.0.
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Cosmic neutrino sources as particle colliders
Cosmic accelerators reach collision energies far beyond any machine on Earth, and the neutrinos they emit carry information about those collisions. With Carlos Argüelles and colleagues, we fix every astrophysical ingredient of a source from light observations, so that the proton collision cross section is the only unknown left. Applied to IceCube's neutrino sources and the record-energy KM3NeT event, this bounds collisions at energies up to about $10^5$ GeV, some well beyond the LHC. My part was computing how $pp$ and $p\gamma$ collisions produce neutrinos.
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Stars near the Milky Way's black hole as dark matter detectors
A few stars orbit the black hole at the center of our Galaxy on very tight paths, and if dark matter piles up there, they plunge through it on every orbit. With colleagues, we compute how much energy dark matter would exchange with such a star, using S4714 as an example. For a dense dark matter spike, this energy can match the star's own luminosity for interaction strengths that popular production scenarios predict. That makes the Galactic Center a natural laboratory for dark matter, complementary to detectors on Earth.
Research
Recent papers
- Estimating High-Energy Neutrino Effective Areas from Muon Propagation Wrote the paperDeveloped the idea
- Astrophysical Neutrino Sources as Colliders Developed the production of neutrinos from $pp$ and $p\gamma$ interactions
- Dark matter energy exchange in stars orbiting supermassive black holes Co-wrote the paperDeveloped the idea
- Towards Measuring the CP-Violating Phase with Atmospheric Neutrinos Co-wrote the paperDeveloped the ideaMentored student
Recent talks
- University of Iowa, Iowa City, USA, 2026. Probing Dark Matter Interactions Near Supermassive Black Holes
- Queen's University, Kingston, Canada, 2026. Probing Dark Matter Interactions Near Supermassive Black Holes
- Mitchell Conference, College Station, USA, 2026. Towards Measuring CP Violation with Atmospheric Neutrinos
- Stanford University, Stanford, USA, 2026. Towards Measuring CP Violation with Atmospheric Neutrinos