A journey from 10−15 cm to 1030 cm

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A neutrino produced near a distant accelerator may cross galaxies, stars, planets, and the Earth before leaving a faint pattern of light in Antarctic ice. My research uses that light to study the particle’s energy and direction, and the possible astrophysical environment in which it was produced.

Image: NASA, ESA, CSA, STScI (James Webb Space Telescope)

Dr. Lu Lu

Neutrino Hunter

Portrait of Lu Lu, experimental astroparticle physicist at the University of Wisconsin–Madison

The origins and acceleration mechanisms of the highest-energy particles in the Universe remain among the most enduring mysteries in modern physics. Studies of cosmic rays helped establish particle physics; today, we use the Earth’s atmosphere, Antarctic ice, and ocean water as components of vast detectors to probe this frontier. Do the laws of the Standard Model hold at extreme energies? Could these particles originate from dark matter or other new physics?

During my PhD at the University of Leeds (United Kingdom) and the University of Wuppertal (Germany), I searched for ultra-high-energy photons using data from the Pierre Auger Observatory. I then joined Chiba University (Japan) as a postdoctoral researcher, working on the IceCube Neutrino Observatory. I am grateful to my mentors: Alan Watson and Johannes Knapp in Leeds, Karl-Heinz Kampert in Wuppertal, and Shigeru Yoshida and Aya Ishihara in Chiba.

I lead a research group at WIPAC working across high-energy neutrino astrophysics, including real-time multimessenger observations, Galactic plane searches, diffuse flux measurements, and searches for the highest-energy neutrinos. My group focuses on analysis development, including simulation, reconstruction, and machine learning methods. I have also contributed to next-generation optical sensor development for IceCube-Gen2 and plan to extend this work in the future. My own contributions include the Glashow-resonance analysis, the TXS 0506+056 coincidence analysis, initiating the combined diffuse global fit and continued efforts, helping build the extremely-high-energy real-time alerts, the all-flavour Galactic neutrino analysis, and using AI methods to search for the highest-energy neutrinos.

Within the IceCube Collaboration, I previously served as co-lead of the Diffuse/Atmospheric Working Group and continue to serve on the Realtime Oversight Committee. My research is supported by external and institutional funding, including the NSF ACED award (as PI) and the WoU-MMA IceCube Data Analysis awards (as senior personnel; 2022–2025, 2025–2028), together with UW–Madison awards (Research Forward, the Ray MacDonald Award, and the Fall Research Competition), and has been recognized by the International Union of Pure and Applied Physics (IUPAP) Early Career Scientist Prize and the IceCube Impact Award for leading the ICEcuBEAR project.

Research Interests

Where are the highest energy particles from?

Photons

From X-ray and gamma-ray to UHE photons, they carry key information on the highest-energy sources. Difficulty: the Universe is opaque and leptonic sources dominate.

Neutrinos

Neutrinos are weakly interacting and ideal for astronomy. My prime interests are PeV astrophysical neutrinos and EeV cosmogenic neutrinos.

UHECR

A more than 100-year mystery. Charged particles bend in magnetic fields, making source identification difficult; mass composition remains uncertain.

Multi-Messenger

Combining photons, neutrinos, cosmic rays, and gravitational waves offers the most promising path toward identifying the first UHE sources.

Physics-Informed AI

Physics-informed machine learning and generative modeling of particle showers from the Earth’s atmosphere and Antarctic ice to collider experiments.

Selected Projects

A timeline of the main projects I have worked on since joining IceCube in 2015, from detector hardware in Japan to the Galactic plane in Madison.

2015

D-Egg: a dual-PMT optical module

A dual-PMT optical sensor for the next generation of IceCube, developed at Chiba University from design and simulation to laboratory validation.

2017 – 2021

The Glashow resonance

A particle shower detected at the Glashow-resonance energy, identified with a hybrid reconstruction combining electromagnetic and hadronic information.

2018

IceCube-170922A and TXS 0506+056

A high-energy IceCube alert observed in spatial and temporal coincidence with gamma-ray activity from the blazar TXS 0506+056.

2019

Extremely-high-energy alerts

The highest-energy component of IceCube’s real-time alert system, streaming candidate cosmic neutrinos to telescopes worldwide.

2019 – Now

Mapping the cosmic-neutrino spectrum

A global fit combining track- and shower-dominated IceCube samples under a common treatment of detector and atmospheric uncertainties. The results show evidence that the spectrum is not described by a single power law from 5 TeV to 10 PeV; updated analyses continue toward 10 PeV and beyond.

2022

Snowmass and multimessenger white papers

Community road maps for the field: high-energy and ultra-high-energy neutrinos in Snowmass, and the infrastructure for a collaborative multimessenger ecosystem. A CERN Courier feature surveys the detector concepts of the coming two decades.

2023

Idealised cascade reconstruction and IceCube-Gen2

Idealised reconstruction for cascades: the shower angular resolution achievable in IceCube-Gen2 and its implications for diffuse science.

2025

Interpreting the KM3NeT ultra-high-energy candidate

What the ultra-high-energy event candidate reported by KM3NeT implies: whether ultra-high-energy cosmic rays, neutrinos, and photons share a common origin, and how the IceCube and KM3NeT observations compare.

2026

Probabilistic particle-shower modeling

Mean shower descriptions extended to include event-by-event fluctuations and their energy dependence, validated against FLUKA simulations.

2026

Neutrinos from the Milky Way

The IceCube Multi-flavor Astrophysics Neutrino sample (ICEMAN): improved simulation, reconstruction, and event selection, establishing neutrino emission from the Galactic plane at 5.7σ.

Now

Joint IceCube–Auger searches

Searches for transient ultra-high-energy sources using IceCube neutrinos and photon candidates from the Pierre Auger Observatory.

Now

Energy flux and flavour composition of inner-Galaxy neutrinos

The energy flux and flavour composition of neutrinos from the inner Galaxy, following the Galactic-plane observation.

Now

Galactic PeVatron searches

The hunt for Galactic PeVatrons: sources with gamma-ray emission above 100 TeV, a full-sky map of all-flavour neutrinos, the Cygnus bubble, cut-off energy measurements of H.E.S.S. PeVatron candidates, and Galactic stacking analyses.

Now

All-flavour neutrino search beyond 10 PeV

Graph-neural-network and transformer selections for extremely high-energy events, extending IceCube’s reach across all neutrino flavours.

Now

Generative AI for particle showers

Generative models of particle showers in two and three dimensions, building on the probabilistic shower-modeling work.

A more complete record is on INSPIRE.

Group

Postdoctoral Researchers

  • Marco Muzio — Diffuse global fits, ultra-high-energy neutrinos, and multimessenger interpretation.
  • Wei Tian — Neutrino flavour composition and Galactic-center studies.
  • Yuhua Yao — Neutrinos from the Cygnus region, microquasars, and Galactic sources.

Alumni

  • Pierpaolo Savina — Postdoctoral researcher working on ultra-high-energy photons and multi-flavour neutrino searches; now at the Gran Sasso Science Institute.

Ph.D. Students

  • Zoë Rechav — Integrating partially contained cascades into diffuse astrophysical measurements using deep neural networks; maintaining the NNMFit diffuse fitting framework.
  • Emre Yildizci — Next-generation diffuse neutrino global-fit targeting 10 PeV and beyond; particle shower parameterisations with FLUKA.
  • Maxwell Nakos — Applying Graph Neural Networks to southern sky neutrino searches and extending them beyond 100 PeV, plus exploring transient ultra-high-energy sources with photon candidates detected by the Pierre Auger Observatory; generative AI particle-shower learning (CORSIKA 8 shower productions in air and ice).
  • Matthias Thiesmeyer — All-flavour neutrino searches focused on the Galactic plane and Cygnus bubble; generative AI particle-shower muon-map validation and application for the inner-Galactic neutrino flux measurement.
  • Leo Seen (co-advised with Prof. Ke Fang) — Correlating all-flavour neutrinos with >100 TeV photons detected by LHAASO; Galactic PeVatron searches.
  • Anirudh Sundara Rajan (co-advised with Prof. Yong Jae Lee, Computer Science) — Generative modeling for particle tracking.
  • Jesse Osborn (co-advised with Prof. Albrecht Karle) — Starting-track alerts and segmented Galactic diffuse measurements in the combined fit.

Alumni

  • Vedant Basu (co-advised with Prof. Albrecht Karle) — Characterized the astrophysical diffuse spectrum using medium energy starting events (MESE); now a postdoctoral researcher at the University of Utah.

Master’s and Undergraduate Researchers

  • Qiannan Wang — Three-dimensional particle-shower modeling with generative methods.

Alumni

  • Ian Crawshaw — Parameterizing particle shower profiles.
  • Yash H. Alapuria — Differential energy-flux measurements from the Galactic center.
  • Siwei Wang — Parameterizing in-ice muon flux.
  • Carter Shulick — Developing analytic parameterizations for photon propagation in transparent mediums.
  • Wil Cram — Building a real-time neutrino alert website and developing augmented reality applications.
  • Karter Bell — Developing hardware electronics for IceCube-Gen2.
  • McCartney Evenson — Monitoring real-time alerts and analyzing neutrino self-correlations.
  • Kieran Hizon — 10–100 PeV neutrino reconstructions.
  • Calvin Sprouse (REU) — Energy reconstruction of 10 PeV neutrino candidate 190331A.
  • Patricia McMillin (REU) — Geometry optimization for IceCube-Gen2.
  • Alex Canales (REU) — GEANT4 simulations for detector figure-of-merit studies.
  • Sam Benda — Undergraduate researcher on GPU photon simulations for next-generation optical modules; now a graduate student at UW–Madison.

High School Research Interns

  • Isaac Hessman — Neutrino correlation studies with the Milky Way’s Galactic bubble shock front.

Alumni

  • Levi Eberly — Anomaly pattern detection in real-time alerts.
  • Collin Bovenmyer — Literature research on real-time neutrino counterparts in X-ray and gamma-ray.

Teaching

Course poster for Physics 107, Ideas of Modern Physics Course poster for Physics 406, Special Topics: Introduction to Particle Astrophysics

Public Engagement

ICEcuBEAR mobile augmented-reality visualization of an IceCube event
ICEcuBEAR. Look at an IceCube event from all angles using augmented reality on your phone. iOS · Android
Neutrino Globe visualization showing IceCube neutrinos passing through the Earth
Neutrino Globe. Real neutrino data going through the Earth.
HoloLens augmented-reality event viewer developed for IceCube
ICEcuBEAR HoloLens. An event viewer for augmented reality. Real 3D to use with Microsoft HoloLens.
Photograph of an aurora, part of a cosmic-ray photography collection
Photos of Cosmic Rays. Here are some photos of cosmic rays. Also: school and public visits, cloud chambers, and radiation demonstrations.

Games

Element Hunt a periodic table game Neutrino Oscillation a neutrino oscillation game Particle Collide a particle collider game

Videos: project video 1 · project video 2

Selected Talks