What exactly is a sterile neutrino?

A sterile neutrino is a hypothetical type of neutrino that does not interact with ordinary matter; it would interact only with other neutrinos. This makes it very difficult to detect directly, hence the focus on indirect signs like oscillation patterns.

What does the SB&D detector do in this setup?

The SB&D detector measures the beam’s characteristics immediately after production, providing a baseline for what the beam should look like before any oscillations occur.

How do near and far detectors help identify anomalies in the neutrino beam?

By comparing measurements from the near detector and the far detector (Icarus), researchers can predict how many electron neutrinos should appear at the far location. An excess would indicate an anomaly potentially pointing to new physics like sterile neutrinos.

What is the liquid argon time projection chamber and why is purity important?

The LArTPC is the detector technology used because liquid argon reveals tracks and events clearly. Purity at the part-per-trillion level is crucial to maintain sharp imaging and accurate reconstruction of events.

When did the Icarus detectors move to CERN and get refurbished?

Two detectors were moved to CERN around 2015, were disassembled, refurbished, and updated with new components before being installed at Fermilab/CERN facilities.

When did Icarus start taking physics data and what’s next?

Icarus began its first physics run in July 2022 and completed four years of data collection, with additional runs planned together with newer detectors to continue the search for sterile neutrinos.

What is DUNE and how does it relate to Icarus?

DUNE is a long-baseline neutrino experiment that adopts the same technology and learns from the Icarus setup and other short-baseline detectors to improve near/far detector performance and image reconstruction, including AI-based methods.

ICARUS: The search for new physics

Fermilab

Science & Technology5 min read8 min video

Nov 18, 2025|20,458 views|1,299|100

Fermilab Physics

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TL;DR

ICARUS and DUNE: chasing sterile neutrinos with liquid-argon technology

Key Insights

Neutrinos come in flavors (electron, muon, tau) and oscillate between them as they travel, implying they have mass.

Sterile neutrinos are hypothetical particles that interact only with regular neutrinos, driving the search in short-baseline experiments.

The short-baseline program uses a near detector (SBND) and a far detector (ICARUS) on the same beam line to detect anomalies in neutrino flavor composition.

Liquid Argon Time Projection Chamber (LArTPC) technology enables precise tracking and the distinction between electron and photon showers, key for identifying neutrino interactions.

The Icarus project has a long, complex history of relocation, refurbishment, and commissioning, culminating in several years of stable operation and physics runs.

DUNE will extend these lessons to a 1,400 km baseline, leveraging AI-assisted image reconstruction and a broader program over the next decade to probe fundamental neutrino physics.

NEUTRINOS: A MYSTERIOUS YET ABUNDANT PARTNER OF MATTER

Neutrinos are among the universe's most abundant particles, passing through us in vast numbers every second. They come in three known flavors—electron, muon, and tau—and intriguingly, each flavor has a corresponding neutral partner. While neutrinos are electrically neutral, they do possess mass, a fact that emerged from observing flavor changes, or oscillations, as neutrinos travel from their production point to a detector. This oscillation means a neutrino created as one flavor can be detected later as a different flavor, revealing that flavor states mix and that mass eigenstates differ. The short-baseline neutrino program targets the possibility of additional, “sterile” neutrino types that would interact only with other neutrinos rather than with ordinary matter. The existence of sterile neutrinos would signal new physics beyond the established framework and could reshape our understanding of particle interactions and the universe’s evolution.

THE SHORT-BASELINE PROGRAM: NEAR AND FAR DETECTORS ON A SINGLE BEAM LINE

To test for sterile neutrinos, the program deploys two detectors located along the same neutrino beam: a near detector, SBND, and a far detector, ICARUS, with ICARUS positioned about 600 meters from the source. The near detector characterizes the beam immediately after production, establishing the expected composition and energy spectrum. By comparing the near detector measurements with what is seen at the far detector, researchers can predict how many electron-neutrinos should appear if there are no new physics effects. Anomalies—such as an excess or deficit of electron-neutrinos at the far site—could indicate oscillations into sterile neutrinos, signaling new physics beyond the standard three-flavor picture.

LIQUID ARGON TIME PROJECTION CHAMBER: A GAME-CHANGING DETECTOR TECH

ICARUS uses a liquid argon time projection chamber (LArTPC), a technology that provides exquisite 3D imaging of neutrino interactions. The purity of liquid argon is crucial because impurities degrade the delicate signals from ionization electrons. LArTPCs offer high-resolution tracking and the ability to distinguish electron-induced showers from photon-induced showers, which is essential for reducing background in neutrino oscillation studies. The detector’s design enables detailed reconstruction of interaction topologies, helping scientists identify the true flavors involved in each event. The combination of precise imaging and particle identification makes LArTPCs uniquely suited to long- and short-baseline neutrino research.

FROM GROSSE TO CERN: A RIGOROUS, MULTI-STAGE UPDRAFT OF ICARUS

ICARUS began as a pioneering detector in the Gran Sasso National Laboratory, with data collected between 2010 and 2013. Afterward, two separate detectors were moved to CERN around 2015, where they were disassembled, refurbished, and upgraded with new components. The move reflected a broader strategy: reuse proven detector technologies while enhancing performance for next-generation experiments. The transfer required careful reassembly, integration, and testing before installation resumed at the new site. This period culminated in commissioning, with systems fully prepared to observe neutrino interactions against a well-characterized beam.

THE COMMISSIONING AND FIRST LIGHT: YEARS OF BUILDING A STABLE BASELINE

Commissioning of the upgraded infrastructure progressed through 2017 and 2018, with final installations and preparations extending into 2019 and 2020. In August 2020, high voltage was turned on and the detector began recording tracks for the first time in its refurbished configuration. Since then, ICARUS has completed five years of continuous operation without a single glitch, a testament to the robustness of the infrastructure and the teams supporting it. This reliability laid the groundwork for sustained physics runs and a solid data set to test sterile neutrino hypotheses.

PHYSICS RUNS AND THE PATH AHEAD: LEARNING, RUNNING, AND EXPANDING

Icarus commenced its first physics run in July 2022, marking the start of a multi-year program of data collection and analysis. This phase spanned four years, with the expectation of an additional three years of data-taking that will combine observations from ICARUS with the newly operating near detector (referred to here as NEO) to sharpen sensitivity to sterile neutrino scenarios. The central goal remains: determine whether an external neutrino appearance or disappearance pattern can be attributed to sterile states, thereby confirming a new layer of fundamental physics.

DUNE: A LONG-BASELINE EXPERIMENT BUILT ON ICARUS LESSONS

DUNE—the Deep Underground Neutrino Experiment—delivers a conceptually similar approach but over a much longer baseline of about 1,400 kilometers. Using the same liquid-argon technology for both near and far detectors, DUNE is designed to push sensitivity to neutrino properties and potential new physics further than current experiments. The collaboration is leveraging lessons from ICARUS and SBND, including hardware improvements and advanced image reconstruction aided by AI. Over the next 10 to 15 years, DUNE aims to provide a comprehensive picture of neutrino behavior and the possibility of sterile states, contributing to a broader, worldwide program in particle physics.

THE BIG PICTURE: SCIENCE AS A PROGRESSIVE, SOCIETAL ENDEAVOR

Beyond the technical and scientific details, the ICARUS program embodies a broader view: the progress of science mirrors the progress of society. By solving intricate questions about neutrinos and seeking new physics, researchers contribute to our collective understanding of the universe and our place within it. The journey—from concept to detector to data analysis and eventual discovery—requires international collaboration, advanced technology, and patient, long-term commitment. The work at ICARUS and DUNE represents how scientific inquiry can drive innovation, inform other disciplines, and inspire future generations to pursue fundamental questions about the nature of reality.

Mentioned in This Episode

●Tools & Products

Common Questions

The Icarus detector is a liquid argon time projection chamber located about 600 meters from the neutrino source. It is part of the short-baseline neutrino program and is used to study neutrino types and search for anomalies that could indicate sterile neutrinos.

Topics

Short-baseline Liquid Argon Time Projection Chamber AI Image Reconstruction Argon Purity Near Detector Far Detector Long Baseline

Mentioned in this video

toolIcarus detector

Liquid argon time projection chamber detector located about 600 m from the neutrino source, part of the short-baseline neutrino program to search for sterile neutrinos.

toolSB&D detector

Detector that measures the characteristics of the beam immediately after production, establishing the near-beam baseline.

toolLiquid Argon Time Projection Chamber

The detector technology used (LArTPC) in Icarus; enables high-purity tracking and the ability to distinguish photon showers from electron showers.

toolDUNE (Deep Underground Neutrino Experiment)

Long-baseline neutrino experiment; uses similar technology and learns from Icarus and short-baseline detectors to improve near/far detectors and image reconstruction.

toolDUNE near detector

Near detector for the DUNE experiment, part of the near-far detector pair used for cross-checks with the far detector.