The Axion Dark Matter research group focuses on searches for dark matter in the form of axions and axion-like particles (ALPs) both in astrophysical observations and dedicated laboratory experiments. It is supported by a CERN lighthouse initiative (DIRAC), by Denmark's Independent Research Fund (DFF), and previously by a Starting Grant from the European Research Council. The group is hosted at the Center for Cosmology and Particle Physics Phenomenology (CP3 Origins) University of Southern Denmark (SDU).
The nature of dark matter, which makes up more than 80% of the total matter in the Universe, is one of the most pressing questions in fundamental particle physics, astrophysics, and cosmology. Axions and ALPs are promising dark matter candidates which could produce specific observational signatures in astrophysical observations and in laboratory searches.
Please feel free to contact us for potential thesis projects! To get an idea, check out theses done by members of our group here.
(10/2026) This paper (led by Atreya with help from Dominik and Sara) combines observations from H.E.S.S. and Fermi to search for signatures of decaying dark matter axions. It's published in JCAP.
(09/2026) Manuel presented our first results of a cryogenic optical filter bench at the 2026 edition of the applied superconductivity conference in Pittsburgh, USA.
(07/2026) Congratulation to Dr. Sara Porras Bedmar who successfully defended her thesis with highest possible grade in the German University system! Her thesis is available here.
(06/2025) Our master students Dominik and Viktor (who Manuel co-supervised) both successfully defended their master theses - congrats to both!
(05/2026) Year's in the making: our comprehensive characterization paper of a transition edge sensor module is now available on arXiv and submitted to Physical Review Applied. The work has also been presented at the IDM 2026 conference.
(05/2026) Our CERN lighthouse initiative just had its kickoff meeting. We look forward to collaborate with our colleagues at CERN and in Denmark to advance particle physics. We will be supported with a PhD student.
Check out our news archive for older posts.
Joakim Rützou Rosenkilde
Transition Edge Sensor, ALPS II
SDU
Dominik Pastuszka Malek
H.E.S.S.
SDU
Farhana Khanom
SNSPDs
SDU
In this analysis, which was led by Atreya with support from Dominik and Sara, we use observations from the both H.E.S.S. and the Fermi LAT from multiple active galactic nuclei (AGNs) to search for signatures of decaying axions. If such particles make up all of the dark matter, they could - depending on their mass - sometimes decay into optical and infrared photons. These photons would contribute to cosmic radiation fields encountered by gamma rays originating from AGNs on their way to Earth. As a consequence we would expect a stronger attenuation of gamma rays. We did not find evidence for such an additional suppression leading to constraints on the axion life time. The paper is published in JCAP.
In this paper, we present a detailed characterization of our cryogenic single photon detector - a transition edge sensor. We show that we can observe almost 90% of all photons sent towards the detector. We develop new analysis methods for background rejection and for fitting the signal arriving at the detector making use of the full energy and timing information. Through a simulation study, we are able to show that our detector is very promising for rare-event searches in, e.g., ALPS II or axion interferometers. The preprint is available on arXiv and submitted to Physical Review Applied.
The universe is penetrated by a faint glimmer of light originating from all stars and dust in galaxies. This extragalactic background light (EBL) holds information about the number of stars formed throughout cosmic history as well as properties of interstellar dust. However, it is so dim that it is extremely hard to observe directly. In this paper, we present the first open-source code to model the EBL and show how we can constrain dust properties with gamma-ray observations. It's published in A&A and the code is available on GitHub.
Our paper (published in Scientific reports) explores whether deep neural networks can learn to tell the difference between real single-photon signals and random background noise in the time-trace output of our cryogenic transition edge sensor. What we found was surprising: despite careful optimization, the neural network couldn’t outdo traditional analysis methods at spotting real photon events, largely because background noise hides photon-like features that confuse the classifier. Our work highlights both the promise and the limits of applying AI to particle detection and points toward smarter algorithms that might one day help reveal new physics hiding in the noise. 
When an enormous explosion in the distant universe hurled gamma rays toward us in the record-breaking burst GRB 221009A, astronomers saw an opportunity to probe one of cosmic magnetism’s biggest mysteries: the strength of the magnetic field threading the seemingly empty space between galaxies. As gamma rays travel across the universe, they can spawn pairs of electrons and positrons that are bent by intergalactic magnetic fields, creating a delayed cascade of lower-energy gamma rays. By analyzing data from NASA’s Fermi Large Area Telescope and finding no significant delayed cascade, we set strong limits yet on how weak those intergalactic magnetic fields can be. The paper is published in PRD.
Detecting dark matter axions requires incredibly sensitive instruments. Our study now published in PRD shows how an open Fabry-Pérot resonator — essentially a precision “light echo chamber” operating at gigahertz frequencies and chilled to near-absolute zero — could boost our ability to spot the tiny electro-magnetic whispers axions might produce in a magnetic field. With clever engineering, this approach could probe axion interactions far beyond what traditional designs can reach, opening a promising new window on the dark side of the cosmos. 
Using the latest data compilation of measurements of the cosmological photon background from optical wavelengths to X-ray energies, we searched for a decay line signal from axion dark matter. We could derive new constraints that improve on previous results by roughly one order of magnitude. Also, we find that axion parameters that could explain an excess observed with the LORRI instrument on the New Horizons probe are in tension with other experiments. The paper is submitted to PRD and available on arXiv.
Even the tiniest background light from ordinary black-body radiation can mimic the signal we are looking for with our transition edge sensor. This paper from the ALPS II TES team and published in PRD dives into the heart of that problem by combining detailed simulations with real measurements of how thermal radiation sneaks into our TES. We show that the unwanted background seen in their setup matches what you’d expect from black-body radiation and that improving the energy resolution of the sensor can cut this noise by an order of magnitude.
We re-analyzed gamma-ray data from certain distant galaxies taken with the H.E.S.S. and Fermi telescopes to search for extended gamma-ray emission around these sources. Usually, we believe that these sources could be pointlike, but gamma-ray induced particle cascades could lead to a halo around them. The size of the halo depends on the strength of intergalactic magnetic fields. We didn't see any sign of extended emission, which leads to new strong constraints on the magnetic field strength. Our findings our published in the Astrophysical Journal Letters and also available here.
For the first time, we have applied machine learning to data of our transition edge sensor in order to improve the rejection of unwanted background counts. As it turns out, approaches using neural networks outperform our previous analysis methods and suggest that we can efficiently suppress our dark current levels. Check out the full paper published in Annals of Physics or on the arXiv.
We used Fermi-LAT observations of bright gamma-ray outbursts of flat spectrum radio quasars (FSRQs) to search for oscillations between photons and axion-like particles. For the first time, we self-consistently include photon-photon dispersion off the radiation fields in these environments and let the magnetic field free to vary in our fitting. For the first time we are able to constrain the ALP photon coupling for ALP masses up to 200 neV with gamma-ray observations. The paper is published in PRD and available here.
In the presence of dense photon fields in the vicinity of gamma-ray production sites in the jets of active galactic nuclei, the conversion of photons into axion-like particles competes with photon-photon interactions such as dispersion and photon absorption. In our recent study, which is accepted in PRD (and available on the arxiv) we show that both effects are important to include when searching for ALP signatures in the spectra of these sources.
We estimate the sensitivity of the low energy technique of the LAT to detect a gamma-ray burst caused by the conversion of axion-like particles produced in extragalactic core collapse supernovae. We find that we could detect such a burst from supernovae in galaxies up to 10 Mpc (~30 million light years) away. The study is accepted for publication in PRD and available as a preprint on arxiv.
We have identified 15 core collapse supernovae observed with the Zwicky Transient facility (ZTF) that are potentially well suited to search for a gamma-ray burst signal produced from axion-like particles. With the continued operation of ZTF and the upcoming Rubin Observatory, this sample will grow significantly in the near future. Check out the proceedings article for the ICRC2021 on arxiv and our original study published in 2020 in PRL.
An open-source python package that calculates the conversion probability between gamma rays and axions/ALPs in various astrophysical magnetic-field environments. Check out the documentation here and the proceedings article for the ICRC 2021.
Using realistic simulations of future observations with CTA of active galactic nuclei, we present the sensitivity of CTA to detect signatures of axions and ALPs, to constrain the extragalactic background light, detect intergalactic magnetic fields, and search for Lorentz Invariance Violation. The paper is accepted in JCAP and you can find the preprint here.
Together with Jamie Davies from Oxford, we have put out a paper about the oscillations of photons into axion-like particles in the magnetic fields of jets of active galaxies. It turns out that the exact morphology of the magnetic field in the jet can be quite important - we need multiwavelength data to constrain it. Check out the paper published in PRD here.
The Axion - ALP - DM research group is supported by DFF and an ERC starting grant and hosted by the University of Southern Denmark
© Copyright 2026 Manuel Meyer - Image credits: Morten Mossin Madsen, Mohammadpour Mir, Scicom-Lab / DESY, Manuel Meyer
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