Monday, September 01, 2025

Doubling the gravitational-wave transient catalogue

The visualization shows binary black hole mergers with parameters consistent with the 86 events from the GWTC-4.0 catalog. The tracks of the black holes are shown in white, and the gravitational-wave emission is shown in colors ranging from purple to yellow. Dark purple colors represent comparatively weak gravitational waves, whereas yellow colors represent the strongest waves emitted near the merger. The strongest gravitational waves are emitted in the directions perpendicular to the instant orbital plane. For precessing systems, the orientation of their orbital plane is constantly changing. Credit: I. Markin (Potsdam University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), H. Pfeiffer (Max Planck Institute for Gravitational Physics)


LIGO-Virgo-KAGRA researchers at the Max Planck Institute for Gravitational Physics and at Leibniz University Hannover make significant contributions to detect and analyze new gravitational-wave candidates

The LIGO-Virgo-KAGRA (LVK) collaboration has today released new results from the first part of the fourth observing run (O4a), which took place from May 2023 to January 2024. The scientists discovered 128 new gravitational-wave (GW) signals in the data, all of which originated from mergers of black hole and neutron star - black hole binaries. Two of the signals were observed with unprecedented clarity. Alongside releasing the strain data, the researchers have published version 4.0 of the Gravitational Wave Transient Catalogue (GWTC-4.0), which contains lists of candidate signals and measurements of their properties. The collaboration is also publishing a set of papers to accompany the catalogue. These papers have been submitted to the Astrophysical Journal Letters for publication as a Focus Issue.

The Max Planck Institute for Gravitational Physics contributed to this success

Improvements in detector sensitivity and analysis techniques led to more detections than in previous observation runs. Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) and at Leibniz University Hannover, including many PhD students and postdoctoral researchers, have contributed to this achievement:
  • Researchers at the AEI provided the high-power pre-stabilized laser system for Advanced LIGO, and have developed and tested upgrades to the main laser source currently being used in the LIGO instruments.
  • The amplifier stage of the current laser sources in the Virgo and KAGRA instruments is based on developments and tests carried out by a collaboration between the AEI in Hannover and the Laser Zentrum Hannover.
  • AEI researchers have developed sophisticated waveform models that are used to distinguish real cosmic sources from random fluctuations and terrestrial disturbances that appear in the detector.
  • The waveform models used as templates to detect binary black holes and neutron-star—black-hole binaries were developed at the AEI. These state-of-the-art waveform models, augmented with spin-precession effects, are also employed for production runs on the signal candidates to infer their astrophysical and cosmological information.
  • Another waveform model, developed at the AEI, includes the effect of mode asymmetry and the resulting 'kick', and is used in the analysis.
  • Scientists at AEI have used signal candidates to search for deviations from general relativity.
  • Neural network-based parameter estimation methods developed at the AEI provide a rapid and accurate way to infer the properties of binary black hole mergers.
The scientists are presenting a detailed analysis of 86 of the new signals in the catalogue, 84 of them binary black hole mergers, 2 black-hole–neutron-star mergers. In addition, the researchers found a further 42 signals that are most likely to have been produced by astrophysical sources. In total, 218 gravitational-wave candidates have been detected so far – 90 from the first three observing runs and 128 new ones.



I. Markin (Potsdam University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), H. Pfeiffer (Max Planck Institute for Gravitational Physics


Media contacts:

Dr. Benjamin Knispel
Press Officer AEI Hannover
+49 511 762-19104
benjamin.knispel@aei.mpg.de

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
+49 331 567-7303
elke.mueller@aei.mpg.de

Scientific contacts:

Prof. Dr. Alessandra Buonanno
Director | LSC Principal Investigator
Tel: +49 331 567-7220
Fax: +49 331 567-7298
alessandra.buonanno@aei.mpg.de
Homepage of Alessandra Buonanno

Prof. Dr. Karsten Danzmann
Director | LSC Principal Investigator
Tel: +49 511 762-2356
Fax: +49 511 762-5861
karsten.danzmann@aei.mpg.de
Homepage of Karsten Danzmann

Dr. Frank Ohme
Research Group Leader | LSC Principal Investigator
Tel: +49 511 762-17171
Fax: +49 511 762-2784
frank.ohme@aei.mpg.de
Homepage of Frank Ohme

Dr. Héctor Estellés Estrella
Junior Scientist/Postdoc
Tel: +49 331 567-7193
hector.estelles@aei.mpg.de

Lorenzo Pompili
PhD Student
Tel: +49 331 567-7182
Fax: +49 331 567-7298
lorenzo.pompili@aei.mpg.de

Elise Sänger
PhD Student
elise.saenger@aei.mpg.de

Apl. Prof. Dr. Benno Willke
Group Leader
Tel: +49 511 762-2360
benno.willke@aei.mpg.de


Publications

1. The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration
GWTC-4.0: An Introduction to Version 4.0 of the Gravitational-Wave Transient Catalog
arXiv:2508.18080 (2025)
Source | DOI

2. The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration
GWTC-4.0: Methods for Identifying and Characterizing Gravitational-wave Transients
arXiv:2508.18081 (2025)
Source |  DOI

3. The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration
GWTC-4.0: Updating the Gravitational-Wave
Transient Catalog with Observations from the First Part of the Fourth
LIGO-Virgo-KAGRA Observing Run
arXiv:2508.18082 (2025)
Source |  DOI

4. The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration
GWTC-4.0: Population Properties of Merging Compact Binaries
arXiv:2508.18083 (2025)
Source | DOI

5. The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration
Open Data from LIGO, Virgo, and KAGRA through the First Part of the Fourth Observing Run
arXiv:2508.18079 (2025)
Source | DOI

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A new candidate for dark matter

When a superheavy, charged gravitino passes through the scintillator fluid, photons are produced that generate a characteristic “glow.” The detector should be able to detect this trace. © K. Beil, Formgeber/Milde Science Communication


Could traces of superheavy charged gravitinos be detected by underground detectors?

To the point:
  • Big mystery: The nature of dark matter remains unclear. Possible candidates are new types of elementary particles. The present work proposes superheavy charged gravitinos to explain dark matter. These particles differ radically from all previously proposed candidates (axions, WIMPs, etc.).
  • Possible detection: A research team involving the Max Planck Institute for Gravitational Physics and the University of Warsaw shows how new underground detectors could detect these particles based on their distinctive traces.
  • Interdisciplinary approach: The analysis combines two very different fields of research: elementary particle physics and the search for a fundamental theory using methods of modern quantum chemistry.
In an earlier study, Hermann Nicolai from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) at Potsdam Science Park and Krzysztof Meissner from the Faculty of Physics at the University of Warsaw had already postulated superheavy electrically charged gravitinos as possible candidates for dark matter and proposed methods to search for them in planned underground experiments. The recently published paper shows how large underground neutrino detectors could detect these particles based on their distinctive traces. In the paper, the researchers present a detailed analysis of the specific signatures that events caused by gravitinos could produce at the Jiangmen Underground Neutrino Observatory (JUNO) and in future liquid argon detectors such as the Deep Underground Neutrino Experiment (DUNE). The current analysis also sets new standards in terms of interdisciplinarity by combining two very different areas of research: elementary particle physics and the search for a fundamental theory on the one hand, and methods of modern quantum chemistry on the other. The latter were contributed to this collaboration by Adrianna Kruk and Michal Lesiuk from the Faculty of Chemistry at the University of Warsaw.

An unsolved mystery

The nature of dark matter remains one of the greatest mysteries of modern astrophysics. Numerous proposals are on the table, ranging from novel elementary particles to fundamental modifications of Einstein's theory of gravity. In particle physics, supersymmetric particles, ultralight axion-like particles, and the much heavier WIMPs (weakly interacting massive particles) are discussed as possible candidates, all of which interact only very weakly with normal matter. “Many researchers had high expectations for the results of the Large Hadron Collider experiments,” says Hermann Nicolai, Director Emeritus at the AEI, “but no new particles beyond the Standard Model were detected.” Other experiments have also failed to find any evidence of such particles in this 40-year search. Nor have proposed modifications to Einstein's theory led to satisfactory answers. However, with the possible direct detection of superheavy gravitinos in underground detectors, it may now be possible to track down dark matter with a new idea.

The proposal for a dedicated search for superheavy gravitinos is based on previous work on the unification of fundamental interactions by Nicolai and his colleague Krzysztof Meissner, which could explain in particular the fermion spectrum of the Standard Model of particle physics with three generations of quarks and leptons. In this model, superheavy gravitinos (which carry spin 3/2) would be the only new fermions beyond the Standard Model. These still hypothetical elementary particles differ significantly from all previously proposed candidates. For example, a gravitino carries fractional electric charge and, in principle, can be detected directly thanks to its interaction with normal matter. However, the search is made enormously difficult by its extremely low abundance (roughly estimated to be only one gravitino per 10,000 km3 on average), which is why there is no prospect of detection with currently available detectors. However, with the commissioning of new giant underground detectors, realistic possibilities for searching for these particles are now opening up.

Superheavy gravitinos in a neutrino detector

“The observation method we propose for superheavy gravitinos is not based on ionization, as one might expect, but on a kind of ‘glow’. This glow comes from photons that should be generated when such particles pass through the detection fluid in large neutrino observatories,” says Hermann Nicolai, co-author of the study. “According to our calculations, this glow can last from a few microseconds to several hundred microseconds and would produce a characteristic trace through the detector for the superheavy gravitinos we postulate.”

Among all currently existing detectors, the Chinese JUNO underground observatory seems predestined for such a search. It aims to determine the properties of neutrinos more accurately than has been possible until now, to observe neutrinos from cosmic, atmospheric, and geological sources, and to search for new particles beyond the Standard Model. Neutrinos do not interact with electromagnetic fields and rarely react with matter. In order to observe any reactions at all, neutrino detectors must therefore have extremely large volumes. In the case of the JUNO detector, this means 20,000 tons of an organic, synthetic oil-like liquid, commonly used in chemical industry, with special additions, in a spherical vessel with a diameter of approximately 40 meters. The search for gravitinos could be conducted in parallel and independently of neutrino reactions. The quantum chemistry of the scintillator oil and its specific properties would play a central role in the predicted effect. JUNO is scheduled to begin measurements in the second half of 2025.

 Unifying the forces of nature?

“The detection of the superheavy gravitinos we predicted would also be a major step forward in the search for a unified theory,” says Hermann Nicolai. “Since gravitinos are predicted to have masses on the order of the Planck mass, their detection would be the first direct indication of physics near the Planck scale and could thus provide valuable experimental evidence for a unification of the forces of nature — evidence that does not yet exist in this form.”



Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
+49 331 567-7303
elke.mueller@aei.mpg.de

Scientific contact:

Prof. Dr. Dr. h.c. Hermann Nicolai
Director emeritus
Tel:+49 331 567-7355
Fax:+49 331 567-7297
hermann.nicolai@aei.mpg.de


Publications

1. Kruk, A., Lesiuk, M., Meissner, K. A., Nicolai, H.
Signatures of supermassive charged gravitinos in liquid scintillator detectors
Phys. Rev. Research 7, 033145 (2025)
Source | DOI

2. Meissner, K.A., Nicolai, H.
Standard model symmetries and K(E10
J. High Energ. Phys. 2025, 54 (2025)
Source | DOI

Further information

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