APC

The Astroparticule and Cosmology (APC) laboratory was created in 2005 and is co-directed by CNRS and Université Paris-Cité. It includes 220 people whose activities are organised around five scientific groups: cosmology, gravitation, high-energy astrophysics, experimental particle physics, and theoretical physics. APC is in particular a leading laboratory in France for multi-messenger astrophysical studies, being involved in a wide range of key experiments in the field. APC is participating in SVOM, ATHENA et INTEGRAL for the X and gamma-ray observations and in H.E.S.S. and CTA for high-energy photon searches. APC is also involved in the LIGO-VIRGO-KAGRA gravitational wave detector collaboration and, for neutrino and dark matter detection, participates in the ANTARES, KM3NeT, DUNE, and DarkSide experiments. Finally, APC includes a theoretical physics department which includes several renowned experts in cosmic-ray propagation and in the modelling of multi-messenger signatures from various cosmic sources. In addition to ACME, APC is part of the European Consortium of Astroparticle Physics (ApPEC) that coordinates national efforts in astroparticle physics research across Europe.

Main contact for TNA call: Sonia El Hedri

Within the framework of ACME, APC will provide expertise on multi-messenger signature modelling, as well as on data analysis for neutrino experiments and for telescopes targeting gamma rays, X rays, and high-energy photons.

Concerning neutrinos, the ANTARES/KM3NeT group has a longstanding experience in searches for core-collapse supernovae, for the Galactic diffuse neutrino flux, and for neutrinos from point-like sources (using external catalogues). The group has in particular developed searches based on catalogues of sources identified by VLBI, gamma-ray, gravitational-wave, and neutrino (IceCube) observatories. To constrain the neutrino fluxes associated with given sources or object populations, the group has designed likelihood analyses and devised new methods to evaluate the ANTARES and KM3NeT Point Spread Functions (PSF) and backgrounds. Moreover, for diffuse flux searches, the group has developed a bootstrap method to evaluate expected signals without relying on PSFs. Additionally, the group is exploring analyses based on a joint optimization of the neutrino and gravitational-wave/gamma-ray event selection criteria. Here, the group is involved in a search for sub-threshold gravitational wave events and in the incorporation of neutrino analyses to the Gammapy software.

In addition to the tools listed below, the team is working on a neutrino analysis software for the ANTARES and KM3NeT telescopes. This software will allow users to probe neutrino emission from point-like sources, using their own source catalogues, and from the Galactic Plane, using their own neutrino diffuse emission model. Additionally, this software will enable researchers to evaluate the Instrument Response Functions (IRFs) of ANTARES and KM3NeT, that is, the expected signal acceptances, background levels, energy resolution functions, and point spread functions over a given search period. The APC neutrino group will train researchers who wish to either apply the available analysis tools to custom neutrino emission models, or use the existing IRFs to explore other neutrino energy regimes.

The gamma-ray group of the Astroparticle & Cosmology laboratory is an historical group of the French TeV gamma-ray astronomy. The members are working on different astrophysical topics within galactic sources (supernova remnants, pulsar, pulsar wind nebula, Galactic center) and extragalactic sources (Active Galactic Nuclei), studying particle acceleration processes, cosmic-rays diffusion and advection within the interstellar medium, extragalactic background light and galactic diffuse emissions. These researches are realised on the theoretical side and with experimental data analysis, mainly within the H.E.S.S. collaborations. In addition, the group’s analysis skills for radio, X-ray and GeV data permit multi-wavelengths analyses and astrophysical interpretations. The team is also strongly involved in the construction of the CTAO observatory (camera timing board, Science Analysis Tool, Proposal Handling System, data modelling and science operations) and in the scientific preparation of the CTAO consortium (e.g. AGN population, galactic plane survey, PeVatron search).

The APC theory group will provide a strong expertise in the modelling of cosmic-ray propagation and of multi-messenger signatures for both diffuse emission and point-like sources. The group has in particular proposed a new model for the diffuse gamma-ray and neutrino emission from the Galactic Plane, and for gamma-ray, neutrino, and cosmic-ray emission from Active Galactic Nuclei and microquasars. The team is developing and supporting the Multi-Messenger Online Data Analysis platform (MMODA), a platform which enables the analysis of data from electromagnetic (radio to gamma-ray), neutrino, and gravitational-wave observatories.

Involved scientists

Julien Aublin is an assistant professor at APC, Université Paris Cité. He is a member of the ANTARES and KM3NeT collaborations. Since 2017, he has led ANTARES searches for neutrino signals coinciding with blazars identified via Very Long Baseline Interferometry [], and with point sources identified by various detectors (IceCube High-Energy neutrinos, gamma-ray sources, ultra-high-energy cosmic ray sources) []. Additionally, he has been working on the characterisation of a potential diffuse neutrino flux coming from the Milky Way, which is a major focus of his current research. The analyses that he developed are based on a maximum likelihood method, that involves the characterisation of the detector’s response to build the probability density functions that are used to discriminate between signal and background. In particular, Julien Aublin has an extended knowledge of the procedures used to compute the ANTARES and KM3NeT Point Spread Functions (PSFs) and parameterise them as a function of the energy, declination, and other relevant variables. Finally, for the ANTARES search of a diffuse/extended signal from the Galactic Plane, he has developed, with his Ph. D. student Théophile Cartraud, a bootstrap method that allows to convolve directly the detector’s response with the considered astrophysical signal model, without the need of a PSF. The code is planned to be used with KM3NeT data and in combination with other collaborations like IceCube.

Alexis Coleiro is a CNRS astrophysicist (Chargé de Recherche) working at APC and a member of the SVOM, ANTARES, and KM3NeT collaborations. He is an expert in multi-messenger and multi-wavelength astronomy, with extensive experience utilizing optical and near-infrared facilities and performing data reduction for X-ray instruments. He is actively involved in the SVOM space mission, particularly in the reduction and analysis of hard X-ray coded-mask imaging data. He is also proficient in designing and executing multi-messenger observational campaigns and integrating neutrino detections with multi-wavelength follow-up strategies.

Antonio Condorelli is a CNRS/ACME postdoctoral researcher at APC. He is an expert in the phenomenology of ultra-high-energy cosmic rays (UHECR) and multi-messenger astrophysics. From 2016 to 2023, he has been a member with the Pierre Auger Collaboration and worked on linking features observed in the cosmic ray spectrum and composition to the properties of their sources. He is the main developer of SimProp, one of the most widely used propagation codes in the UHECR community. He also took part in the development of a public software tool for UHECR studies (as part of the MICRO international project), which includes arrival direction information and the calculation of associated secondary particles, such as gamma rays and neutrinos. In 2024, Antonio Condorelli joined the KM3NeT collaboration, where he focuses on air-shower simulations to improve estimates of the muon background expected in the detectors. He is also currently working on identifying events at the highest energies within the KM3NeT/ARCA framework and is collaborating with Sonia El Hedri, Bruno Khélifi, and Régis Terrier to integrate neutrino analyses into the Gammapy software.

Sonia El Hedri is a CNRS researcher (Chargée de Recherche) at APC . She is an expert in the search of thermal (10s of MeV) neutrinos from Core-Collapse Supernovae (CCSNe). From 2018 to 2021 she played a leading role in the search for the Diffuse Supernova Neutrino Background with the fourth data-taking phase of the Super-Kamiokande detector []. Since 2021 she joined the ANTARES and KM3NeT collaboration, and has been leading the APC ANTARES/KM3NeT group since September 2024. She is currently focusing on real-time searches for CCSN neutrinos with KM3NeT, as well as on combined studies involving multiple next-generation detectors such as Hyper-Kamiokande, DUNE, and DarkSide-20k []. As part of these studies, she made contributions to the SNEWPY software []. She is currently participating in KM3NeT searches for neutrinos associated with gravitational waves and gamma rays. In particular, she is working with Antonio Condorelli, Bruno Khélifi, and Régis Terrier, on incorporating neutrino analyses into the Gammapy software.

Bruno Khélifi is a CNRS astrophysicist (Chargé de Recherche) working at APC and is leading the APC CTA group in association with Régis Terrier. He is a member of the H.E.S.S., CTAO, and SWGO collaborations and has extensive expertise in very-high-energy gamma ray astronomy. His expertise ranges from data calibration to analysis (from raw data to astrophysical products). In particular, he is responsible for one of the three C++ pipelines of the H.E.S.S. data workflow. He is currently investigating the astrophysical system pulsar/pulsar wind nebula, on the hunt of Galactic PeV particle accelerators. He is also the project manager of the open Python library Gammapy, aiming to analyse high-level gamma-ray data. Finally, he is the convener of the open initiative ‘Very-high-energy Open Data Format’ (VODF).

Antoine Kouchner is a professor at APC, Université Paris Cité, as well as the coordinator of the ACME project, the spokesperson of ANTARES, and a member of the KM3NeT collaboration. His is an expert in the elaboration of simulations and of data analysis techniques for neutrino experiments. He is currently involved in the search for neutrinos from the plane of the Milky Way, in collaboration with Julien Aublin and a Ph. D. Student Théophile Cartraud.

Mathieu Lamoureux is a postdoctoral researcher, ACME technical coordinator, and member of the KM3NeT collaboration (he was also part of Super-Kamiokande, Hyper-Kamiokande, and IceCube in the past years). He focuses on the search for neutrino counterparts to sources observed with other messengers (e.g., binary mergers detected in gravitational waves). He is the lead developer of MOMENTA software that aims to gather data from several neutrino telescopes to derive astrophysical constraints on transient sources. He is involved in the development of the KM3NeT real-time framework, co-convenor of the KM3NeT Astronomy working group member of the Open Science Committee in KM3NeT.

Andrii Neronov is a professor at APC, Université Paris Cité and is a member of the LHAASO and CTAO collaborations as well as an expert in the modelling of multi-messenger signatures from a wide range of sources. He has in particular proposed models of gamma-ray, neutrino, and cosmic-ray emission from Active Galactic Nuclei, microquasars, and extended sources such as the plane of the Milky Way. For the latter, in collaboration with Dmitri Semikoz (APC), he has proposed new numerical models for cosmic-ray propagation, associated with characteristic neutrino spatial distributions and energy spectra. He is the Principal Investigator of the LACTEL experimental project, which aims at building a Cherenkov detection array in the Geneva Lake to study electrons and positrons from cosmic rays. Finally, together with Denys Savchenko and an international team, he is developing and supporting the Multi-Messenger Online Data Analysis platform.

Denys Savchenko is a research engineer (Chef de projet ou expert en Ingéniérie logicielle) at APC, Université Paris Cité and is an expert in the multi-messenger data analysis and scientific cloud computing. He is one of the key developers and DevOps engineers of the Multi-Messenger Online Data Analysis platform, which he develops together with Andrii Neronov, and an international team. Recent achievements, together with Andrii Neronov and Dmitri Semikoz, include the detection of an extended neutrino emission from the Cygnus region using open data of IceCube, and a discovery of the strong evidence that the population of Seyfert galaxies is a neutrino source class. He is an associated member of the LHAASO collaboration (full membership from 2025).

Régis Terrier is a CNRS researcher (Directeur de recherche) at APC. He is a member of the CTAO consortium and the H.E.S.S. and SWGO collaborations. He is the APC H.E.S.S. group leader. He is lead developer of the Gammapy library. His scientific activities are centered on high energy processes in the Galactic Centre region from the supermassive black hole activity to cosmic-ray acceleration as well as accelerators in the Galaxy with observations in both X-ray and gamma-ray bands. Because of the importance of joint analysis of multi-wavelength and multi-messenger for the field, he is active in opening Gammapy’s modeling capabilities beyond gamma-ray instruments, in X-rays and neutrino together with other team members.