Applications are invited for a postdoctoral research position at CPPM to work on the ATLAS experiment starting September 2025.

Located in the heart of the Parc National des Calanques, on the Luminy campus, the CPPM is a joint research laboratory of the CNRS and Aix-Marseille University, with around 180 researchers, engineers and PhD students. The laboratory studies subjects ranging from particle physics to astroparticle physics and cosmology, with a strong technological focus on electronics, mechanics, instrumentation and computing, enabling the design and construction of cutting-edge detection systems, often called upon to operate under extreme conditions: in the depths of the sea, in space or underground. Most of our research is carried out as part of leading international scientific collaborations, and our contributions are recognized worldwide. CPPM is committed to ethical research and promotes diversity and inclusion in the workplace, and provides administrative and logistical support to newcomers, particularly PhD students. (more details here: https://www.cppm.in2p3.fr/web/fr/index.html).

The ATLAS group at CPPM consists of approximately fifty persons, including fourteen physicists and five doctoral students. The group has played a major role in the design and construction of the electromagnetic calorimeters, the pixel tracker, and the trigger system of the ATLAS detector. It has also significantly contributed to the discovery of the Higgs boson and is now focusing on the study of the the production of Higgs boson pairs to measure the Higgs boson self-coupling. In addition to making essential contributions to the analysis of data recorded by ATLAS, the group is pursuing important efforts to upgrade the detector, particularly its Liquid Argon (LAr) calorimeter, to adapt it to the planned improvements of the LHC accelerator, especially the substantial increase in luminosity.

The Phase-II upgrade of the ATLAS detector will prepare it for the high luminosity phase of the LHC (HL-LHC), increasing its discovery potential. The ATLAS group at CPPM is responsible for the design and production of the readout electronic board for the Phase-II upgrade of the LAr calorimeter. This board is equipped with cutting-edge FPGAs capable of running complex algorithms. The CPPM is leading a project aimed at developing neural networks that can run on these FPGAs to enhance energy resolution in the calorimeter under the high pileup conditions of the HL-LHC. The CPPM is also heavily involved in photon reconstruction and identification, leveraging its experience with the LAr calorimeter. This expertise is used to take a leading role in the search for the production of Higgs boson pairs decaying into two photons and two b-jets (HH -> bbγγ). The successful candidate is expected to play a leading role in preparing the upgrade of the LAr calorimeter, particularly in studies related to the impact of this upgrade on photon reconstruction. He or she is also expected to contribute to the search for HH -> bbγγ with ATLAS Run3 data and prepare this search for the HL-LHC era. The successful candidate will work in a team composed of three permanent researchers and two PhD students.

The neural networks used to compute energies in the LAr calorimeter have already been developed and implemented in the ATLAS LAr readout electronics simulation system. In addition, a PhD student is currently working on improving these networks. The successful candidate is expected to lead an effort aimed at quantifying the improvement in photon reconstruction and identification due to the use of these neural networks in the LAr readout electronics. He should adapt the reconstruction of electromagnetic clusters and photons in the calorimeter, as well as the subsequent calibration and identification of photons, to leverage the improved energy resolution in individual cells. Contributions to enhancing the LAr neural network and/or developing additional machine learning techniques to improve photon identification are also considered. The impact of these improvements on measurements involving H->γγ at the HL-LHC is expected. In parallel, the candidate will contribute to the current HH->bbγγ search with ATLAS Run3 data, collaborating with another PhD student working on this subject at CPPM. The position is based at CPPM for two years with frequent travel to CERN.

The successful candidate must hold a PhD in particle physics and have a maximum of two years’ of postdoctoral work experience. Experience with programming languages such as C++ and Python is required. Experience in machine learning is an asset, but not mandatory. Strong communication skills in English are expected.

Applications should be submitted on the CNRS job portal: https://emploi.cnrs.fr/Offres/CDD/UMR7346-ANNPOR-154/Default.aspx?lang=EN

Candidates should arrange for 3 letters of recommendation to be sent directly to aad@cern.ch.

The position is open until filled. Applications will be considered starting first of June 2025.

For more information please contact Georges Aad (add@cern.ch).