Data Reduction Physicist (EP-CMS-TDQ-2026-146-GRAP)

Job description

The NGT Real-time Reconstruction Revolution will transform the CMS High-Level Trigger into an offline-quality reconstruction facility processing up to 750 kHz of events. To make this sustainable, you will lead the design of two complementary data tiers: a low-level reconstructed format that enables trigger rates several times higher than conventional raw-data output while preserving the the option for future reprocessing, and a compact analysis format to save the full 750 kHz stream of online reconstructed events. Your responsibilities: Design next-generation data structures that push the limits of data reduction to save 750 kHz while preserving physics performance and analysis flexibility. Ensure all formats are accelerator-native (e.g., structure-of-arrays, SoA) and optimised for high-throughput GPU processing. Build an end-to-end framework to rigorously quantify the impact of lossy compression, with clear metrics, reference analyses, and automated regression tests. Benchmark compression/decompression under realistic workloads: CPU/GPU cost, I/O throughput, memory footprint, and latency. Advance lossless compression, leveraging R³-reconstructed objects and pioneering AI/ML techniques. Your profile: Demonstrated contributions to trigger and/or reconstruction in HEP (or comparable high-throughput scientific software). Practical understanding of of end-to-end HEP experiment operations, from detector readout to reconstruction, calibrations, datasets, and final physics results. Experience working in a large international collaboration (code review, CI/CD, documentation) is a plus. Knowledge with LHC experiments and their data formats is a plus. Expertise in data compression techniques is a plus. (lossless and/or lossy). Experience applying AI/ML methods (e.g., autoencoders) to data reduction is a plus. Proficiency in GPU programming and heterogeneous computing is a plus. Skills: High proficiency in C++, Python, and ROOT. Solid understanding of event reconstruction, including calibrations and commonly used data formats in HEP. Spoken and written English, with a commitment to learn French. Eligibility criteria: You are a national of a CERN Member or Associate Member State . You have a professional background in Physics (or a related field) and have either: a Master's degree with 2 to 6 years of post-graduation professional experience; or a PhD with no more than 3 years of post-graduation professional experience. You have never had a CERN fellow or graduate contract before. Job closing date: 25.09.2026 at 23:59 CEST. Contract duration: 24 months, with a possible extension up to 36 months maximum. Working hours: 40 hours per week Job flexibility: Fully Onsite Target start date: 01-January-2027 Job reference: EP-CMS-TDQ-2026-146-GRAP Field of work: Applied Physics Benchmark job: 200140 - Applied Physicist Global Benefits A monthly net stipend of either 6372 or 7004 Swiss Francs per month depending on your degree. 30 days of paid leave per year plus 2 weeks annual closure. Coverage by CERN’s comprehensive health insurance scheme (for yourself, your spouse and children), and membership of the CERN Pension Fund. Family, child and infant monthly allowances depending on your individual circumstances. A relocation package (installation grant and travel expenses) depending on your individual circumstances. Possibility to extend your contract up to 36 months. On-the-job and formal training including language classes. Overview of CERN - Discover a world where the impossible is made possible! At CERN, the European Organization for Nuclear Research, we are pushing the frontiers of science and technology. Our groundbreaking work brings together not only physicists but also a diverse range of professionals from engineering, technical, scientific, and administrative fields. Together, we foster an environment where innovation and collaboration thrive. Every day, we face exciting new challenges and opportunities to contribute to cutting-edge research that shapes our understanding of the universe. We meet these challenges through the diverse perspectives within our teams, ensuring every contribution is valued and driving our shared sense of inclusion and purpose. Diversity is a core value of CERN since its foundation, and it remains central to our mission and continued success. If you are ready to be part of a dynamic, inclusive community pushing the boundaries of knowledge, CERN is the place where your curiosity and skills can thrive. Be part of our mission to uncover what lies at the heart of the universe! TAKE PART! More information about us, here: