Data Reduction Physicist - European Organization for Nuclear Research (Geneva)

About this position

The summary below is published by European Organization for Nuclear Research on the official vacancy notice. Our own analysis — salary realism, comparable openings, career trajectory, language profile — follows further down the page.

Key responsibilities

According to the vacancy notice, the role centres on the following duties:

• Design next-generation data structures for data reduction while preserving physics performance and analysis flexibility
• Ensure all formats are accelerator-native (structure-of-arrays, SoA) and optimised for high-throughput GPU processing
• Build an end-to-end framework to 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

Are you eligible?

Check these requirements from the notice before investing time in an application:

• Education: Master's degree with 2 to 6 years of post-graduation professional experience, or PhD with no more than 3 years of post-graduation professional experience, in Physics or a related field
• Experience: Demonstrated contributions to trigger and/or reconstruction in HEP or comparable high-throughput scientific software; practical understanding of end-to-end HEP experiment operations from detector readout to reconstruction, calibrations, datasets, and final physics results
• Languages: English (spoken…), French (commitm…)
• Key skills: High proficiency in C++, High proficiency in Python, High proficiency in ROOT, Solid understanding of event reconstruction, including calibrations and commonly used data formats in HEP, Spoken and written English
• Eligibility: You are a national of a CERN Member or Associate Member State; you have never had a CERN fellow or graduate contract before

Contract and working arrangements

Contract duration: 24 months, with a possible extension up to 36 months maximum.

Working arrangements: Fully Onsite.

Hiring unit: EP-CMS-TDQ.

Position details

Reference

EP-CMS-TDQ-2026-146-GRAP

Last Verified

15 September 2026

Position overview

This is the official EU Careers listing for Data Reduction Physicist at CERN based in Geneva (Other). The vacancy reference is EP-CMS-TDQ-2026-146-GRAP. The role falls under the Research domain.

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:careers.cern

Application timeline

This vacancy was first listed on 4 September 2026, 11 days ago.

No closing date is published in the source feed for this position. EU vacancies typically remain open for four to eight weeks; check the official vacancy notice for the cut-off date and time.

Last verified against the EU Careers feed on 15 September 2026.

Where to learn more

For headcount, mission, and other open vacancies at CERN see the CERN institution page; for the cost of living, correction coefficient, and other postings in Geneva see our Geneva location page; for related vacancies in the Research field browse our Research domain page.

New to EU careers? Our beginner's guide walks through entry routes, EPSO competitions, and what to prepare. For application logistics see application tips and EPSO competitions.