Applied Physicist

Job Posting Organization:
CERN, the European Organization for Nuclear Research, is a leading scientific research institution established in 195

• It is known for its groundbreaking work in the field of particle physics and is home to the Large Hadron Collider, the world's largest and most powerful particle accelerator. CERN employs over 2,500 staff members and collaborates with thousands of scientists from around the globe, representing more than 100 nationalities. The organization operates in multiple countries and is dedicated to pushing the frontiers of science and technology, fostering an environment of innovation and collaboration.

Job Overview:
The position of Applied Physicist at CERN involves leading the design of innovative data structures for the NGT Real-time Reconstruction Revolution project. This project aims to transform the CMS High-Level Trigger into a facility capable of processing up to 750 kHz of events with offline-quality reconstruction. The successful candidate will be responsible for creating two complementary data tiers: a low-level reconstructed format that allows for significantly higher trigger rates while maintaining the option for future reprocessing, and a compact analysis format to accommodate the full stream of online reconstructed events. This role requires a deep understanding of high-energy physics (HEP) and the ability to design data structures that optimize data reduction without compromising physics performance or analysis flexibility. The candidate will also build an end-to-end framework to assess the impact of lossy compression and benchmark various performance metrics under realistic workloads, ensuring the advancement of lossless compression techniques and improving raw data structures for better compressibility and access speed.

Duties and Responsibilities:

• Design next-generation data structures that enhance data reduction while maintaining physics performance and analysis flexibility.
• Ensure all data formats are accelerator-native and optimized for high-throughput GPU processing.
• Build a comprehensive framework to quantify the impact of lossy compression, including metrics, reference analyses, and automated regression tests.
• Benchmark compression and decompression processes under realistic workloads, focusing on CPU/GPU costs, I/O throughput, memory footprint, and latency.
• Advance lossless compression techniques, utilizing R³-reconstructed objects and innovative AI/ML methods.
• Improve the structure of raw data to achieve higher compressibility and faster access times.
• Collaborate with a large international team, participating in code reviews, CI/CD processes, and documentation efforts.

Required Qualifications:
Candidates must demonstrate contributions to trigger and/or reconstruction in high-energy physics or comparable high-throughput scientific software. A practical understanding of end-to-end HEP experiment operations, including detector readout, reconstruction, calibrations, datasets, and final physics results, is essential. Experience in large international collaborations, knowledge of LHC experiments and their data formats, and expertise in data compression techniques (both lossless and lossy) are highly desirable. Familiarity with AI/ML methods, particularly in data reduction, and proficiency in GPU programming and heterogeneous computing will be advantageous.

Educational Background:
Applicants must be nationals of a CERN Member or Associate Member State and possess a professional background in Physics or a related field. Candidates should hold 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. It is important that candidates have not previously held a CERN fellow or graduate contract.

Experience:
The position requires a professional background in Physics or a related field, with specific experience in high-energy physics or high-throughput scientific software. Candidates should have a minimum of 2 years of relevant experience post-graduation for those with a Master's degree, or up to 3 years for those with a PhD. Experience in international collaborations and familiarity with HEP experiment operations will be beneficial.

Languages:
Proficiency in spoken and written English is mandatory, with a commitment to learn French being a plus. Knowledge of additional languages may enhance a candidate's profile but is not required.

Additional Notes:
The contract duration for this position is 24 months, with the possibility of extension up to a maximum of 36 months. The working hours are set at 40 hours per week, and the position is fully onsite. The target start date for the role is March 1, 202

• The job reference is EP-CMG-2026-13-GRAP, and it falls under the field of Applied Physics. The compensation includes a monthly stipend ranging from 6,372 to 7,004 Swiss Francs, which is tax-free, along with 30 days of paid leave per year, comprehensive health insurance coverage, family allowances, and a relocation package depending on individual circumstances. Additionally, on-the-job and formal training, including language classes, will be provided.