Lead Simulation Physicist - High-Performance Detector Simulation (EP-SFT-2026-136-LD)

At CERN, the European Organization for Nuclear Research, physicists and engineers are probing the fundamental structure of the universe. Using the world's largest and most complex scientific instruments, they study the basic constituents of matter - fundamental particles that are made to collide together at close to the speed of light. The process gives physicists clues about how particles interact, and provides insights into the fundamental laws of nature.

Introduction:

In this role you will be responsible for developing, maintaining, and validating physics simulation software used to model particle interactions in high-energy physics (HEP) detectors. Working within the Geant4 Simulation team, you will contribute to ongoing efforts to extend physics coverage, improve modelling capabilities, and enhance computing performance.

A major focus of the role is the development of detector and physics simulations for GPU and other parallel computing architectures, supporting the growing computational demands of the High-Luminosity LHC and future experiments. You will play an important role in advancing both physics models and the efficiency of their implementation in high-performance computing environments. 

Functions:

• Further develop the Geant4-based GPU-enabled component, AdePT, ensuring its smooth integration into the LHC experiments' software frameworks, and lead the consolidation and implementation of key components, possibly including relevant physics processes.
• Design and run regression tests comparing GPU results against CPU reference physics, ensuring no degradation in physics fidelity.
• Coordinate with LHC experiments (ATLAS, CMS, LHCb, ALICE) and FCC studies to prioritise related developments.
• Contribute to the overall project organisation, including work planning, organising workshops and training activities, and representing the project and its vision.
• Engage with Geant4’s worldwide user community, foster collaboration within the SFT group, the EP department, CERN, and external partners, and encourage contributions from laboratories and universities.
• Supervise team members and coordinate tasks relevant to the Geant4 project.

• PhD or equivalent relevant experience in the field of Physics or a related field.

Experience:

• Demonstrated experience with Monte Carlo techniques applied to particle transport simulation, particularly their implementation using modern software technologies and hardware architectures such as GPUs.
• Proficiency in scientific computing and deep knowledge of advanced programming.
• Knowledge in large collaborative software projects, particularly Monte Carlo simulation toolkits, relying on continuous integration, code reviews, as well as issue-based workflows.
• Experience with tools and methods that support all phases of the life cycle of large scientific code bases particularly software design, development, testing, and performance optimisation.
• A strong track record of scientific publications and high-level communication (for example, through invited conference presentations).
• Experience in supervising and managing external contributors would be considered an advantage.

Technical competencies:

• Simulation, design and development of (parts of) detectors: geant4.
• Knowledge of programming techniques and languages: C++, CUDA, Python.
• Development of application software.
• Testing, diagnosing and optimisation of software: unit tests, physics regression tests, GPU profiling.
• Knowledge and application of software life-cycle tools and procedures: would be considered an advantage (e.g. GitLab CI, JIRA, Spack or Conda).

Behavioural competencies:

• Achieving Results: having a structured and organised approach towards work; being able to set priorities and plan tasks with results in mind.
• Learning and Sharing Knowledge: sharing knowledge and expertise freely and willingly with others; coaching others to ensure knowledge transfer.
• Demonstrating Flexibility: adapting quickly and resourcefully to shifting priorities and requirements.
• Communicating Effectively: expressing opinions, ideas and suggestions with conviction and in a logical/structured manner; keeping to the point.
• Solving Problems: finding the information needed to solve problems; making objective judgments based on all the facts available.

Language skills:

• Spoken and written English, with a commitment to learn French.

Eligibility and closing date:

Diversity has been an integral part of CERN's mission since its foundation and is an established value of the Organization. Employing a diverse workforce is central to our success. We welcome applications from all Member States and Associate Member States.

This vacancy will be filled as soon as possible, and applications should normally reach us no later than 19.07.2026 at 23:59 CEST.

Employment Conditions:

Contract type: Limited duration contract (5 years). Subject to certain conditions, holders of limited-duration contracts may apply for an indefinite position.

Working Hours: 40 hours per week

Job Flexibility: Hybrid

This position involves:

• Work during nights, Sundays and official holidays, when required by the needs of the Organization.

Job grade: 6-7

Job reference: EP-SFT-2026-136-LD

Field of work: Experimental Physics

Benchmark Job Title: Applied Physicist

Global Benefits

• A competitive salary (tax free), increasing in line with your years of relevant experience.
• 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, removal, travel expenses) depending on your individual circumstances.
• Possibility to extend your contract up to 8 years + eligibility for indefinite contract tenure.

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