Detector Simulation Physicist (EP-SFT-2026-152-GRAP)

As a Detector Simulation Physicist at CERN, you will join the Geant4 team to create and enhance GPU‑accelerated Monte Carlo detector simulation tools, with a special emphasis on optical photon transport. CERN is the European Organization for Nuclear Research, a global hub for cutting‑edge particle‑physics experiments and interdisciplinary scientific collaboration. Your everyday tasks will involve designing and implementing GPU algorithms that simulate optical photons inside a Monte Carlo particle‑transport framework. You will compare the GPU output with existing CPU‑based results, build unit, regression and physics‑validation test suites, and profile the code to locate and remove performance bottlenecks. Close cooperation with software groups from Large Hadron Collider experiments and active participation in the international Geant4 community are also part of the role, as is maintaining documentation and ensuring long‑term software quality. The position requires a national of a CERN Member or Associate Member State, a background in Physics, Computer Science or a related discipline, and either a master's degree with two to six years of post‑graduation experience or a PhD with up to three years of post‑graduation experience. Candidates must not have previously held a CERN fellow or graduate contract. Proven experience in scientific or physics‑simulation software development, especially using modern C++, and hands‑on work with GPU programming or heterogeneous computing architectures are essential. You also need solid practice in software testing, numerical validation, performance profiling or optimisation, and fluent written and spoken English with a willingness to learn French. Additional strengths that will be valued include familiarity with Monte Carlo methods or particle‑transport simulation, prior contributions to collaborative software projects, and experience with the Geant4 toolkit. Technical know‑how in CUDA, Python, Git, unit and regression testing, as well as proficiency with debugging and profiling utilities such as gdb, Compute Sanitiser, perf, Nsight Systems or Nsight Compute, are considered advantageous. The role is hybrid, 40 hours per week, and may require work during nights, Sundays or official holidays when the organization's needs dictate. What the role asks for: - National of CERN Member or Associate Member State - Master's degree in Physics, Computer Science or related field - 2–6 years post‑graduation experience (Master's) - PhD with ≤3 years post‑graduation experience (alternative) - No previous CERN fellow or graduate contract - Fluent English (written and spoken) - Commitment to learn French - Experience with modern C++ development - Experience in GPU programming or heterogeneous computing - Experience in software testing, validation or performance optimisation - Knowledge of Monte Carlo methods (nice‑to‑have) - Experience with Geant4 toolkit (nice‑to‑have) - Familiarity with CUDA (nice‑to‑have) - Familiarity with Python (nice‑to‑have) - Experience using Git for collaborative development (nice‑to‑have) - Ability to work nights, Sundays and holidays when required (nice‑to‑have)