Your responsibilities

At CERN, the European Organisation for Nuclear Research, physicists and engineers are pushing the boundaries of science and technology to explore the universe's more profound mysteries. The LHCb experiment investigates the tiny difference between matter and antimatter and searches for hints of new physics. The simulation software of the experiment is continually evolving to support the needs of more accurate and larger Monte Carlo samples, essential for physics analysis and the design of the detector's upgrade set to take place during the Long Shutdown 4 (2034-2035).

A new version of the Gauss simulation framework, based on an experiment-independent layer called Gaussino, is incrementally replacing the system in use to produce simulated samples. Gaussino combines the Gaudi functional framework and Geant4 toolkit, offers interfaces to HEP Generators, and lays the foundation for the simulation software needed by future experiments. The LHCb Simulation Team is currently integrating Machine Learning (ML) and GPU technologies within Gaussino and assessing their use with LHCb's full-scale cases.

We are looking for an Applied Physicist / Software Engineer with broad knowledge of detector simulation for HEP experiments and related software to participate in the ongoing program of work, ensure consistency, reliability, and flexibility of the simulation code and take the lead in shaping how to optimally exploit an heterogeneous computing environment for production of the diverse samples needed by LHCb.

As part of your responsibilities, you will:

• contribute to the development of Gaussino and Gauss, in particular in aspects related to GPUs and ML;
• explore the use of new techniques as available in the Gauss framework in a distributed heterogeneous production environment;
• ensure the deployment of a new easy and flexible infrastructure for the configuration of Gauss and Gaussino;
• contribute to the baseline support and maintenance of the LHCb simulation software.

Your profile

Skills:

• Broad knowledge of HEP simulation aspects, i.e. generators, detector geometry, particle transport, etc.
• Some experience with simulation software for HEP experiments, e.g. Pythia, Geant4, etc.
• Experience with HEP experiments code, software lifecycle, and building tools.
• Knowledge of programming techniques and languages (C++, Python, bash).
• Some knowledge of GPUs and ML would be an asset.
• 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 Particle Physics / Software Engineering (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.

Additional Information

Job closing date: 05.10.2025 at 23:59 CEST.

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

Working hours: 40 hours per week

Target start date: 01-November-2025

This position involves:

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

Job reference: EP-LBD-2025-141-GRAP

Field of work: Applied Physics

What we offer

• A monthly stipend ranging between 6287 and 6911 Swiss Francs per month (net of tax).
• Coverage by CERN's comprehensive health scheme (for yourself, your spouse and children), and membership of the CERN Pension Fund.
• Depending on your individual circumstances: installation grant; family, child and infant allowances; payment of travel expenses at the beginning and end of contract.
• 30 days of paid leave per year.
• On-the-job and formal training at CERN as well as in-house language courses for English and/or French.

About us

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. Find out more on http://home.cern.

We are on a Quest. A Journey into discovery like no other. Bring your expertise to our unique work and develop your knowledge and skills at pace. Join world-class subject matter experts on unique projects, in a Quest for greater knowledge and deeper understanding.

Begin your CERN Quest. Take Part!

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.