CERN LHCb Ntupling Service

I spent just over a year at CERN, the European Organisation for Nuclear Research, as an intern in the Open Data team. My office was in building 28, 50 metres from the Antimatter Factory. Fun fact: every day on my walk to lunch at Restaurant 2, I crossed the border from France into Switzerland.

The LHCb Ntupling Service lets physicists all over the world request custom, filtered datasets (called ntuples) from LHCb, one of the experiments at the Large Hadron Collider. They can download them without any experiment software, and the service gives them access to 55 petabytes of data. I built the request system around it, and I packaged its filtering feature, the Ntuple Wizard, as an npm package that other tools can reuse. The service was presented at the 2024 Conference on Computing in High Energy and Nuclear Physics, where it won the Poster Award by popular vote. I am also a co-author of the paper describing it, “LHCb Open Data Ntupling Service: On-demand production and publishing of custom LHCb Open Data”, published in EPJ Web of Conferences in 2025.

Besides the code, I guided official visits of the particle accelerator and the Antimatter Factory, explaining complex ideas to all kinds of audiences. I also built a pyramid out of cups, which became the highlight of the office (see picture). Most of all, I met so many great people from all over the world, and many of my friends from CERN now live in Zürich, where I now live too. CERN was also where I moved out of my parents’ house for the first time, and it was amazing for both my professional and personal development. I am very thankful to my supervisor Tibor Simko for welcoming me into his team and being a great mentor.