Key Points

Introduction

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• Finding the data is non-trivial, but all the information is on the portal
• A careful understanding of the search options can help with finding what you need

Where are the datasets?

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• Use the filter selections in the left-hand sidebar of the CERN Open Data Portal to find datasets.

What data and Monte Carlo are available?

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• The collision data are directed to different datasets based on trigger decisions.
• The Monte Carlo datasets contain a specific simulated physics process.

How to access metadata on the command line?

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• cernopendata-client is a command-line tool to download dataset files and metadata from the CERN Open Data portal.

What is in the datafiles?

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• It’s useful to inspect the files before diving into the full analysis.
• Some files may not have the information you’re looking for.

Finding and exploring a NanoAOD dataset

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• Use the CERN Open Data Portal search filters (experiment, year, file type, category) to efficiently locate specific simulation datasets.
• Dataset names encode the physics process, particle mass and width, collision energy, and generator software.
• cernopendata-client retrieves file locations programmatically, making it easy to script dataset access.
• NANOAODSIM files contain the same reconstructed-object variables as collision NANOAOD files, plus generator-level information such as GenPart_* and genWeight.