CMS completes Run-1 heavy ion open data collection

New release of simulations, proton-lead collision data, and proton reference data

The CMS experiment's extensive collection of heavy ion data from LHC Run-1 (2010–2013) is now accessible through the CERN Open Data portal. Today’s release of proton-lead data taken at 5.02 TeV collision energy in 2013 adds to the previously available lead-lead collision data. This accomplishment marks CMS's commitment to open-data sharing, as all proton-proton and heavy ion collision data from the first LHC data-taking period have been made available to the global community within just ten years.

A proton-lead collision event recorded by CMS in 2013 and available in the latest release of CMS Open Data. Go [here](https://cms3d.web.cern.ch/HIRun2013/) to explore this event!

This release batch consists of a substantial 219 TB of proton-lead data. Furthermore, it includes 49 TB of proton-proton reference data, which matches the collision energy of the heavy ion data. Also provided are 22 TB of proton-proton reference data for the previously released heavy ion data at a collision energy of 2.76 TeV. For the first time, heavy ion simulations, corresponding to the variety of CMS heavy ion collision data, are incorporated in the release.

To facilitate researchers’ access to these data, CMS provides a computing environment and software for open data users to get started with their analyses. In the future, as resources permit, advanced examples and tutorials of analysis usage will enrich the initial “getting started” instructions, as CMS currently does for the proton-proton open data.

All these resources are easily discoverable with a “heavy-ion physics” keyword search on the CERN Open Data portal.

This milestone release of CMS's heavy ion data, complemented by associated software and simulations, will undoubtedly foster the long-term preservation and reusability of these valuable resources.