About ALICE

ALICE is the acronym for A Large Ion Collider Experiment, the experiment at the Large Hadron Collider devoted to the physics of matter at infinitely small scale exploiting heavy-ion collisions. Its scientific programme aims at answering a series of fundamental questions such as:

• What is the phase of matter under extreme conditions of temperature, 200'000 times larger than the temperature at the center of the Sun ?
• What generates the mass mass of ordinary matter such that the protons and neutrons weight 100 times more than the quarks they are made of ?
• What is the dynamics of the strong interaction that binds quarks inside ordinary matter ? You can find more information on the ALICE detector and physics on the ALICE website

About ALICE Data

The following are provided through this portal:

• Primary and derived datasets

  • The available primary ALICE datasets contain a limited sample of specially selected interaction events recorded from pp and PbPb collisions collected in 2010. The data format is the ESD (event summary data) format generated by the ALICE raw data reconstruction software. These datasets are not corrected for detector inefficiency nor statistically representative and therefore cannot be used to perform full fledged scientific studies. They rather serve to demonstrate the use of the ALICE analysis tools.
  • A set of simplified datasets derived from the primary ones for use in the provided masterclass analyses. These data contain exclusively the information needed by the masterclasses and are not useful for a different purpose.

• Tools

  • A downloadable Virtual Machine (VM) image with the ALICE software environment which allows to access the above datasets
  • An analysis example chain running in the VM, reading a primary dataset using the ALICE analysis framework. The sources for the example can be adapted and recompiled by the user to look at different features of ALICE data. This exercise requires a minimal understanding of the usage of the analysis framework.
  • Source code for the various examples and applications used by the ALICE masterclasses

Primary Datasets formats

Data in the primary datasets are in a format known as ESD (Event Summary Data), produced by the ALICE reconstruction procedure

• The Event Summary Data (ESD) contains lists of reconstructed tracks/particles and global event properties. ESD files contain the information that is needed for the analysis:

  • All the high-level physics objects (such as muons, electrons, etc.);
  • Tracks with associated hits, calorimetric clusters with associated hits, vertices;
  • Information about event selection (triggers), data needed for further selection and identification criteria for the physics objects.
  • An ESD file is not the final event interpretation with a simple list of particles, but just its best current understanding that takes into account several parameters

Disclaimer

• The open data are released under the Creative Commons CC0 waiver. Neither ALICE nor CERN endorse any works, scientific or otherwise, produced using these data.
• All released data samples will have a unique DOI that you are requested to cite in any applications or publications.
• Despite being processed, the high-level primary datasets remain complex and selection criteria need to be applied in order to analyse them, requiring some understanding of particle physics and detector functioning. The data cannot be viewed in simple data tables for spreadsheet-based analyses.
• ALICE had just started data taking in 2010 and the methods are evolving, in particular to respond to the evolving beam conditions of the LHC.