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Limitations

Although these data are all intended for use in scientific research, they are not without limitations. It is important to keep in mind the limitations of these datasets when using them in order to avoid false-positive results or dead ends. Although some of the most important limitations are documented here, if you have any questions about whether a particular analysis is possible please feel free to contact us. In case the analysis is not possible with the available public data, you are also welcome to consider a short term association with ATLAS in order to perform the analysis like a member of the collaboration would.

Data format limitations​

The HEPMC2 event-generation data format released for research use contains all particles in the event record, slightly modified from what the generator would normally provide. In particular:

  • Loops in the event record have been broken apart.
  • The events have been checked for unexpected features (like stable gluons), and any such events have been removed. These can result from rare issues in specific event generators.

The data format is without any detector simulation applied. It is necessary, therefore, to apply some smearing and inefficiencies to the particle records before comparing them to reconstructed data. Doing so is rather delicate, but standard programs like DELPHES and PGS, as well as Rivet functionality, should suffice for many cases.

Data sample limitations​

The samples that have been released are sufficient to establish standard backgrounds and generically-applicable systematic uncertainties. In some cases, establishing key systematic uncertainties requires additional samples that have not been released (e.g. heavy quark fragmentation variations for top mass measurements). Some signal samples or variation samples have also not been released in order to reduce the total space required by the samples (e.g. W-boson mass variation samples that are required for a template fit to the W-boson mass, or a wide variety of beyond-the-Standard-Model signal samples that are used in various searches for new particles).

In principle it is possible to produce your own samples. The tutorials provided by the collaboration provide instructions for doing so. In case issues are encountered, you are welcome to get in touch with us for assistance. Of course, the collaboration has significant computing resources that have been used for production of very large samples. It can be difficult for individuals to produce a comparable number of events, and it can be quite wasteful in case the reproduction duplicates what has already been done internally.

In case there are specific samples that would be beneficial to your analysis or work, you are welcome to request their release.