19. Skims

The skim package is a collection of high-level analysis scripts that reduce the data set to a manageable size by applying a simple selection. The input to a skim are Belle II File Format files of processed data. The output are so-called User-defined DST Output (udst) files. These files actually contain more information but fewer events.


Analysts are recommended to use skimmed udst files as input to their analysis. For an introductory lesson, take a look at Section 25.4.12.


If you would like to know which skims are available, please browse the Physics skims section of the documentation. If you would like to know which cuts are made by a particular skim, then consult the source code by clicking the [source] button on that skim in Physics skims, or by navigating to skim/scripts/skim/WGs/<your working group name>/ in the basf2 repository.

Changed in version release-06-00-00: The skim package was reorganised between releases 5 and 6. If you need your skim steering files to work with both release 5 and release 6, then please use the following type of try-except block:

    # release 6+ imports
    from skim import BaseSkim, CombinedSkim
    from skim.WGs.ewp import BtoXll
except (ImportError, ModuleNotFoundError):
    # release 5 imports
    from skimExpertFunctions import BaseSkim, CombinedSkim
    from skim.ewp import BtoXll

19.1. Systematics skims

19.2. Physics skims

19.3. Standard skim lists

19.4. Information for skim experts