8.2. B2BII Analysis#

8.2.1. Prerequisites#

The recommended versions to be used are release-06-00-08 or the latest light release.

8.2.2. B2BII Converter#

The most straightforward way to perform the analysis is to execute the B2BII Converter on-the-fly, meaning in the same job as the physics analysis is performed (reconstruction of specific decay, …, producing flat ntuples for offline analysis). Note that it’s also possible (and is as well more convenient) first to produce the converted ROOT files in the Belle II MDST format and then run the analysis script over converted ROOT files.

Global tags#

As all basf2 analysis, the necessary payloads are handled by basf2 and are stored in the corresponding global tags in the conditions database at BNL.

To avoid creating excess load to the BNL server, we have prepared a local database cache at KEKCC, which includes B2BII, B2BII_MC, BellePID, b2bii_beamParameters_with_smearing, and analysis_tools_light-2012-minos global tags.

If you use an older release than release-05-02 or light-2103-oceanos, the following two lines must be added in the beginning of your b2bii analysis script:

basf2.conditions.metadata_providers = ["/sw/belle/b2bii/database/conditions/b2bii.sqlite"]
basf2.conditions.payload_locations = ["/sw/belle/b2bii/database/conditions/"]

Warning

When doing the two-step procedure (1. convert and 2. analyse), please be sure these two lines are also added in the script for step 2, if you are using a release older than the recommended ones.

It is very easy to run any existing basf2 analysis python script over the Belle MC or data. If you already have a working basf2 physics analysis python script that performs some kind of reconstruction, you simply need to replace the loading of Belle II MDST files with the Belle MDST files and executing the conversion.

To load Belle MDST file(s) and to convert them use convertBelleMdstToBelleIIMdst. This function has input parameters to specify the input MDST files to be converted, flag to specify whether or not the fix_mdst should be applied or not (it should!) and path.

from b2biiConversion import convertBelleMdstToBelleIIMdst
convertBelleMdstToBelleIIMdst(inputBelleMDSTFile, path=my_path)

  • inputBelleMDSTFile : a BASF mdst file name or an url of the mdst file location.

  • path=my_path : your basf2 steering process path.

Examples of analysis steering files can be found in example directory of the b2bii package:

ls $BELLE2_RELEASE_DIR/b2bii/examples

Hint

For an introductory lesson, take a look at Section 3.4.11.