8. B2BII

The b2bii package in basf2 converts Belle MDST files (BASF data format) to Belle II MDST (basf2 data format). This enables performing physics analysis using data collected with Belle detector with the analysis software and algorithms developed for the analysis of data collected with the Belle II detector. The B2BII converter allows for estimation and validation of performances of various advanced algorithms being developed for Belle II.

8.1. Overview

The B2BII converter reads and converts Belle MDST within basf2. The converted data is to be analysed within the same job, without any intermediate conversion to output ROOT file (Belle II MDST format). The B2BII conversion plus analysis workflow is illustrated in this figure:

../../_images/B2BIIWorkFlow_update_v2.png

and is divided between

Conversion modules:

  • B2BIIMdstInput: opens and reads Belle MDST file,

  • B2BIIFixMdst: performs correction to Belle MDST data before the conversion is performed,

  • B2BIIConvertMdst: performs Belle mdst to Belle II mdst conversion. After this final step the DataStore is filled with Belle II-type MDST dataobjects (Tracks, ECLClusters, PIDLikelihhoods,…).

basf2 analysis:

  • This part contains the usual sequence of basf2 physics analysis modules.

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.

8.3. Converted data objects and other information

This section briefly describes what is converted, in what way, and how the converted objects should be used in the analysis.

8.4. Belle MDST samples

The most important argument in convertBelleMdstToBelleIIMdst function is the first one, specifying the input Belle MDST sample to be converted and analysed. You can either specify the location of the input Belle MDST file (e.g. when running over your privately produced signal MC):

convertBelleMdstToBelleIIMdst('/location_to_my_mdst_files/myMDSTFile.mdst', path=mypath)

or specify the url of real data or generic MC samples. For example:

convertBelleMdstToBelleIIMdst('http://bweb3/montecarlo.php?ex=37&rs=100&re=200&ty=evtgen-mixed&dt=on_resonance&bl=caseB&st=0', path=mypath)

The form of the url is the same as used in BASF. More information is available at the Belle analysis software page.

Note

Belle index files cannot be used in the conversion, please use HadronB(J) skim files, or convert your index files to mdst files first and then perform b2bii conversion.

There are different kind of MC/data samples available at Belle.

8.5. FAQ

8.6. b2bii functions