8.4.1. Belle Data and Generic MC

Generic MC is the official MC samples at Belle, which was generated with run-dependent beam background. There are multiple streams of these samples, and each stream contains the same amount of events as present in the real Belle data.

There are several different categories of Belle MC: - Generic \(B\) samples : charged (\(B^+ B^-\)) and mixed (\(B^{0}\bar{B}^{0}\)) - Continuum samples : uds, charm - Y(5S) samples : bsbs, nonbsbs

Generic \(B\) samples only contain decay modes with \(b \to c\) quark transitions, and have been generated based on the decay tables at

/sw/belle/belle/b20090127_0910/share/data-files/evtgenutil/DECAY.DEC.

How to find Generic MC and data samples?

You can find the sample(s) you want through Belle File Search Engine

Warning

Belle File Search Engine is only accessible within KEK domain or via VPN. Or look in the SSH - Secure Shell tutorial for a way to access it via SSH forwarding.

The Belle File Search Engine

Fig. 8.1 The Belle File Search Engine

By specifying Exp No, Event Type, Data Type, and Stream No, Event Type means different MC types (charged, mixed, uds, .. ). Data Type is for different energy runs (on-resonance, off-resonance, …). In total there are 10 streams of Generic \(B\) samples and 6 streams of continuum samples.

You can either use the file list (physical path) or URL as input file list for b2bii jobs.

See also

More information about official MC and data can be found here

8.4.2. Rare B MC

Just from this name you can guess that this type of MC aims for rarer processes, such as \(b \to u \ell \nu\), \(e^+ e^- \to \tau^+ \tau^-\)…

Rare \(B\) MC was generated with an experiment-dependent beam energy, but not run-dependent (i.e. The same beam energy and IP profile in the same experiment).

The location of those special MC files can be found here.

8.4.3. Generating MC sample

There are two parts when generating a MC sample:

  1. evtgen generation

  2. Geant3-based detector simulation

Users can choose between basf or B2BII to generate a set of signal MC for one’s analysis.

Generating signal MC with basf

The mcproduzh package has been used to generate signal MC in Belle for many years. This package was developed by Ushiroda-san, A. Zupanc, and Horii-san, and it consists of generation, simulation, and reconstruction based on evtgen and gsim scripts (gsim is Belle slang for the simulated detector response that results from the use of Geant3 within the Belle analysis software framework basf – the output of gsim scripts are Belle mdst files).

It will create MC samples for a list of experiments, normalized by their \(N(B\bar{B})\) or integrated luminosity.

The beam energy, IP profile, and detector configuration of this MC will be experiment-dependent, but not run-dependent. Moreover, RunNo for these events will be set to 0 in the mcproduzh package, hence it doesn’t work for off-resonance or \(\Upsilon(nS)\).

See also

More information of generating Belle MC in basf can be found here

Generating signal MC with B2BII

Signal MC samples can also be generated in basf2, using the BelleMCOutput module. An example script of how to generate a MC sample with BelleMCOutput is at

ls $BELLE2_RELEASE_DIR/b2bii/examples/BelleMCGeneration.py

Here are several notes while using BelleMCOutput.

Beam energy for MC generation

The default global tag for MC generation is set to be the default gt for MC jobs, B2BII_MC. The beam energy spread is not considered when the payloads were created from the Belle DB; therefore, if you would like to include the energy spread in MC generation, please modify the prepended global tag: b2bii_beamParameters_with_smearing.

# Use B2BII global tag.
basf2.conditions.prepend_globaltag('b2bii_beamParameters_with_smearing')

Warning

To generate run-independent MC, one must use B2BII_MC for now.

Run dependent MC

If you like to generate run-dependent beam energy MC for non-\(\Upsilon(4S)\) analysis, please contact conveners of your physics subgroup at Belle to get more information regarding the list of runs for your analysis.

Then modify the following line in your generation script:

# Generate for experiment 55, run 402 (run-dependent MC).
main.add_module('EventInfoSetter', expList=55, runList=402, evtNumList=100)

This will generate signal MC using the beam energy from run 402 in experiment 55.

User signal decay files

To generate user-defined decay files (aka signal decay files), use the following line in the script:

from generators import add_evtgen_generator
add_evtgen_generator(path=mypath,
                     finalstate="signal",
                     signaldecfile="user_defined_decfile.dec"
)

Note

Because the Belle detector geometry is not and will not be implemented in basf2, the simulation part can only be done in basf.