#!/usr/bin/env python3
##########################################################################
# basf2 (Belle II Analysis Software Framework) #
# Author: The Belle II Collaboration #
# #
# See git log for contributors and copyright holders. #
# This file is licensed under LGPL-3.0, see LICENSE.md. #
##########################################################################
from variables.utils import create_aliases
import variables
[docs]def mc_gen_topo(n=200):
"""
Gets the list of variables containing the raw topology information of MC generated events.
To be specific, the list including the following variables:
* ``nMCGen``: number of MC generated particles in a given event,
* ``MCGenPDG_i`` (i=0, 1, ... n-2, n-1):
PDG code of the :math:`{\\rm i}^{\\rm th}` MC generated particle in a given event,
* ``MCGenMothIndex_i`` (i=0, 1, ... n-2, n-1):
mother index of the :math:`{\\rm i}^{\\rm th}` MC generated particle in a given event.
.. tip::
* Internally, ``nMCGen``, ``MCGenPDG_i`` and ``MCGenMothIndex_i`` are just aliases of
``nMCParticles``, ``genParticle(i, varForMCGen(PDG))``
and ``genParticle(i, varForMCGen(mcMother(mdstIndex)))``, respectively.
* For more details on the variables, please refer to the documentations of
:b2:var:`nMCParticles`, :b2:var:`genParticle`, :b2:var:`varForMCGen`,
:b2:var:`PDG`, :b2:var:`mcMother`, and :b2:var:`mdstIndex`.
Parameters:
n (int): number of ``MCGenPDG_i``/``MCGenMothIndex_i`` variables. Its default value is 200.
.. note::
* To completely examine the topology information of the events in an MC sample,
the parameter ``n`` should be greater than or equal to the maximum of ``nMCGen`` in the sample.
* Normally, the maximum of ``nMCGen`` in the MC samples at Belle II is less than 200.
Hence, if you have no idea about the maximum of ``nMCGen`` in your own MC sample,
it is usually a safe choice to use the default parameter value 200.
* However, an overlarge parameter value leads to unnecessary waste of disk space and
redundant variables with inelegant ``nan`` values.
Hence, if you know the maximum of ``nMCGen`` in your own MC sample,
it is a better choice to assign the parameter a proper value.
"""
list_of_indexes = [str(i) for i in range(n)]
wrapper = 'genParticle({variable}, varForMCGen(PDG))'
prefix = 'MCGenPDG'
MCGenPDG = create_aliases(list_of_indexes, wrapper, prefix)
wrapper = 'genParticle({variable}, varForMCGen(mcMother(mdstIndex)))'
prefix = 'MCGenMothIndex'
MCGenMothIndex = create_aliases(list_of_indexes, wrapper, prefix)
variables.variables.addAlias('nMCGen', 'nMCParticles')
list_of_variables = ['nMCGen']
for i in range(n):
list_of_variables.append(MCGenPDG[i])
list_of_variables.append(MCGenMothIndex[i])
return list_of_variables
