Belle II Software light-2406-ragdoll
variablesToExtraInfo.py
1#!/usr/bin/env python3
2
3
10
11# The VariablesToExtraInfo module saves variables at some stage in the
12# processing chain for recovery later. In this example it saves the invariant
13# mass of D0 candidates, before- and after- running a vertex fit. You could
14# also use this to save electron energy (or dielectron q2) before- and after-
15# running Bremsstrahlung correction or similar.
16#
17# For full documentation please refer to https://software.belle2.org
18# Anything unclear? Ask questions at https://questions.belle2.org
19
20import basf2
21import modularAnalysis as ma # a shorthand for the analysis tools namespace
22from vertex import kFit
23
24mypath = basf2.Path() # create a new path
25
26# add input data and ParticleLoader modules to the path
27ma.inputMdstList([basf2.find_file('analysis/tests/mdst.root')], path=mypath)
28ma.fillParticleLists([('K-', 'kaonID > 0.2'), ('pi+', 'pionID > 0.2')], path=mypath)
29ma.reconstructDecay('D0 -> K- pi+', '1.750 < M < 1.95', path=mypath)
30ma.matchMCTruth('D0', path=mypath)
31
32# this saves the "pre-vertex fit" mass in the extraInfo() of the D0 particle
33mypath.add_module('VariablesToExtraInfo',
34 particleList='D0',
35 variables={'M': 'M_before_vertex_fit'})
36
37# Now we do a vertex fit (this can change the mass).
38# All candidates are kept.
39kFit('D0', -1.0, path=mypath)
40
41# now save the pre- and post- fit mass using VariablesToNtuple
42mypath.add_module('VariablesToNtuple',
43 particleList='D0',
44 variables=['M', 'extraInfo(M_before_vertex_fit)'])
45
46# It is important to understand that modules are loaded onto a basf2.Path by
47# the modularAnalysis convenience functions (or by hand by you) and the order
48# matters so you need to put VariablesToExtraInfo in the path *before* your
49# processing which may alter variables.
50#
51# Here is an example of how to check this:
52basf2.B2RESULT("Printing modules on the path")
53for i, module in enumerate(mypath.modules()):
54 basf2.B2RESULT(i, " ", module.name())
55# We use B2RESULT because it stands out in amongst the basf2 information.
56# I could use python's native print()
57
58# process the data
59basf2.process(mypath)
60print(basf2.statistics)