Belle II Software light-2406-ragdoll
B2A400-TreeFit.py
1#!/usr/bin/env python3
2
3
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11
34
35import basf2 as b2
36import modularAnalysis as ma
37import vertex as vx
38from stdPi0s import stdPi0s
39
40# create path
41my_path = b2.create_path()
42
43# load input ROOT file
44ma.inputMdst(filename=b2.find_file('B02D0pi0_D02pi0pi0.root', 'examples', False),
45 path=my_path)
46
47
48# use standard final state particle lists
49#
50# creates "pi0:eff40_May2020Fit" ParticleList
51# see Standard Particles section at https://software.belle2.org/
52stdPi0s(listtype='eff40_May2020Fit', path=my_path)
53
54# reconstruct D0 -> pi0 pi0 decay
55# keep only candidates with 1.7 < M(pi0pi0) < 2.0 GeV
56ma.reconstructDecay(decayString='D0:pi0pi0 -> pi0:eff40_May2020Fit pi0:eff40_May2020Fit',
57 cut='1.7 < M < 2.0',
58 path=my_path)
59
60# reconstruct B0 -> D0 pi0 decay
61# keep only candidates with Mbc > 5.24 GeV
62# and -1 < Delta E < 1 GeV
63ma.reconstructDecay(decayString='B0:all -> D0:pi0pi0 pi0:eff40_May2020Fit',
64 cut='5.24 < Mbc < 5.29 and abs(deltaE) < 1.0',
65 path=my_path)
66
67# perform MC matching (MC truth association)
68ma.matchMCTruth(list_name='B0:all', path=my_path)
69
70vx.treeFit(list_name='B0:all',
71 conf_level=0, # 0:keep only fit survivors, -1: keep all candidates; optimise this cut for your need
72 ipConstraint=True,
73 # pins the B0 PRODUCTION vertex to the IP (increases SIG and BKG rejection) use for better vertex resolution
74 updateAllDaughters=True, # update momenta of ALL particles
75 massConstraint=['pi0'], # mass constrain ALL pi0
76 path=my_path)
77
78# whatever you are interested in
79#
80# see analysis/VariableManager/ for implementation of the vars
81variables = [
82 'isSignal', # MC truth
83 'chiProb', # pValue of the fit use this in your analysis to reject background
84 "p", # momentum (of the B0)
85 "mcP", # generated momentum
86 "pErr", # momentum uncertainty taking the full px, py, pz covariance into account
87
88 "daughter(0, E)", # momentum of the D0 that is updated if updateAllDaughters=True.
89 "originalDaughter(0, E)", # momentum of the original D0.
90]
91
92# safe the output
93output_name = "B2A400-TreeFit.root"
94my_path.add_module('VariablesToNtuple',
95 treeName='B0',
96 particleList='B0:all',
97 variables=variables,
98 fileName=output_name)
99
100# Process the events
101b2.process(my_path)
102
103# print out the summary
104print(b2.statistics)