plot_LL_diff.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
 
 
 
from basf2 import *
 
from ROOT import Belle2
from ROOT import TH1F, TH2F, TCanvas
 
# the histograms to fill
hist = [TH2F(
    'hist' + str(i),
    'hist' + str(i),
    50,
    0.0,
    3.5,
    50,
    -100,
    100,
) for i in range(4)]
 
hist[0].SetTitle('True pions, dE/dx')
hist[1].SetTitle('True kaons, dE/dx')
hist[2].SetTitle('True pions, TOP')
hist[3].SetTitle('True kaons, TOP')
 
# define the python module to extract and plot PID information
 
 
class MinModule(Module):
 
    """
    Get LL differences from PIDLikelihood and fill them into histograms
    """
 
    def __init__(self):
        """
        call constructor of base class, required.
        """
 
        super(MinModule, self).__init__()
 
    def event(self):
        """
        reimplement Module::event()
        """
 
        pids = Belle2.PyStoreArray('PIDLikelihoods')
        for pid in pids:
            track = pid.getRelatedFrom('Tracks')
            if track:
                mcpart = track.getRelatedTo('MCParticles')
            if not track or not mcpart:
                # some tracks don't have an mcparticle
                B2WARNING('problems with track <-> mcparticle relations')
                event = Belle2.PyStoreObj('EventMetaData').obj().getEvent()
                print('event: %d, track: %d' % (event, track.getArrayIndex()))
            else:
                pdg = abs(mcpart.getPDG())
                momentumVec = mcpart.getMomentum()
                momentum = momentumVec.Mag()
                if momentum > 3.5:  # cut off
                    continue
                theta = momentumVec.CosTheta()
 
                # particle to compare with pions
                selectedpart = Belle2.Const.kaon
                pid_dedx = Belle2.Const.PIDDetectorSet(Belle2.Const.CDC)
                pid_top = Belle2.Const.PIDDetectorSet(Belle2.Const.TOP)
                logl_sel = pid.getLogL(selectedpart, pid_dedx)
                logl_pi = pid.getLogL(Belle2.Const.pion, pid_dedx)
                dedx_DLL = logl_pi - logl_sel
 
                logl_sel = pid.getLogL(selectedpart, pid_top)
                logl_pi = pid.getLogL(Belle2.Const.pion, pid_top)
                top_DLL = logl_pi - logl_sel
 
                if pdg == selectedpart.getPDGCode():
                    hist[0].Fill(momentum, dedx_DLL)
                    hist[2].Fill(momentum, top_DLL)
                elif pdg == 211:
                    hist[1].Fill(momentum, dedx_DLL)
                    hist[3].Fill(momentum, top_DLL)
 
    def terminate(self):
        """
        Draw histograms on canvas and save image.
        """
 
        c1 = TCanvas('c', 'c', 800, 600)
        c1.Divide(2, 2)
        c1.Show()
        for i in range(4):
            c1.cd(i + 1)
            hist[i].Draw('colz')
        # c1.Draw()
 
        c1.SaveAs('ll_diff.png')
        print('Output plots saved in ll_diff.png')
 
 
# create path
main = create_path()
 
# define number of events
eventinfosetter = register_module('EventInfoSetter')
eventinfosetter.param('evtNumList', [20])
main.add_module(eventinfosetter)
main.add_module('EvtGenInput')
 
# do full simulation and reconstruction
from simulation import add_simulation
from reconstruction import add_reconstruction
add_simulation(main)
add_reconstruction(main)
 
# draw histograms of log likelihood differences
main.add_module(MinModule())
 
# process events and print call statistics
process(main)
print(statistics)