This example creates a simple selection for J/psi → mu+ mu- using the Particle Selection Framework (i.e. CombineParticle). It is a simplified version of the algorithm described in DaVinciTutorial4.

• login to lxplus
• make sure you have a Grid-Certificate

myOptions.py

from Gaudi.Configuration import *                                          
from GaudiKernel.SystemOfUnits import MeV, GeV
from Configurables import CombineParticles
from PhysSelPython.Wrappers import Selection, SelectionSequence, DataOnDemand
 
# prepare input data
_muons = DataOnDemand('_stdLooseMuons', Location = 'StdLooseMuons')
 
# create algorithm
myalg = CombineParticles("myalg")
 
# define decay and cuts
myalg.DecayDescriptor = "J/psi(1S) -> mu+ mu-"
myalg.CombinationCut = "ADAMASS('J/psi(1S)')<30*MeV"
myalg.MotherCut = "(VFASPF(VCHI2/VDOF)<10)"
 
# add plots to algorithm
from Configurables import LoKi__Hybrid__PlotTool as PlotTool
myalg.HistoProduce = True
myalg.addTool ( PlotTool ( 'DaughtersPlots' ) )
myalg.DaughtersPlots.Histos = {
   'P'  : ('momentum' , 0*GeV ,30*GeV) ,
   'M'  : ('mass'     ,0*GeV,1*GeV)
   }
myalg.addTool( PlotTool ( "MotherPlots" ) )
myalg.MotherPlots.Histos = {
   "P"  : ('momentum',0*GeV,100*GeV) ,
   "M"  : ('mass',0*GeV,4*GeV)
   }
 
# create selection
# Selection needs to be defined after all changes to the Algorithm
LooseJpsi2MuMu = Selection("seqLooseJPsi2MuMu", Algorithm = myalg, RequiredSelections =[ _muons ])
 
# start selection sequence
mySeq = SelectionSequence("mySeq", TopSelection = LooseJpsi2MuMu)
 
# configure the application.
from Configurables import DaVinci
DaVinci().UserAlgorithms = [ mySeq.sequence() ]
DaVinci().HistogramFile  = "histograms.root"    # Histogram file
DaVinci().EvtMax         = 1000                  # Number of events to loop over
DaVinci().DataType       = "MC09"               # Default anyway
DaVinci().Simulation     = True                 # It's MC

For more details about the names used in the DecayDescriptor, look at the ParticleTable. For a list of availbale funtors for CombinationCut and MotherCut, check the Loki references.

• Set environment for Ganga

SetupProject Ganga

• maybe you need to create a new config file

ganga -g

• start

ganga

• prepare job

t = JobTemplate( application = DaVinci( ))
t.application.optsfile = File( "~/example/myOptions.py" )

• add input data

t.inputdata = browseBK()
# select MC / MC09 / Beam5TeV-VeloClosed-MagDown-Nu1 / MC09-Sim03Reco02-withTruth / 24142000 / DST
# you could instead use an python option file with the data locations 
# (see below on how to generate one)
#t.application.optsfile.append(  File( "~/example/myOptions.py" )  )
# the Ganga-Manual marks this as depreciated

• create a job and run it

j = Job( t, backend = Interactive() )
j.submit()

• run the Bookkeeping-GUI

lhcb_bkk

• select

MC / MC09 / Beam5TeV-VeloClosed-MagDown-Nu1 / MC09-Sim03Reco02-withTruth / 24142000 / DST

• double-click on Nb of Files/Events and select all files

• click Advanced Save
• give Filename (e.g. “myFiles.py”), select PFN(s) and CERN
• click save

SetupProject DaVinci
gaudirun.py myOptions.py myFiles.py

The Algorithm creates a file called histograms.root.

• If run with gaudirun.py it should be in the working directory.
• If run with ganga it can be found at ~/gangadir/workspace/<username>/LocalAMGA/<jobNr>/output/

Start root and have a look at the histograms.

You can find more info at following locations:

• Ganga
• DaVinci