Access MC-truth information in Bender
As it was mentioned above, the processing of simulation data in Bender is rather simple, one just needs to inherit the algorithm from base class AlgoMC, this class can be imported from the Bender.MainMC module.
from Bender.MainMC import * # it imports also the whole content of Bender.Main module
class MyAlg(AlgoMC) : ...
And the corresponding wrapper for Selection-framework is BenderMCSelection
Get MC-truth data
To access to MC-truth data one uses the method mcselect, that is very similar to the method select discussed above
mcB = self.mcselect ( 'mcB' , '[Beauty ==> J/psi(1S) K+ K-]CC' )
mcK = self.mcselect ( 'mcK' , '[Beauty ==> J/psi(1S) ^K+ ^K-]CC' ) ## note marked components
mcb = self.mcselect ( 'mcb' , BEAUTY ) ## any beauty hadron
mc0 = self.mcselect ( 'mc0' , 'B0' == MCABSID ) ## B0 or B~0
Again, as selection criteria one can use the decay descriptors or LoKi MC-functors.
dv = DaVinci ( Simulation = True , ... )
bsel = BenderMCSelection ( 'MCtruth' , [] ) ## <--- HERE!
daVinci.UserAlgorithms.append ( bsel )
Challenge
Try to code some MC-truth algorithm, that get some true MC-decays, and fill simple n-tuple/tree with some simple kinematical information on some of decay products. Try to select as an example the ordinary ALLSTREAMS.DST (not Turbo version!). Processing of ALLSTREAMS.DST/Turbo and various kinds of ALLSTREAMS.MDST and MC-Turbo requires a bit different configurtaion steos, that we'll discuss later. For a time being y ou can use e.g. the MC-file '/lhcb/MC/2012/ALLSTREAMS.DST/00033494/0000/00033494_00000013_1.allstreams.dst', that contains the true MC-decays Bs -> J/psi K+ K- pi+ pi- with many intermediate resonances.
Solution
The complete module, that processes the events of [B_s0 ==> J/psi(1S) K+ K- pi+ pi-]CC with very rich structure of intermediate resonances is available here