About Object Selection, Overlap Removal and Event Selection cuts and how particles and events are flagged


  • Q: In my Steering File I defined two channels which are orthogonal with respect to each other. How can a single electron be marked in the same time for channel "3j1lepMediumCutsMTSmaller100GeV" and "3j1lepMediumCutsMTBigger100GeV"? The MT is calculated and it cannot be in the same time smaller than 100 GeV and greater than 100 GeV. I thought that MT is unique for one event...


Answer:

Yes, it's true: the MT is unique and it cannot be < 100 and > 100 at the same time! smile

But what you find in the name of the channel, "MTSmaller100", in this case refers to "EVENT SELECTION".

And the channel name is, of course, only a name. You can name it "DonaldDuck" or "Goofy" wink It's not related to the specific event selection.

A single channel is just a container of definitions, where you can change or define:

1) object selction and overlap removal cuts 2) event selection cuts

Only EVENTS are flagged on the base of event selection. The flags for events are stored in the "channels" branch. And of course you won't find a single event belonging to both of those channels you mentioned above. As the event selection cuts of those two channels are orthogonal.

But particles, like electrons, are not flagged on the base of event selection. They are flagged on the base of "object selection and overlap removal" cuts defined in a channel.

Default values for object selection and overlap removal cuts are those CSC-style defined in SUSYTools/src/SUSYDefinitions.cxx. For example the default pt() cut for electron selection is 10GeV: so an electron is considered a "good electron" if its pt() is > 10GeV. And all electrons passing those default CSC values will be flagged as "DEFAULT".

Moreover in the steering file you can change the default object selection and overlap cuts, editing the field customCuts, and particles will be flagged according to those new cuts.

Let's continue our example with the electron.

Let'ssay that in our steering file we define five channels/analyses:

'3j1lepMediumCutsMTBigger100GeV':{'channel': 'ljjj',
                                              'cuts': {'1': {'label': 'leptonPtCutsExclusive',
                                                             'value': [20*Units.GeV]
                                                             },
                                                       '2': {'label': 'electronPtVeto',
                                                             'range': [10*Units.GeV,20*Units.GeV]
                                                             },
                                                       '3': {'label': 'muonPtVeto',
                                                             'range': [10*Units.GeV,20*Units.GeV]
                                                             },
                                                       '4': {'label': 'jetPtCuts',
                                                             'value': [100*Units.GeV, 40*Units.GeV, 40*Units.GeV],
                                                             },
                                                       '5': {'label': 'missingEtCut',
                                                             'value': 80*Units.GeV,
                                                             },
                                                       '6': {'label': 'METFractionMeffCut',
                                                             'value': 0.25
                                                             },
                                                       '7': {'label': 'sphericityCutCSC',
                                                             'value': 0.2,
                                                             },
                                                       '8': {'label': 'jet_metDPhiCuts',
                                                             'value': [0.2, 0.2, 0.2],
                                                             },
                                                       '9': {'label': 'transverseMassCut',
                                                             'value': 100*Units.GeV,
                                                             'compare': '<='
                                                             },
                                                       },
                                              'customCuts':{'muon':{'ptMin': 20.*Units.GeV},
                                                            'electron':{'ptMin': 20.*Units.GeV},
                                                            },
                                              },
                                              
'3j1lepMediumCutsMTSmaller100GeV':{'channel': 'ljjj',
                                               'cuts': {'1': {'label': 'leptonPtCutsExclusive',
                                                              'value': [20*Units.GeV]
                                                              },
                                                        '2': {'label': 'electronPtVeto',
                                                              'range': [10*Units.GeV,20*Units.GeV]
                                                              },
                                                        '3': {'label': 'muonPtVeto',
                                                              'range': [10*Units.GeV,20*Units.GeV]
                                                              },
                                                        '4': {'label': 'jetPtCuts',
                                                              'value': [100*Units.GeV, 40*Units.GeV, 40*Units.GeV],
                                                              },
                                                        '5': {'label': 'missingEtCut',
                                                              'value': 80*Units.GeV,
                                                              },
                                                        '6': {'label': 'METFractionMeffCut',
                                                              'value': 0.25
                                                              },
                                                        '7': {'label': 'sphericityCutCSC',
                                                              'value': 0.2,
                                                              },
                                                        '8': {'label': 'jet_metDPhiCuts',
                                                                'value': [0.2, 0.2, 0.2],
                                                              },
                                                        '9': {'label': 'transverseMassCut',
                                                              'value': 100*Units.GeV,
                                                              'compare': '>'
                                                              },
                                                        },
                                              'customCuts':{'muon':{'ptMin': 20.*Units.GeV},
                                                                   'electron':{'ptMin': 20.*Units.GeV},
                                                                  },
                                              },
'1lep': {'channel': 'l',
           'cuts': {'1': {'label': 'leptonPtCuts',
                              'value': [20*Units.GeV],
                             },
                      },
           'customCuts': {'muon':{'ptMin': 1.*Units.GeV},
                                  'electron':{'ptMin': 1.*Units.GeV},
                                 },
          },
'1lepDefCut': {'channel': 'l',
                     'cuts': {'1': {'label': 'leptonPtCuts',
                                        'value': [20*Units.GeV],
                                       },
                    },
'TestOnlyJets': {'channel': 'jjj',
                       'cuts': { '1':{'label': 'electronPtVeto',
                                          'range': [20.*Units.GeV, 50.*Units.GeV],
                                          'compare': ['<=','>='],
                                         },
                                  },
                       },
}

Let's take a look at those channels.

As you can see, the first two channels have the same "object selection and overlap" cuts. Because they defined:

'customCuts':{'muon':{'ptMin': 20.*Units.GeV},
                     'electron':{'ptMin': 20.*Units.GeV},
                    },
which means that they take all the standard CSC cuts (the cuts defined in SUSYTools/src/SUSYDefinitions.cxx) but they change the pt() cut for electron and muon, from the default value of 10GeV to the new value of 20GeV.

So those two channels have the SAME OBJECT SELECTION. And thus an electron satisfying the selection of one of those channels, it satisfies the other as well.

But let's continue to look at the channels above.

The "1Lep" channel redefines the pt() cut for electrons and muons as well, from the default value of 10GeV to the new value of 1GeV (for example because this channel is used for performance studies). Thus every electron with pt() > 1GeV, and passing all the other default obejct selection cuts, will be considered as having passed the selection defined in this "1Lep" channel. But, of course, it will not passed the selection of the first two channels, if its pt() won't be > 20GeV.

As you can see in the code above, the two last channels have no "customCuts" defined, that means that they use the Default SUSY CSC obj selection and overlap cuts specified in SUSYTools/src/SUSYDefininitions.cxx.

Hence electrons satifying the object selection and overlap removal cuts for the first two channels will be flagged as "3j1lepMediumCutsMTBigger100GeV" AND (because they have the SAME object selection and overlap cuts) "3j1lepMediumCutsMTSmaller100GeV"; those satisfying the object selection and overlap removal cuts for the third channel will be flagged as "1Lep"; as electrons satisfying the object selection and overlap removal cuts for the fourth and fifth channels (which use the SUSYDefault CSC cuts) will be flagged as "DEFAULT".

A real example now:

  • an electron with pt()= 5 GeV will belong ONLY to the particle list of the "1Lep" channel, because it passes ONLY the selection for that channel (pt()>1GeV). So it will be flagged ONLY "1Lep".
And jets overlapping with it will be removed ONLY for THAT channel, and they will be NOT flagged "1Lep", of course. But the same electron will not pass the selection for other channels, so it will be not part of the particle list for the other channels, and so jets overlapping with it will be not removed for oher channels...simply because that electron does not "exist" for the other channels! wink

  • an electron with pt()=15 GeV will be flagged as "1Lep", "1LepDef" and "DEFAULT". Same considerations as in the previous example for overlapping jets.

  • an electron with pt()=25 GeV will be flagged for ALL our
channels. And jets overlapping with it they will be removed from the particle lists of ALL channels.

So, the name of a channel is just a flag: as I wrote above you can name it "DonaldDuck" or "Goofy" wink It's not related to the specific event selection or object selection. A channel is just a container of:

1) object selction and overlap removal cuts 2) event selection cuts

If a PARTICLE satisfies the Object Selection and Overlap Removal cuts defined in one channel, it will be flagged with the name of that channel (stored in "electronChannels" branch of the output D3PD TTree,e.g.).

If an EVENT satisfies the Event Selection defined in one channel, the event will be flagged with the name of that channel (stored in "channels" branch).

-- RiccardoMariaBianchi - 24 Feb 2009

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Topic revision: r1 - 2009-02-24 - RiccardoMariaBianchi
 
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