Gate

last modified: 2024-01-17 by Kodai Okawa

It is very important to select events for online analysis as well. There are several options to do so, and I will cover all of them. If you know other useful way, please let me know.

Histogram definition
TCutG object
TGateStopProcessor

For clearer understanding, we will use this figure, and we call this as default figure:

Histogram definition

We explained in the Histograms page, but again we describe about histogram definition focus on the cut part.

The default figure defined like this:

anchor:
  - &f2ppacx ["f2ppac.fX",200,-50.,50.]
  - &f2ppacy ["f2ppac.fY",200,-50.,50.]
alias:
group:
  - name: f2check
    title: f2_check
    contents:
      - name: f2PPAC X vs Y
        title: f2ppac X vs Y
        x: *f2ppacx
        y: *f2ppacy

For example, let’s add the gate to select only “-10.0 < X < 10.0”. We can use alias node to define that.

anchor:
  - &f2ppacx ["f2ppac.fX",200,-50.,50.]
  - &f2ppacy ["f2ppac.fY",200,-50.,50.]
alias:
  centerx: abs(f2ppac.fX) < 10.0;
group:
  - name: f2check
    title: f2_check
    contents:
      - name: f2PPAC X vs Y{centerx}
        title: f2ppac X vs Y{centerx}
        x: *f2ppacx
        y: *f2ppacy
        cut: centerx

Then the following histogram is created.

Also, multiple conditions can be specified at the same time.

anchor:
  - &f2ppacx ["f2ppac.fX",200,-50.,50.]
  - &f2ppacy ["f2ppac.fY",200,-50.,50.]
alias:
  centerx: abs(f2ppac.fX) < 10.0;
  centery: abs(f2ppac.fY) < 10.0;
group:
  - name: f2check
    title: f2_check
    contents:
      - name: f2PPAC X vs Y{centerx && centery}
        title: f2ppac X vs Y{centerx && centery}
        x: *f2ppacx
        y: *f2ppacy
        cut: centerx && centery

TCutG object

We can also use TCutG object to select the event. As in new commands page, let’s assume we create this TCutG ROOT file by tcutg command. And the ROOT file and TCutG object name is f2star.

If you want to use this object to select event, just add this line is fine, as long as you use userlogon.C.

anchor:
  - &f2ppacx ["f2ppac.fX",200,-50.,50.]
  - &f2ppacy ["f2ppac.fY",200,-50.,50.]
alias:
group:
  - name: f2check
    title: f2_check
    contents:
      - name: f2PPAC X vs Y{f2star}
        title: f2ppac X vs Y{f2star}
        x: *f2ppacx
        y: *f2ppacy
        cut: f2star

Of course we can use in “tree->Draw()” because this TCutG objects are automatically loaded. The following sentence generate the same figure.

artemis [] fcd 0
artemis [] zo
artemis [] tree->Draw("f2ppac.fY:f2ppac.fX>>(200,-50.,50., 200,-50.,50.)","f2star","colz")

TGateStopProcessor

The method used until now was to process just histograms and analyze them for all events in the event loop. If you know which events you don’t want, there are processors that allow you to skip the event loop under certain conditions. This may speed up the event loop.

For example. when we want to analyze only beam single event (it means the events are not coincident with SSD, and let’s suppose that condition is given by single.fID==0), let’s prepare the steering file.

Processor:
  - name: proc_gateinit
    type: art::TGateArrayInitializer
    parameter:
      OutputTransparency: 1

  - name: proc_gate
    type: art::TTreeFormulaGateProcessor
    parameter:
      Definitions:
        - "beam_single; single.fID==0"
      OutputTransparency: 1
      Verbose: 1

  - name: beam_single_gate
    type: art::TGateStopProcessor
    parameter:
      GateName: beam_single
      OutputTransparency: 1
      StopIf: 0
      Verbose: 1

To use TGateStopProcessor, we need to initialize the “gate” array object, so the first art::TGateArrayInitializer is needed. In the second processor, art::TTreeFormulaGateProcessor, we define the gate condition.

Then the art::TGateStopProcessor judges the event is skipped or not. In the case of StopIf: 0, artemis ignore the event that the condition become false. In other words, StopIf: 0 means artemis will analyze the event only when the condition is true.

Then, including this yaml file to the main steering file, you can check only the selected events.

Anchor:
  - &input ridf/@NAME@@NUM@.ridf
  - &output output/@NAME@/@NUM@/hoge@NAME@@NUM@.root
  - &histout output/@NAME@/@NUM@/hoge@NAME@@NUM@.hist.root

Processor:
  - name: timer
    type: art::TTimerProcessor

  - name: ridf
    type: art::TRIDFEventStore
    parameter:
      OutputTransparency: 1
      InputFiles:
        - *input
      SHMID: 0

  - name: mapper
    type: art::TMappingProcessor
    parameter:
      OutputTransparency: 1

# include some other steering files

  - include: gate/coin.yaml

  - name: outputtree
    type: art::TOutputTreeProcessor
    parameter:
      FileName:
        - *output

Info

We didn’t check if we can use the TCutG object in this process…