Atlas MDT Dead Elements Analysis

The search for dead elements in a MDT chamber is handled by the code described in this page. Dead elements are searched for in order of decreasing complexity (multi-layers, layers, mezzanines, tubes).

The algorithm

The basic idea of the algorithm is that the hit map of a MDT layer is smooth and is normally well described by a polynomial of low degree (say 3rd degree). A dead tube would result in a fit failure. Thus the first step of the algorithm is trying to fit a (portion of a) layer with a Pol3 function. A bad chi**2 would be a first indication of a dead tube. See below a failing fit due to the presence of a dead tube. Before trying a fit procedure the error of a '0 content' bin is set to 2.3 because fitters normally discard bins with 0 statistical error. If a fit returns a bad chi**2 value then the method scans The I/O dialogue is realised by using three different histograms:

• idh1 contains the hit map of a MDT chamber. There is one bin for each channel including cut-outs. The hit map is created using hits which pass an cut of 100 adc counts to limit the presence of noisy channels;
• idh2 contains the structure of the chamber (see below) and tells where different layers/multi layers start/end. It also contains the information of known dead tubes;
• idh3 is a modification of idh2 described before. Every time one dead tube (or a sequence of dead tubes) is found the corrisponding bin (bins) are modified according to table below.

MDTDeadElementsAnalysis::deadElementsAnalysis(TH1F* idh1, TH1F* HRef, TH1F* deadTubesMap, int nlayers_ml, string chambname)

Dead Multi Layers	Dead Layers	Dead Mezzanines	Dead Tubes
bin + signML*5	bin + signML*4	bin + signML*3	bin + signML*2

Structure of MDT Dead Elements Analysis is listed below

void MDTDeadElementsAnalysis::deadElementsAnalysis(TH1F* idh1, TH1F* HRef, TH1F* deadTubesMap, int nlayers_ml, string chambname){

  MDTDeadElementsAnalysis mdtTubeAna = new MDTDeadElementsAnalysis;
  mdtTubeAna->getBasicGeometry(HRef,nlayers_ml,chambname);
  // CLEAR ALL Lists :
  mdtTubeAna->ClearList();
  int total_bins= (int) idh1->GetNbinsX();
  mdtTubeAna->Clear(total_bins);
  mdtTubeAna->deadChambers(idh1,HRef, deadTubesMap, chambname);
  mdtTubeAna->deadMultilayers(idh1,HRef, deadTubesMap, chambname);
  mdtTubeAna->deadLayers(idh1,HRef, deadTubesMap, chambname);
  mdtTubeAna->deadMezzanines(idh1,HRef, deadTubesMap, chambname);
  mdtTubeAna->deadTubes(idh1,HRef, deadTubesMap, chambname);
  if(verbose) mdtTubeAna->printSummary() ;
  if(writeResultsToAsciFile){
    cout<<" Writing to Asci File "<printSummaryToAsciFile() ;}
  if(verbose) deadTubesMap->Draw();

}// deadElementsAnalysis

Dead Chambers

Dead Multi Layers

Dead Layers

Dead Mezzanines

Dead Tubes

-- BaroncelliToni - 21 Nov 2008