## 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.
Standard Pol3 fit fails in presence of a dead tube
If a fit returns a bad chi**2 value then the method scans
Pol3 fit succeeds if the tube is removed from the fit
Pol3 + gap describes well a dead tube
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.

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){

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

```

-- BaroncelliToni - 21 Nov 2008

Topic attachments
I Attachment History Action Size Date Who Comment
gif BMF2C14_83845_map.gif r1 manage 17.6 K 2008-11-21 - 12:06 BaroncelliToni
gif deadtube1.gif r1 manage 8.4 K 2009-04-17 - 17:20 BaroncelliToni
gif deadtube2.gif r1 manage 9.0 K 2009-04-17 - 17:23 BaroncelliToni
gif deadtube6.gif r1 manage 8.7 K 2009-04-17 - 17:49 BaroncelliToni
gif deadtubepol3fail.gif r1 manage 8.3 K 2009-04-17 - 18:19 BaroncelliToni
gif deadtubepol3ok.gif r1 manage 8.7 K 2009-04-17 - 18:20 BaroncelliToni
Topic revision: r7 - 2020-08-19 - TWikiAdminUser

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