Adding documentation for ExB calibration (Marian)
[u/mrichter/AliRoot.git] / ITS / AliITSVertexerZ.cxx
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0c6af5c9 1/**************************************************************************
2 * Copyright(c) 1998-2003, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
d531b7a1 15#include "AliITSVertexerZ.h"
0c6af5c9 16#include<TBranch.h>
7299b7a8 17#include<TClonesArray.h>
0c6af5c9 18#include<TH1.h>
d531b7a1 19#include <TString.h>
0c6af5c9 20#include<TTree.h>
308c2f7c 21#include "AliESDVertex.h"
32e63e47 22#include "AliITSgeomTGeo.h"
7d62fb64 23#include "AliITSDetTypeRec.h"
d531b7a1 24#include "AliITSRecPoint.h"
7299b7a8 25#include "AliITSZPoint.h"
0c6af5c9 26
27/////////////////////////////////////////////////////////////////
28// this class implements a fast method to determine
29// the Z coordinate of the primary vertex
30// for p-p collisions it seems to give comparable or better results
31// with respect to what obtained with AliITSVertexerPPZ
32// It can be used successfully with Pb-Pb collisions
33////////////////////////////////////////////////////////////////
34
35ClassImp(AliITSVertexerZ)
36
37
38
39//______________________________________________________________________
8221b41b 40AliITSVertexerZ::AliITSVertexerZ():AliITSVertexer(),
41fFirstL1(0),
42fLastL1(0),
43fFirstL2(0),
44fLastL2(0),
45fDiffPhiMax(0),
8221b41b 46fZFound(0),
47fZsig(0.),
48fZCombc(0),
8221b41b 49fLowLim(0.),
50fHighLim(0.),
51fStepCoarse(0),
8221b41b 52fTolerance(0.),
7299b7a8 53fMaxIter(0),
54fWindowWidth(0) {
0c6af5c9 55 // Default constructor
7299b7a8 56 SetDiffPhiMax();
57 SetFirstLayerModules();
58 SetSecondLayerModules();
59 SetLowLimit();
60 SetHighLimit();
61 SetBinWidthCoarse();
62 SetTolerance();
63 SetPPsetting();
6fd990e3 64 ConfigIterations();
7299b7a8 65 SetWindowWidth();
0c6af5c9 66}
67
68//______________________________________________________________________
308c2f7c 69AliITSVertexerZ::AliITSVertexerZ(Float_t x0, Float_t y0):AliITSVertexer(),
8221b41b 70fFirstL1(0),
71fLastL1(0),
72fFirstL2(0),
73fLastL2(0),
74fDiffPhiMax(0),
8221b41b 75fZFound(0),
76fZsig(0.),
77fZCombc(0),
8221b41b 78fLowLim(0.),
79fHighLim(0.),
80fStepCoarse(0),
8221b41b 81fTolerance(0.),
7299b7a8 82fMaxIter(0),
83fWindowWidth(0) {
0c6af5c9 84 // Standard Constructor
85 SetDiffPhiMax();
0c6af5c9 86 SetFirstLayerModules();
87 SetSecondLayerModules();
0c6af5c9 88 SetLowLimit();
89 SetHighLimit();
90 SetBinWidthCoarse();
0c6af5c9 91 SetTolerance();
ecc64c3f 92 SetPPsetting();
6fd990e3 93 ConfigIterations();
7299b7a8 94 SetWindowWidth();
60b9526b 95 SetVtxStart((Double_t)x0,(Double_t)y0,0.);
0c6af5c9 96
97}
98
0c6af5c9 99//______________________________________________________________________
100AliITSVertexerZ::~AliITSVertexerZ() {
ecc64c3f 101 // Destructor
102 delete fZCombc;
0c6af5c9 103}
104
6fd990e3 105//______________________________________________________________________
106void AliITSVertexerZ::ConfigIterations(Int_t noiter,Float_t *ptr){
107 // configure the iterative procedure to gain efficiency for
108 // pp events with very low multiplicity
109 Float_t defaults[5]={0.05,0.1,0.2,0.3,0.5};
110 fMaxIter=noiter;
111 if(noiter>5){
112 Error("ConfigIterations","Maximum number of iterations is 5\n");
113 fMaxIter=5;
114 }
115 for(Int_t j=0;j<5;j++)fPhiDiffIter[j]=defaults[j];
116 if(ptr)for(Int_t j=0;j<fMaxIter;j++)fPhiDiffIter[j]=ptr[j];
117}
118
debb3dde 119//______________________________________________________________________
120Int_t AliITSVertexerZ::GetPeakRegion(TH1F*h, Int_t &binmin, Int_t &binmax) const {
121 // Finds a region around a peak in the Z histogram
122 // Case of 2 peaks is treated
123 Int_t imax=h->GetNbinsX();
124 Float_t maxval=0;
125 Int_t bi1=h->GetMaximumBin();
126 Int_t bi2=0;
127 for(Int_t i=imax;i>=1;i--){
128 if(h->GetBinContent(i)>maxval){
129 maxval=h->GetBinContent(i);
130 bi2=i;
131 }
132 }
133 Int_t npeaks=0;
134
135 if(bi1==bi2){
136 binmin=bi1-3;
137 binmax=bi1+3;
138 npeaks=1;
139 }else{
140 TH1F *copy = new TH1F(*h);
141 copy->SetBinContent(bi1,0.);
142 copy->SetBinContent(bi2,0.);
143 Int_t l1=TMath::Max(bi1-3,1);
144 Int_t l2=TMath::Min(bi1+3,h->GetNbinsX());
145 Float_t cont1=copy->Integral(l1,l2);
146 Int_t ll1=TMath::Max(bi2-3,1);
147 Int_t ll2=TMath::Min(bi2+3,h->GetNbinsX());
148 Float_t cont2=copy->Integral(ll1,ll2);
149 if(cont1>cont2){
150 binmin=l1;
151 binmax=l2;
152 npeaks=1;
153 }
154 if(cont2>cont1){
155 binmin=ll1;
156 binmax=ll2;
157 npeaks=1;
158 }
159 if(cont1==cont2){
160 binmin=l1;
161 binmax=ll2;
162 if(bi2-bi1==1) npeaks=1;
163 else npeaks=2;
164 }
165 delete copy;
166 }
167 return npeaks;
168}
0c6af5c9 169//______________________________________________________________________
308c2f7c 170AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(TTree *itsClusterTree){
d681bb2d 171 // Defines the AliESDVertex for the current event
308c2f7c 172 VertexZFinder(itsClusterTree);
6fd990e3 173 Int_t ntrackl=0;
174 for(Int_t iteraz=0;iteraz<fMaxIter;iteraz++){
175 if(fCurrentVertex) ntrackl=fCurrentVertex->GetNContributors();
176 if(!fCurrentVertex || ntrackl==0 || ntrackl==-1){
177 Float_t diffPhiMaxOrig=fDiffPhiMax;
178 fDiffPhiMax=GetPhiMaxIter(iteraz);
308c2f7c 179 VertexZFinder(itsClusterTree);
6fd990e3 180 fDiffPhiMax=diffPhiMaxOrig;
181 }
182 }
308c2f7c 183 FindMultiplicity(itsClusterTree);
6fd990e3 184 return fCurrentVertex;
185}
186
187//______________________________________________________________________
308c2f7c 188void AliITSVertexerZ::VertexZFinder(TTree *itsClusterTree){
6fd990e3 189 // Defines the AliESDVertex for the current event
0c6af5c9 190 fCurrentVertex = 0;
0c6af5c9 191
308c2f7c 192 TTree *tR = itsClusterTree;
06a7cbee 193 fDetTypeRec->SetTreeAddressR(tR);
0c6af5c9 194 TClonesArray *itsRec = 0;
27167524 195 // lc1 and gc1 are local and global coordinates for layer 1
196 Float_t lc1[3]; for(Int_t ii=0; ii<3; ii++) lc1[ii]=0.;
197 Float_t gc1[3]; for(Int_t ii=0; ii<3; ii++) gc1[ii]=0.;
ecc64c3f 198 // lc2 and gc2 are local and global coordinates for layer 2
0c6af5c9 199 Float_t lc2[3]; for(Int_t ii=0; ii<3; ii++) lc2[ii]=0.;
200 Float_t gc2[3]; for(Int_t ii=0; ii<3; ii++) gc2[ii]=0.;
201
06a7cbee 202 itsRec = fDetTypeRec->RecPoints();
2257f27e 203 TBranch *branch;
00a7cc50 204 branch = tR->GetBranch("ITSRecPoints");
0c6af5c9 205
0c6af5c9 206 Int_t nrpL1 = 0;
207 Int_t nrpL2 = 0;
27167524 208
ecc64c3f 209 // By default fFirstL1=0 and fLastL1=79
0c6af5c9 210 for(Int_t module= fFirstL1; module<=fLastL1;module++){
0c6af5c9 211 branch->GetEvent(module);
212 nrpL1+= itsRec->GetEntries();
06a7cbee 213 fDetTypeRec->ResetRecPoints();
0c6af5c9 214 }
ecc64c3f 215 //By default fFirstL2=80 and fLastL2=239
0c6af5c9 216 for(Int_t module= fFirstL2; module<=fLastL2;module++){
217 branch->GetEvent(module);
218 nrpL2+= itsRec->GetEntries();
06a7cbee 219 fDetTypeRec->ResetRecPoints();
0c6af5c9 220 }
0c6af5c9 221 if(nrpL1 == 0 || nrpL2 == 0){
0c6af5c9 222 ResetHistograms();
6fd990e3 223 fCurrentVertex = new AliESDVertex(0.,5.3,-2);
224 return;
0c6af5c9 225 }
ecc64c3f 226 // Force a coarse bin size of 200 microns if the number of clusters on layer 2
227 // is low
228 if(nrpL2<fPPsetting[0])SetBinWidthCoarse(fPPsetting[1]);
ecc64c3f 229 // By default nbincoarse=(10+10)/0.01=2000
230 Int_t nbincoarse = static_cast<Int_t>((fHighLim-fLowLim)/fStepCoarse);
ecc64c3f 231 if(fZCombc)delete fZCombc;
232 fZCombc = new TH1F("fZCombc","Z",nbincoarse,fLowLim,fLowLim+nbincoarse*fStepCoarse);
7299b7a8 233
27167524 234 /* Test the ffect of mutiple scatternig on error. Negligible
7299b7a8 235 // Multiple scattering
236 Float_t beta=1.,pmed=0.875; //pmed=875 MeV (for tracks with dphi<0.01 rad)
237 Float_t beta2=beta*beta;
238 Float_t p2=pmed*pmed;
239 Float_t rBP=3; //Beam Pipe radius = 3cm
240 Float_t dBP=0.08/35.3; // 800 um of Be
241 Float_t dL1=0.01; //approx. 1% of radiation length
242 Float_t theta2BP=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dBP);
243 Float_t theta2L1=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dL1);
244*/
27167524 245 Int_t maxdim=TMath::Min(nrpL1*nrpL2,50000); // temporary; to limit the size in PbPb
f5f6da22 246 static TClonesArray points("AliITSZPoint",maxdim);
7299b7a8 247 Int_t nopoints =0;
27167524 248 for(Int_t modul1= fFirstL1; modul1<=fLastL1;modul1++){ // Loop on modules of layer 1
8c42830a 249 if(!fUseModule[modul1]) continue;
27167524 250 UShort_t ladder=int(modul1/4)+1; // ladders are numbered starting from 1
251 branch->GetEvent(modul1);
252 Int_t nrecp1 = itsRec->GetEntries();
f5f6da22 253 static TClonesArray prpl1("AliITSRecPoint",nrecp1);
254 prpl1.SetOwner();
27167524 255 for(Int_t j=0;j<nrecp1;j++){
256 AliITSRecPoint *recp = (AliITSRecPoint*)itsRec->At(j);
f5f6da22 257 new(prpl1[j])AliITSRecPoint(*recp);
27167524 258 }
06a7cbee 259 fDetTypeRec->ResetRecPoints();
27167524 260 for(Int_t j1=0;j1<nrecp1;j1++){
f5f6da22 261 AliITSRecPoint *recp = (AliITSRecPoint*)prpl1.At(j1);
32e63e47 262 /*
27167524 263 lc1[0]=recp->GetDetLocalX();
264 lc1[2]=recp->GetDetLocalZ();
265 geom->LtoG(modul1,lc1,gc1);
266 // Global coordinates of this recpoints
32e63e47 267 */
268 recp->GetGlobalXYZ(gc1);
308c2f7c 269 gc1[0]-=GetNominalPos()[0]; // Possible beam offset in the bending plane
270 gc1[1]-=GetNominalPos()[1]; // " "
27167524 271 Float_t r1=TMath::Sqrt(gc1[0]*gc1[0]+gc1[1]*gc1[1]);
272 Float_t phi1 = TMath::ATan2(gc1[1],gc1[0]);
273 if(phi1<0)phi1+=2*TMath::Pi();
274 Float_t zc1=gc1[2];
275 Float_t erz1=recp->GetSigmaZ2();
276 for(Int_t ladl2=0 ; ladl2<fLadOnLay2*2+1;ladl2++){
277 for(Int_t k=0;k<4;k++){
278 Int_t ladmod=fLadders[ladder-1]+ladl2;
32e63e47 279 if(ladmod>AliITSgeomTGeo::GetNLadders(2)) ladmod=ladmod-AliITSgeomTGeo::GetNLadders(2);
280 Int_t modul2=AliITSgeomTGeo::GetModuleIndex(2,ladmod,k+1);
8c42830a 281 if(!fUseModule[modul2]) continue;
27167524 282 branch->GetEvent(modul2);
283 Int_t nrecp2 = itsRec->GetEntries();
284 for(Int_t j2=0;j2<nrecp2;j2++){
285 recp = (AliITSRecPoint*)itsRec->At(j2);
32e63e47 286 /*
27167524 287 lc2[0]=recp->GetDetLocalX();
288 lc2[2]=recp->GetDetLocalZ();
289 geom->LtoG(modul2,lc2,gc2);
32e63e47 290 */
291 recp->GetGlobalXYZ(gc2);
308c2f7c 292 gc2[0]-=GetNominalPos()[0];
293 gc2[1]-=GetNominalPos()[1];
27167524 294 Float_t r2=TMath::Sqrt(gc2[0]*gc2[0]+gc2[1]*gc2[1]);
295 Float_t phi2 = TMath::ATan2(gc2[1],gc2[0]);
296 if(phi2<0)phi2+=2*TMath::Pi();
297 Float_t zc2=gc2[2];
298 Float_t erz2=recp->GetSigmaZ2();
299
300 Float_t diff = TMath::Abs(phi2-phi1);
301 if(diff>TMath::Pi())diff=2.*TMath::Pi()-diff;
302 if(diff<fDiffPhiMax){
303 // Float_t tgth=(zc2[j]-zc1[i])/(r2-r1); // slope (used for multiple scattering)
304 Float_t zr0=(r2*zc1-r1*zc2)/(r2-r1); //Z @ null radius
305 Float_t ezr0q=(r2*r2*erz1+r1*r1*erz2)/(r2-r1)/(r2-r1); //error on Z @ null radius
306 /*
307 // Multiple scattering
7299b7a8 308 ezr0q+=r1*r1*(1+tgth*tgth)*theta2L1/2; // multiple scattering in layer 1
309 ezr0q+=rBP*rBP*(1+tgth*tgth)*theta2BP/2; // multiple scattering in beam pipe
310 */
f5f6da22 311 if(nopoints<maxdim) new(points[nopoints++])AliITSZPoint(zr0,ezr0q);
27167524 312 fZCombc->Fill(zr0);
313 }
314 }
06a7cbee 315 fDetTypeRec->ResetRecPoints();
27167524 316 }
0c6af5c9 317 }
318 }
f5f6da22 319 prpl1.Clear();
0c6af5c9 320 }
7299b7a8 321
f5f6da22 322 points.Sort();
7299b7a8 323
6fd990e3 324 Double_t contents = fZCombc->GetEntries()- fZCombc->GetBinContent(0)-fZCombc->GetBinContent(nbincoarse+1);
325 if(contents<1.){
326 // Warning("FindVertexForCurrentEvent","Insufficient number of rec. points\n");
0c6af5c9 327 ResetHistograms();
6fd990e3 328 fCurrentVertex = new AliESDVertex(0.,5.3,-1);
f5f6da22 329 points.Clear();
6fd990e3 330 return;
0c6af5c9 331 }
ecc64c3f 332
333 TH1F *hc = fZCombc;
ecc64c3f 334
ecc64c3f 335
8c42830a 336 if(hc->GetBinContent(hc->GetMaximumBin())<3)hc->Rebin(4);
debb3dde 337 Int_t binmin,binmax;
338 Int_t nPeaks=GetPeakRegion(hc,binmin,binmax);
339 if(nPeaks==2)AliWarning("2 peaks found");
7299b7a8 340 Float_t zm =0.;
341 Float_t ezm =0.;
342 Float_t lim1 = hc->GetBinLowEdge(binmin);
343 Float_t lim2 = hc->GetBinLowEdge(binmax)+hc->GetBinWidth(binmax);
344
345 if(nPeaks ==1 && (lim2-lim1)<fWindowWidth){
346 Float_t c=(lim1+lim2)/2.;
347 lim1=c-fWindowWidth/2.;
348 lim2=c+fWindowWidth/2.;
ecc64c3f 349 }
7299b7a8 350 Int_t niter = 0, ncontr=0;
351 do {
352 // symmetrization
353 if(zm !=0.){
354 Float_t semilarg=TMath::Min((lim2-zm),(zm-lim1));
355 lim1=zm - semilarg;
356 lim2=zm + semilarg;
0c6af5c9 357 }
7299b7a8 358
359 zm=0.;
360 ezm=0.;
361 ncontr=0;
f5f6da22 362 for(Int_t i =0; i<points.GetEntries(); i++){
363 AliITSZPoint* p=(AliITSZPoint*)points.UncheckedAt(i);
7299b7a8 364 if(p->GetZ()>lim1 && p->GetZ()<lim2){
365 Float_t deno = p->GetErrZ();
366 zm+=p->GetZ()/deno;
367 ezm+=1./deno;
368 ncontr++;
ecc64c3f 369 }
370 }
2b8b4286 371 if(ezm>0) {
372 zm/=ezm;
373 ezm=TMath::Sqrt(1./ezm);
374 }
7299b7a8 375 niter++;
376 } while(niter<10 && TMath::Abs((zm-lim1)-(lim2-zm))>fTolerance);
377 fCurrentVertex = new AliESDVertex(zm,ezm,ncontr);
0c6af5c9 378 fCurrentVertex->SetTitle("vertexer: B");
f5f6da22 379 points.Clear();
0c6af5c9 380 ResetHistograms();
6fd990e3 381 return;
0c6af5c9 382}
383
384//_____________________________________________________________________
385void AliITSVertexerZ::ResetHistograms(){
386 // delete TH1 data members
387 if(fZCombc)delete fZCombc;
0c6af5c9 388 fZCombc = 0;
0c6af5c9 389}
390
0c6af5c9 391//________________________________________________________
392void AliITSVertexerZ::PrintStatus() const {
393 // Print current status
394 cout <<"=======================================================\n";
395 cout <<" First layer first and last modules: "<<fFirstL1<<", ";
396 cout <<fLastL1<<endl;
397 cout <<" Second layer first and last modules: "<<fFirstL2<<", ";
398 cout <<fLastL2<<endl;
399 cout <<" Max Phi difference: "<<fDiffPhiMax<<endl;
400 cout <<"Limits for Z histograms: "<<fLowLim<<"; "<<fHighLim<<endl;
7299b7a8 401 cout <<"Bin sizes for coarse z histos "<<fStepCoarse<<endl;
0c6af5c9 402 cout <<" Current Z "<<fZFound<<"; Z sig "<<fZsig<<endl;
ecc64c3f 403 if(fZCombc){
404 cout<<"fZCombc exists - entries="<<fZCombc->GetEntries()<<endl;
405 }
406 else{
407 cout<<"fZCombc does not exist\n";
408 }
0c6af5c9 409
410 cout <<"=======================================================\n";
411}
412