1 /**************************************************************************
2 * Copyright(c) 1998-2003, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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 **************************************************************************/
15 #include "AliITSVertexerZ.h"
17 #include<TClonesArray.h>
21 #include "AliESDVertex.h"
22 #include "AliITSgeomTGeo.h"
23 #include "AliITSRecPoint.h"
24 #include "AliITSRecPointContainer.h"
25 #include "AliITSZPoint.h"
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 ////////////////////////////////////////////////////////////////
35 ClassImp(AliITSVertexerZ)
39 //______________________________________________________________________
40 AliITSVertexerZ::AliITSVertexerZ():AliITSVertexer(),
55 fSearchForPileup(kTRUE)
57 // Default constructor
59 SetFirstLayerModules();
60 SetSecondLayerModules();
70 //______________________________________________________________________
71 AliITSVertexerZ::AliITSVertexerZ(Float_t x0, Float_t y0):AliITSVertexer(),
86 fSearchForPileup(kTRUE)
88 // Standard Constructor
90 SetFirstLayerModules();
91 SetSecondLayerModules();
99 SetVtxStart((Double_t)x0,(Double_t)y0,0.);
103 //______________________________________________________________________
104 AliITSVertexerZ::~AliITSVertexerZ() {
109 //______________________________________________________________________
110 void AliITSVertexerZ::ConfigIterations(Int_t noiter,Float_t *ptr){
111 // configure the iterative procedure to gain efficiency for
112 // pp events with very low multiplicity
113 Float_t defaults[5]={0.02,0.05,0.1,0.2,0.3};
116 Error("ConfigIterations","Maximum number of iterations is 5\n");
119 for(Int_t j=0;j<5;j++)fPhiDiffIter[j]=defaults[j];
120 if(ptr)for(Int_t j=0;j<fMaxIter;j++)fPhiDiffIter[j]=ptr[j];
123 //______________________________________________________________________
124 Int_t AliITSVertexerZ::GetPeakRegion(TH1F*h, Int_t &binmin, Int_t &binmax){
125 // Finds a region around a peak in the Z histogram
126 // Case of 2 peaks is treated
127 Int_t imax=h->GetNbinsX();
129 Int_t bi1=h->GetMaximumBin();
131 for(Int_t i=imax;i>=1;i--){
132 if(h->GetBinContent(i)>maxval){
133 maxval=h->GetBinContent(i);
144 TH1F *copy = new TH1F(*h);
145 copy->SetBinContent(bi1,0.);
146 copy->SetBinContent(bi2,0.);
147 Int_t l1=TMath::Max(bi1-3,1);
148 Int_t l2=TMath::Min(bi1+3,h->GetNbinsX());
149 Float_t cont1=copy->Integral(l1,l2);
150 Int_t ll1=TMath::Max(bi2-3,1);
151 Int_t ll2=TMath::Min(bi2+3,h->GetNbinsX());
152 Float_t cont2=copy->Integral(ll1,ll2);
166 if(bi2-bi1==1) npeaks=1;
173 //______________________________________________________________________
174 AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(TTree *itsClusterTree){
175 // Defines the AliESDVertex for the current event
176 VertexZFinder(itsClusterTree);
178 for(Int_t iteraz=0;iteraz<fMaxIter;iteraz++){
179 if(fCurrentVertex) ntrackl=fCurrentVertex->GetNContributors();
180 if(!fCurrentVertex || ntrackl==0 || ntrackl==-1){
181 Float_t diffPhiMaxOrig=fDiffPhiMax;
182 fDiffPhiMax=GetPhiMaxIter(iteraz);
183 VertexZFinder(itsClusterTree);
184 fDiffPhiMax=diffPhiMaxOrig;
187 if(fComputeMultiplicity) FindMultiplicity(itsClusterTree);
188 return fCurrentVertex;
191 //______________________________________________________________________
192 void AliITSVertexerZ::VertexZFinder(TTree *itsClusterTree){
193 // Defines the AliESDVertex for the current event
195 Double_t startPos[3]={GetNominalPos()[0],GetNominalPos()[1],GetNominalPos()[2]};
196 Double_t startCov[6]={GetNominalCov()[0],GetNominalCov()[1],GetNominalCov()[2],
197 GetNominalCov()[3],GetNominalCov()[4],GetNominalCov()[5]};
199 TClonesArray *itsRec = 0;
200 // lc1 and gc1 are local and global coordinates for layer 1
201 Float_t gc1[3]={0.,0.,0.}; // ; for(Int_t ii=0; ii<3; ii++) gc1[ii]=0.;
202 // lc2 and gc2 are local and global coordinates for layer 2
203 Float_t gc2[3]={0.,0.,0.}; //; for(Int_t ii=0; ii<3; ii++) gc2[ii]=0.;
204 AliITSRecPointContainer* rpcont=AliITSRecPointContainer::Instance();
205 rpcont->FetchClusters(0,itsClusterTree);
206 if(!rpcont->IsSPDActive()){
207 AliWarning("Null pointer for RecPoints branch, vertex not calculated");
209 fCurrentVertex = new AliESDVertex(startPos,startCov,99999.,-2);
215 nrpL1=rpcont->GetNClustersInLayerFast(1);
216 nrpL2=rpcont->GetNClustersInLayerFast(2);
218 if(nrpL1 == 0 || nrpL2 == 0){
219 AliDebug(1,Form("No RecPoints in at least one SPD layer (%d %d)",nrpL1,nrpL2));
221 fCurrentVertex = new AliESDVertex(startPos,startCov,99999.,-2);
224 // Force a coarse bin size of 200 microns if the number of clusters on layer 2
226 if(nrpL2<fPPsetting[0])SetBinWidthCoarse(fPPsetting[1]);
227 // By default nbincoarse=(10+10)/0.01=2000
228 Int_t nbincoarse = static_cast<Int_t>((fHighLim-fLowLim)/fStepCoarse);
229 if(fZCombc)delete fZCombc;
230 fZCombc = new TH1F("fZCombc","Z",nbincoarse,fLowLim,fLowLim+nbincoarse*fStepCoarse);
232 /* Test the ffect of mutiple scatternig on error. Negligible
233 // Multiple scattering
234 Float_t beta=1.,pmed=0.875; //pmed=875 MeV (for tracks with dphi<0.01 rad)
235 Float_t beta2=beta*beta;
236 Float_t p2=pmed*pmed;
237 Float_t rBP=3; //Beam Pipe radius = 3cm
238 Float_t dBP=0.08/35.3; // 800 um of Be
239 Float_t dL1=0.01; //approx. 1% of radiation length
240 Float_t theta2BP=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dBP);
241 Float_t theta2L1=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dL1);
243 Int_t nEntriesMod[kNSPDMod];
244 TClonesArray* recpArr[kNSPDMod];
245 for(Int_t modul=0; modul<kNSPDMod; ++modul) {
246 if(!fUseModule[modul]) {
247 nEntriesMod[modul]=0;
250 recpArr[modul]=rpcont->UncheckedGetClusters(modul);
251 nEntriesMod[modul]=recpArr[modul]->GetEntriesFast();
255 Int_t maxdim=TMath::Min(nrpL1*nrpL2,50000); // temporary; to limit the size in PbPb
256 static TClonesArray points("AliITSZPoint",maxdim);
258 for(Int_t modul1= fFirstL1; modul1<=fLastL1;modul1++){ // Loop on modules of layer 1
259 if(!fUseModule[modul1]) continue;
260 UShort_t ladder=int(modul1/4)+1; // ladders are numbered starting from 1
261 TClonesArray *prpl1=recpArr[modul1]; //rpcont->UncheckedGetClusters(modul1);
262 Int_t nrecp1 = nEntriesMod[modul1]; //prpl1->GetEntries();
263 for(Int_t j1=0;j1<nrecp1;j1++){
264 AliITSRecPoint *recp1 = (AliITSRecPoint*)prpl1->At(j1);
265 recp1->GetGlobalXYZ(gc1);
266 gc1[0]-=GetNominalPos()[0]; // Possible beam offset in the bending plane
267 gc1[1]-=GetNominalPos()[1]; // " "
268 Float_t phi1 = TMath::ATan2(gc1[1],gc1[0]);
269 if(phi1<0)phi1+=TMath::TwoPi();
270 for(Int_t ladl2=0 ; ladl2<fLadOnLay2*2+1;ladl2++){
271 for(Int_t k=0;k<4;k++){
272 Int_t ladmod=fLadders[ladder-1]+ladl2;
273 if(ladmod>AliITSgeomTGeo::GetNLadders(2)) ladmod=ladmod-AliITSgeomTGeo::GetNLadders(2);
274 Int_t modul2=AliITSgeomTGeo::GetModuleIndex(2,ladmod,k+1);
275 if(modul2<0)continue;
276 if(!fUseModule[modul2]) continue;
277 itsRec=recpArr[modul2]; // rpcont->UncheckedGetClusters(modul2);
278 Int_t nrecp2 = nEntriesMod[modul2]; // itsRec->GetEntries();
279 for(Int_t j2=0;j2<nrecp2;j2++){
280 AliITSRecPoint *recp2 = (AliITSRecPoint*)itsRec->At(j2);
281 recp2->GetGlobalXYZ(gc2);
282 gc2[0]-=GetNominalPos()[0];
283 gc2[1]-=GetNominalPos()[1];
284 Float_t phi2 = TMath::ATan2(gc2[1],gc2[0]);
285 if(phi2<0)phi2+=TMath::TwoPi();
287 Float_t diff = TMath::Abs(phi2-phi1);
288 if(diff>TMath::Pi())diff=TMath::TwoPi()-diff;
289 if(diff<fDiffPhiMax){
290 Float_t r1=TMath::Sqrt(gc1[0]*gc1[0]+gc1[1]*gc1[1]);
292 Float_t erz1=recp1->GetSigmaZ2();
293 Float_t r2=TMath::Sqrt(gc2[0]*gc2[0]+gc2[1]*gc2[1]);
295 Float_t erz2=recp2->GetSigmaZ2();
296 // Float_t tgth=(zc2[j]-zc1[i])/(r2-r1); // slope (used for multiple scattering)
297 Float_t zr0=(r2*zc1-r1*zc2)/(r2-r1); //Z @ null radius
298 Float_t ezr0q=(r2*r2*erz1+r1*r1*erz2)/((r2-r1)*(r2-r1)); //error on Z @ null radius
300 // Multiple scattering
301 ezr0q+=r1*r1*(1+tgth*tgth)*theta2L1/2; // multiple scattering in layer 1
302 ezr0q+=rBP*rBP*(1+tgth*tgth)*theta2BP/2; // multiple scattering in beam pipe
304 if(nopoints<maxdim) new(points[nopoints++])AliITSZPoint(zr0,ezr0q);
315 Double_t contents = fZCombc->GetEntries()- fZCombc->GetBinContent(0)-fZCombc->GetBinContent(nbincoarse+1);
317 // Warning("FindVertexForCurrentEvent","Insufficient number of rec. points\n");
319 fCurrentVertex = new AliESDVertex(startPos,startCov,99999.,-1);
327 if(hc->GetBinContent(hc->GetMaximumBin())<3)hc->Rebin(4);
329 Int_t nPeaks=GetPeakRegion(hc,binmin,binmax);
330 if(nPeaks==2)AliDebug(2,"2 peaks found");
333 Float_t lim1 = hc->GetBinLowEdge(binmin);
334 Float_t lim2 = hc->GetBinLowEdge(binmax)+hc->GetBinWidth(binmax);
335 Float_t widthSR=lim2-lim1;
337 if(nPeaks ==1 && (lim2-lim1)<fWindowWidth){
338 Float_t c=(lim1+lim2)/2.;
339 lim1=c-fWindowWidth/2.;
340 lim2=c+fWindowWidth/2.;
342 Int_t niter = 0, ncontr=0;
346 Float_t semilarg=TMath::Min((lim2-zm),(zm-lim1));
354 for(Int_t i =0; i<points.GetEntriesFast(); i++){
355 AliITSZPoint* p=(AliITSZPoint*)points.UncheckedAt(i);
356 if(p->GetZ()>lim1 && p->GetZ()<lim2){
357 Float_t deno = p->GetErrZ();
365 ezm=TMath::Sqrt(1./ezm);
368 } while(niter<10 && TMath::Abs((zm-lim1)-(lim2-zm))>fTolerance);
369 if(nPeaks==2) ezm=widthSR;
370 Double_t position[3]={GetNominalPos()[0],GetNominalPos()[1],zm};
371 Double_t covmatrix[6]={GetNominalCov()[0],0.,GetNominalCov()[2],0.,0.,ezm};
372 fCurrentVertex = new AliESDVertex(position,covmatrix,99999.,ncontr);
373 fCurrentVertex->SetTitle("vertexer: Z");
374 fCurrentVertex->SetDispersion(fDiffPhiMax);
377 if(fSearchForPileup && ncontr>fMinTrackletsForPilup){
379 Int_t ncontr2=FindSecondPeak(fZCombc,binmin,binmax,secPeakPos);
380 if(ncontr2>=fMinTrackletsForPilup){
385 AliESDVertex secondVert(secPeakPos,0.1,ncontr2);
386 fVertArray = new AliESDVertex[2];
387 fVertArray[0]=(*fCurrentVertex);
388 fVertArray[1]=secondVert;
392 fVertArray = new AliESDVertex[1];
393 fVertArray[0]=(*fCurrentVertex);
400 //_____________________________________________________________________
401 Int_t AliITSVertexerZ::FindSecondPeak(TH1F* h, Int_t binmin,Int_t binmax, Float_t& secPeakPos){
402 // Resets bin contents between binmin and binmax and then search
403 // for a second peak position
404 for(Int_t i=binmin-1;i<=binmax+1;i++){
405 h->SetBinContent(i,0.);
407 Int_t secPeakBin=h->GetMaximumBin();
408 secPeakPos=h->GetBinCenter(secPeakBin);
409 Int_t secPeakCont=(Int_t)h->GetBinContent(secPeakBin);
410 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin-1);
411 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin+1);
412 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin-2);
413 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin+2);
417 //_____________________________________________________________________
418 void AliITSVertexerZ::ResetHistograms(){
419 // delete TH1 data members
420 if(fZCombc)delete fZCombc;
424 //________________________________________________________
425 void AliITSVertexerZ::PrintStatus() const {
426 // Print current status
427 cout <<"=======================================================\n";
428 cout <<" First layer first and last modules: "<<fFirstL1<<", ";
429 cout <<fLastL1<<endl;
430 cout <<" Second layer first and last modules: "<<fFirstL2<<", ";
431 cout <<fLastL2<<endl;
432 cout <<" Max Phi difference: "<<fDiffPhiMax<<endl;
433 cout <<"Limits for Z histograms: "<<fLowLim<<"; "<<fHighLim<<endl;
434 cout <<"Bin sizes for coarse z histos "<<fStepCoarse<<endl;
435 cout <<" Current Z "<<fZFound<<"; Z sig "<<fZsig<<endl;
437 cout<<"fZCombc exists - entries="<<fZCombc->GetEntries()<<endl;
440 cout<<"fZCombc does not exist\n";
443 cout <<"=======================================================\n";