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 // Default constructor
57 SetFirstLayerModules();
58 SetSecondLayerModules();
68 //______________________________________________________________________
69 AliITSVertexerZ::AliITSVertexerZ(Float_t x0, Float_t y0):AliITSVertexer(),
84 // Standard Constructor
86 SetFirstLayerModules();
87 SetSecondLayerModules();
95 SetVtxStart((Double_t)x0,(Double_t)y0,0.);
99 //______________________________________________________________________
100 AliITSVertexerZ::~AliITSVertexerZ() {
105 //______________________________________________________________________
106 void 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]={0.02,0.05,0.1,0.2,0.3};
112 Error("ConfigIterations","Maximum number of iterations is 5\n");
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];
119 //______________________________________________________________________
120 Int_t AliITSVertexerZ::GetPeakRegion(TH1F*h, Int_t &binmin, Int_t &binmax){
121 // Finds a region around a peak in the Z histogram
122 // Case of 2 peaks is treated
123 Int_t imax=h->GetNbinsX();
125 Int_t bi1=h->GetMaximumBin();
127 for(Int_t i=imax;i>=1;i--){
128 if(h->GetBinContent(i)>maxval){
129 maxval=h->GetBinContent(i);
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);
162 if(bi2-bi1==1) npeaks=1;
169 //______________________________________________________________________
170 AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(TTree *itsClusterTree){
171 // Defines the AliESDVertex for the current event
172 VertexZFinder(itsClusterTree);
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);
179 VertexZFinder(itsClusterTree);
180 fDiffPhiMax=diffPhiMaxOrig;
183 FindMultiplicity(itsClusterTree);
184 return fCurrentVertex;
187 //______________________________________________________________________
188 void AliITSVertexerZ::VertexZFinder(TTree *itsClusterTree){
189 // Defines the AliESDVertex for the current event
192 TClonesArray *itsRec = 0;
193 // lc1 and gc1 are local and global coordinates for layer 1
194 Float_t lc1[3]; for(Int_t ii=0; ii<3; ii++) lc1[ii]=0.;
195 Float_t gc1[3]; for(Int_t ii=0; ii<3; ii++) gc1[ii]=0.;
196 // lc2 and gc2 are local and global coordinates for layer 2
197 Float_t lc2[3]; for(Int_t ii=0; ii<3; ii++) lc2[ii]=0.;
198 Float_t gc2[3]; for(Int_t ii=0; ii<3; ii++) gc2[ii]=0.;
199 AliITSRecPointContainer* rpcont=AliITSRecPointContainer::Instance();
200 itsRec=rpcont->FetchClusters(0,itsClusterTree);
201 if(!rpcont->IsSPDActive()){
202 AliWarning("Null pointer for RecPoints branch, vertex not calculated");
204 fCurrentVertex = new AliESDVertex(0.,5.3,-2);
210 nrpL1=rpcont->GetNClustersInLayerFast(1);
211 nrpL2=rpcont->GetNClustersInLayerFast(2);
213 if(nrpL1 == 0 || nrpL2 == 0){
214 AliDebug(1,Form("No RecPoints in at least one SPD layer (%d %d)",nrpL1,nrpL2));
216 fCurrentVertex = new AliESDVertex(0.,5.3,-2);
219 // Force a coarse bin size of 200 microns if the number of clusters on layer 2
221 if(nrpL2<fPPsetting[0])SetBinWidthCoarse(fPPsetting[1]);
222 // By default nbincoarse=(10+10)/0.01=2000
223 Int_t nbincoarse = static_cast<Int_t>((fHighLim-fLowLim)/fStepCoarse);
224 if(fZCombc)delete fZCombc;
225 fZCombc = new TH1F("fZCombc","Z",nbincoarse,fLowLim,fLowLim+nbincoarse*fStepCoarse);
227 /* Test the ffect of mutiple scatternig on error. Negligible
228 // Multiple scattering
229 Float_t beta=1.,pmed=0.875; //pmed=875 MeV (for tracks with dphi<0.01 rad)
230 Float_t beta2=beta*beta;
231 Float_t p2=pmed*pmed;
232 Float_t rBP=3; //Beam Pipe radius = 3cm
233 Float_t dBP=0.08/35.3; // 800 um of Be
234 Float_t dL1=0.01; //approx. 1% of radiation length
235 Float_t theta2BP=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dBP);
236 Float_t theta2L1=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dL1);
238 Int_t maxdim=TMath::Min(nrpL1*nrpL2,50000); // temporary; to limit the size in PbPb
239 static TClonesArray points("AliITSZPoint",maxdim);
241 for(Int_t modul1= fFirstL1; modul1<=fLastL1;modul1++){ // Loop on modules of layer 1
242 if(!fUseModule[modul1]) continue;
243 UShort_t ladder=int(modul1/4)+1; // ladders are numbered starting from 1
244 TClonesArray *prpl1=rpcont->UncheckedGetClusters(modul1);
245 Int_t nrecp1 = prpl1->GetEntries();
246 for(Int_t j1=0;j1<nrecp1;j1++){
247 AliITSRecPoint *recp = (AliITSRecPoint*)prpl1->At(j1);
248 recp->GetGlobalXYZ(gc1);
249 gc1[0]-=GetNominalPos()[0]; // Possible beam offset in the bending plane
250 gc1[1]-=GetNominalPos()[1]; // " "
251 Float_t r1=TMath::Sqrt(gc1[0]*gc1[0]+gc1[1]*gc1[1]);
252 Float_t phi1 = TMath::ATan2(gc1[1],gc1[0]);
253 if(phi1<0)phi1+=2*TMath::Pi();
255 Float_t erz1=recp->GetSigmaZ2();
256 for(Int_t ladl2=0 ; ladl2<fLadOnLay2*2+1;ladl2++){
257 for(Int_t k=0;k<4;k++){
258 Int_t ladmod=fLadders[ladder-1]+ladl2;
259 if(ladmod>AliITSgeomTGeo::GetNLadders(2)) ladmod=ladmod-AliITSgeomTGeo::GetNLadders(2);
260 Int_t modul2=AliITSgeomTGeo::GetModuleIndex(2,ladmod,k+1);
261 if(!fUseModule[modul2]) continue;
262 itsRec=rpcont->UncheckedGetClusters(modul2);
263 Int_t nrecp2 = itsRec->GetEntries();
264 for(Int_t j2=0;j2<nrecp2;j2++){
265 recp = (AliITSRecPoint*)itsRec->At(j2);
266 recp->GetGlobalXYZ(gc2);
267 gc2[0]-=GetNominalPos()[0];
268 gc2[1]-=GetNominalPos()[1];
269 Float_t r2=TMath::Sqrt(gc2[0]*gc2[0]+gc2[1]*gc2[1]);
270 Float_t phi2 = TMath::ATan2(gc2[1],gc2[0]);
271 if(phi2<0)phi2+=2*TMath::Pi();
273 Float_t erz2=recp->GetSigmaZ2();
275 Float_t diff = TMath::Abs(phi2-phi1);
276 if(diff>TMath::Pi())diff=2.*TMath::Pi()-diff;
277 if(diff<fDiffPhiMax){
278 // Float_t tgth=(zc2[j]-zc1[i])/(r2-r1); // slope (used for multiple scattering)
279 Float_t zr0=(r2*zc1-r1*zc2)/(r2-r1); //Z @ null radius
280 Float_t ezr0q=(r2*r2*erz1+r1*r1*erz2)/(r2-r1)/(r2-r1); //error on Z @ null radius
282 // Multiple scattering
283 ezr0q+=r1*r1*(1+tgth*tgth)*theta2L1/2; // multiple scattering in layer 1
284 ezr0q+=rBP*rBP*(1+tgth*tgth)*theta2BP/2; // multiple scattering in beam pipe
286 if(nopoints<maxdim) new(points[nopoints++])AliITSZPoint(zr0,ezr0q);
297 Double_t contents = fZCombc->GetEntries()- fZCombc->GetBinContent(0)-fZCombc->GetBinContent(nbincoarse+1);
299 // Warning("FindVertexForCurrentEvent","Insufficient number of rec. points\n");
301 fCurrentVertex = new AliESDVertex(0.,5.3,-1);
309 if(hc->GetBinContent(hc->GetMaximumBin())<3)hc->Rebin(4);
311 Int_t nPeaks=GetPeakRegion(hc,binmin,binmax);
312 if(nPeaks==2)AliDebug(2,"2 peaks found");
315 Float_t lim1 = hc->GetBinLowEdge(binmin);
316 Float_t lim2 = hc->GetBinLowEdge(binmax)+hc->GetBinWidth(binmax);
317 Float_t widthSR=lim2-lim1;
319 if(nPeaks ==1 && (lim2-lim1)<fWindowWidth){
320 Float_t c=(lim1+lim2)/2.;
321 lim1=c-fWindowWidth/2.;
322 lim2=c+fWindowWidth/2.;
324 Int_t niter = 0, ncontr=0;
328 Float_t semilarg=TMath::Min((lim2-zm),(zm-lim1));
336 for(Int_t i =0; i<points.GetEntries(); i++){
337 AliITSZPoint* p=(AliITSZPoint*)points.UncheckedAt(i);
338 if(p->GetZ()>lim1 && p->GetZ()<lim2){
339 Float_t deno = p->GetErrZ();
347 ezm=TMath::Sqrt(1./ezm);
350 } while(niter<10 && TMath::Abs((zm-lim1)-(lim2-zm))>fTolerance);
351 if(nPeaks==2) ezm=widthSR;
352 fCurrentVertex = new AliESDVertex(zm,ezm,ncontr);
353 fCurrentVertex->SetTitle("vertexer: Z");
354 fCurrentVertex->SetDispersion(fDiffPhiMax);
357 if(ncontr>fMinTrackletsForPilup){
359 Int_t ncontr2=FindSecondPeak(fZCombc,binmin,binmax,secPeakPos);
360 if(ncontr2>=fMinTrackletsForPilup){
365 AliESDVertex secondVert(secPeakPos,0.1,ncontr2);
366 fVertArray = new AliESDVertex[2];
367 fVertArray[0]=(*fCurrentVertex);
368 fVertArray[1]=secondVert;
372 fVertArray = new AliESDVertex[1];
373 fVertArray[0]=(*fCurrentVertex);
380 //_____________________________________________________________________
381 Int_t AliITSVertexerZ::FindSecondPeak(TH1F* h, Int_t binmin,Int_t binmax, Float_t& secPeakPos){
382 for(Int_t i=binmin-1;i<=binmax+1;i++){
383 h->SetBinContent(i,0.);
385 Int_t secPeakBin=h->GetMaximumBin();
386 secPeakPos=h->GetBinCenter(secPeakBin);
387 Int_t secPeakCont=(Int_t)h->GetBinContent(secPeakBin);
388 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin-1);
389 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin+1);
390 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin-2);
391 secPeakCont+=(Int_t)h->GetBinContent(secPeakBin+2);
395 //_____________________________________________________________________
396 void AliITSVertexerZ::ResetHistograms(){
397 // delete TH1 data members
398 if(fZCombc)delete fZCombc;
402 //________________________________________________________
403 void AliITSVertexerZ::PrintStatus() const {
404 // Print current status
405 cout <<"=======================================================\n";
406 cout <<" First layer first and last modules: "<<fFirstL1<<", ";
407 cout <<fLastL1<<endl;
408 cout <<" Second layer first and last modules: "<<fFirstL2<<", ";
409 cout <<fLastL2<<endl;
410 cout <<" Max Phi difference: "<<fDiffPhiMax<<endl;
411 cout <<"Limits for Z histograms: "<<fLowLim<<"; "<<fHighLim<<endl;
412 cout <<"Bin sizes for coarse z histos "<<fStepCoarse<<endl;
413 cout <<" Current Z "<<fZFound<<"; Z sig "<<fZsig<<endl;
415 cout<<"fZCombc exists - entries="<<fZCombc->GetEntries()<<endl;
418 cout<<"fZCombc does not exist\n";
421 cout <<"=======================================================\n";