X-Git-Url: http://git.uio.no/git/?a=blobdiff_plain;f=ITS%2FAliITSVertexerZ.cxx;h=d97b164113a79eef6fbec70f7ae3c844e2fae132;hb=8b40a6b84b6d4ab20a20287bf6d755ac01e27392;hp=9fdcd36145a6454ede5599c43275d2c016187dc5;hpb=ecc64c3f29d0ba10f97cb96ee82bd71df6ecfe60;p=u%2Fmrichter%2FAliRoot.git

diff --git a/ITS/AliITSVertexerZ.cxx b/ITS/AliITSVertexerZ.cxx
index 9fdcd36145a..d97b164113a 100644
--- a/ITS/AliITSVertexerZ.cxx
+++ b/ITS/AliITSVertexerZ.cxx
@@ -12,16 +12,20 @@
  * about the suitability of this software for any purpose. It is          *
  * provided "as is" without express or implied warranty.                  *
  **************************************************************************/
-#include <AliITSVertexerZ.h>
-#include <TString.h>
-#include "AliITSLoader.h"
+#include "AliITSVertexerZ.h"
 #include<TBranch.h>
 #include<TClonesArray.h>
+#include<TFile.h>
 #include<TH1.h>
+#include <TString.h>
 #include<TTree.h>
-#include <AliITSgeom.h>
+#include "AliITSLoader.h"
+#include "AliITSgeom.h"
 #include "AliITSDetTypeRec.h"
-#include <AliITSRecPoint.h>
+#include "AliITSRecPoint.h"
+#include "AliITSZPoint.h"
+#include "AliHeader.h"
+#include "AliGenEventHeader.h"
 
 /////////////////////////////////////////////////////////////////
 // this class implements a fast method to determine
@@ -36,60 +40,96 @@ ClassImp(AliITSVertexerZ)
 
 
 //______________________________________________________________________
-AliITSVertexerZ::AliITSVertexerZ():AliITSVertexer() {
+AliITSVertexerZ::AliITSVertexerZ():AliITSVertexer(),
+fFirstL1(0),
+fLastL1(0),
+fFirstL2(0),
+fLastL2(0),
+fDiffPhiMax(0),
+fX0(0.),
+fY0(0.),
+fZFound(0),
+fZsig(0.),
+fZCombc(0),
+fLowLim(0.),
+fHighLim(0.),
+fStepCoarse(0),
+fTolerance(0.),
+fMaxIter(0),
+fWindowWidth(0) {
   // Default constructor
-  SetDiffPhiMax(0);
-  fX0 = 0.;
-  fY0 = 0.;
-  SetFirstLayerModules(0);
-  SetSecondLayerModules(0);
-  fZFound = 0;
-  fZsig = 0.;
-  fZCombc = 0;
-  fZCombf = 0;
-  fZCombv = 0;
-  SetLowLimit(0.);
-  SetHighLimit(0.);
-  SetBinWidthCoarse(0.);
-  SetBinWidthFine(0.);
-  SetTolerance(0.);
-  SetPPsetting(0.,0.);
+  SetDiffPhiMax();
+  SetFirstLayerModules();
+  SetSecondLayerModules();
+  SetLowLimit();
+  SetHighLimit();
+  SetBinWidthCoarse();
+  SetTolerance();
+  SetPPsetting();
+  ConfigIterations();
+  SetWindowWidth();
 }
 
 //______________________________________________________________________
-AliITSVertexerZ::AliITSVertexerZ(TString fn, Float_t x0, Float_t y0):AliITSVertexer(fn) {
+AliITSVertexerZ::AliITSVertexerZ(TString fn, Float_t x0, Float_t y0):AliITSVertexer(fn),
+fFirstL1(0),
+fLastL1(0),
+fFirstL2(0),
+fLastL2(0),
+fDiffPhiMax(0),
+fX0(x0),
+fY0(y0),
+fZFound(0),
+fZsig(0.),
+fZCombc(0),
+fLowLim(0.),
+fHighLim(0.),
+fStepCoarse(0),
+fTolerance(0.),
+fMaxIter(0),
+fWindowWidth(0) {
   // Standard Constructor
   SetDiffPhiMax();
-  fX0 = x0;
-  fY0 = y0;
   SetFirstLayerModules();
   SetSecondLayerModules();
-  fZFound = 0;
-  fZsig = 0.;
-  fZCombc = 0;
-  fZCombf = 0;
-  fZCombv = 0;
   SetLowLimit();
   SetHighLimit();
   SetBinWidthCoarse();
-  SetBinWidthFine();
   SetTolerance();
   SetPPsetting();
+  ConfigIterations();
+  SetWindowWidth();
 
 }
 
 //______________________________________________________________________
-AliITSVertexerZ::AliITSVertexerZ(const AliITSVertexerZ &vtxr) : AliITSVertexer(vtxr) {
+AliITSVertexerZ::AliITSVertexerZ(const AliITSVertexerZ &vtxr) : AliITSVertexer(vtxr),
+fFirstL1(vtxr.fFirstL1),
+fLastL1(vtxr.fLastL1),
+fFirstL2(vtxr.fFirstL2),
+fLastL2(vtxr.fLastL2),
+fDiffPhiMax(vtxr.fDiffPhiMax),
+fX0(vtxr.fX0),
+fY0(vtxr.fY0),
+fZFound(vtxr.fZFound),
+fZsig(vtxr.fZsig),
+fZCombc(vtxr.fZCombc),
+fLowLim(vtxr.fLowLim),
+fHighLim(vtxr.fHighLim),
+fStepCoarse(vtxr.fStepCoarse),
+fTolerance(vtxr.fTolerance),
+fMaxIter(vtxr.fMaxIter),
+fWindowWidth(vtxr.fWindowWidth){
   // Copy constructor
-  // Copies are not allowed. The method is protected to avoid misuse.
-  Error("AliITSVertexerZ","Copy constructor not allowed\n");
+
 }
 
 //______________________________________________________________________
-AliITSVertexerZ& AliITSVertexerZ::operator=(const AliITSVertexerZ& /* vtxr */){
+AliITSVertexerZ& AliITSVertexerZ::operator=(const AliITSVertexerZ&  vtxr ){
   // Assignment operator
-  // Assignment is not allowed. The method is protected to avoid misuse.
-  Error("= operator","Assignment operator not allowed\n");
+
+  this->~AliITSVertexerZ();
+  new(this) AliITSVertexerZ(vtxr);
   return *this;
 }
 
@@ -97,22 +137,100 @@ AliITSVertexerZ& AliITSVertexerZ::operator=(const AliITSVertexerZ& /* vtxr */){
 AliITSVertexerZ::~AliITSVertexerZ() {
   // Destructor
   delete fZCombc;
-  delete fZCombf;
-  delete fZCombv;
 }
 
+//______________________________________________________________________
+void AliITSVertexerZ::ConfigIterations(Int_t noiter,Float_t *ptr){
+  // configure the iterative procedure to gain efficiency for
+  // pp events with very low multiplicity
+  Float_t defaults[5]={0.05,0.1,0.2,0.3,0.5};
+  fMaxIter=noiter;
+  if(noiter>5){
+    Error("ConfigIterations","Maximum number of iterations is 5\n");
+    fMaxIter=5;
+  }
+  for(Int_t j=0;j<5;j++)fPhiDiffIter[j]=defaults[j];
+  if(ptr)for(Int_t j=0;j<fMaxIter;j++)fPhiDiffIter[j]=ptr[j];
+}
+
+//______________________________________________________________________
+Int_t AliITSVertexerZ::GetPeakRegion(TH1F*h, Int_t &binmin, Int_t &binmax) const {
+  // Finds a region around a peak in the Z histogram
+  // Case of 2 peaks is treated 
+  Int_t imax=h->GetNbinsX();
+  Float_t maxval=0;
+  Int_t bi1=h->GetMaximumBin();
+  Int_t bi2=0;
+  for(Int_t i=imax;i>=1;i--){
+    if(h->GetBinContent(i)>maxval){
+      maxval=h->GetBinContent(i);
+      bi2=i;
+    }
+  }
+  Int_t npeaks=0;
+
+  if(bi1==bi2){
+    binmin=bi1-3;
+    binmax=bi1+3;
+    npeaks=1;
+  }else{
+    TH1F *copy = new TH1F(*h);
+    copy->SetBinContent(bi1,0.);
+    copy->SetBinContent(bi2,0.);
+    Int_t l1=TMath::Max(bi1-3,1);
+    Int_t l2=TMath::Min(bi1+3,h->GetNbinsX());
+    Float_t cont1=copy->Integral(l1,l2);
+    Int_t ll1=TMath::Max(bi2-3,1);
+    Int_t ll2=TMath::Min(bi2+3,h->GetNbinsX());
+    Float_t cont2=copy->Integral(ll1,ll2);
+    if(cont1>cont2){
+      binmin=l1;
+      binmax=l2;
+      npeaks=1;
+    }
+    if(cont2>cont1){
+      binmin=ll1;
+      binmax=ll2;
+      npeaks=1;
+    }
+    if(cont1==cont2){
+      binmin=l1;
+      binmax=ll2;
+      if(bi2-bi1==1) npeaks=1;
+      else npeaks=2;
+    }  
+    delete copy;
+  }    
+  return npeaks;
+}
 //______________________________________________________________________
 AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
   // Defines the AliESDVertex for the current event
-  
+  VertexZFinder(evnumber);
+  Int_t ntrackl=0;
+  for(Int_t iteraz=0;iteraz<fMaxIter;iteraz++){
+    if(fCurrentVertex) ntrackl=fCurrentVertex->GetNContributors();
+    if(!fCurrentVertex || ntrackl==0 || ntrackl==-1){
+      Float_t diffPhiMaxOrig=fDiffPhiMax;
+      fDiffPhiMax=GetPhiMaxIter(iteraz);
+      VertexZFinder(evnumber);
+      fDiffPhiMax=diffPhiMaxOrig;
+    }
+  }
+  FindMultiplicity(evnumber);
+  return fCurrentVertex;
+}  
+
+
+
+
+//______________________________________________________________________
+void AliITSVertexerZ::VertexZFinder(Int_t evnumber){
+  // Defines the AliESDVertex for the current event
   fCurrentVertex = 0;
   AliRunLoader *rl =AliRunLoader::GetRunLoader();
   AliITSLoader* itsLoader = (AliITSLoader*)rl->GetLoader("ITSLoader");
-  TDirectory * olddir = gDirectory;
-  rl->CdGAFile();
-  AliITSgeom* geom = (AliITSgeom*)gDirectory->Get("AliITSgeom");
-  olddir->cd();
-
+  AliITSgeom* geom = itsLoader->GetITSgeom();
   itsLoader->LoadRecPoints();
   rl->GetEvent(evnumber);
 
@@ -138,7 +256,7 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
   // This loop counts the number of recpoints on layer1 (central modules)
   for(Int_t module= fFirstL1; module<=fLastL1;module++){
     // Keep only central modules
-    if(module%4==0 || module%4==3)continue;
+    //    if(module%4==0 || module%4==3)continue;
     //   cout<<"Procesing module "<<module<<" ";
     branch->GetEvent(module);
     //    cout<<"Number of clusters "<<clusters->GetEntries()<<endl;
@@ -154,7 +272,9 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
   }
   if(nrpL1 == 0 || nrpL2 == 0){
     ResetHistograms();
-    return fCurrentVertex;
+    itsLoader->UnloadRecPoints();
+    fCurrentVertex = new AliESDVertex(0.,5.3,-2);
+    return;
   }
   // The vertex finding is attempted only if the number of RP is !=0 on
   // both layers
@@ -162,29 +282,25 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
   Float_t *yc1 = new Float_t [nrpL1];
   Float_t *zc1 = new Float_t [nrpL1];
   Float_t *phi1 = new Float_t [nrpL1];
+  Float_t *err1 = new Float_t [nrpL1];
   Float_t *xc2 = new Float_t [nrpL2]; // coordinates of the L1 Recpoints
   Float_t *yc2 = new Float_t [nrpL2];
   Float_t *zc2 = new Float_t [nrpL2];
   Float_t *phi2 = new Float_t [nrpL2];
+  Float_t *err2 = new Float_t [nrpL2];
   Int_t ind = 0;// running index for RP
   // Force a coarse bin size of 200 microns if the number of clusters on layer 2
   // is low
   if(nrpL2<fPPsetting[0])SetBinWidthCoarse(fPPsetting[1]);
-  // By default nbinfine = (10+10)/0.0005=40000
-  Int_t nbinfine = static_cast<Int_t>((fHighLim-fLowLim)/fStepFine);
   // By default nbincoarse=(10+10)/0.01=2000
   Int_t nbincoarse = static_cast<Int_t>((fHighLim-fLowLim)/fStepCoarse);
-  // Set stepverycoarse = 3*fStepCoarse
-  Int_t nbinvcoarse = static_cast<Int_t>((fHighLim-fLowLim)/(3.*fStepCoarse));
   if(fZCombc)delete fZCombc;
   fZCombc = new TH1F("fZCombc","Z",nbincoarse,fLowLim,fLowLim+nbincoarse*fStepCoarse);
-  if(fZCombv)delete fZCombv;
-  fZCombv = new TH1F("fZCombv","Z",nbinvcoarse,fLowLim,fLowLim+nbinvcoarse*3.*fStepCoarse);
-  if(fZCombf)delete fZCombf;
-  fZCombf = new TH1F("fZCombf","Z",nbinfine,fLowLim,fLowLim+nbinfine*fStepFine);
-  // Loop on modules of layer 1 (restricted to central modules)
+
+  // Loop on modules of layer 1 
+
   for(Int_t module= fFirstL1; module<=fLastL1;module++){
-    if(module%4==0 || module%4==3)continue;
+    //    if(module%4==0 || module%4==3)continue;
     branch->GetEvent(module);
     Int_t nrecp1 = itsRec->GetEntries();
     for(Int_t j=0;j<nrecp1;j++){
@@ -202,6 +318,7 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
       // azimuthal angle is computed in the interval 0 --> 2*pi
       phi1[ind] = TMath::ATan2(gc[1],gc[0]);
       if(phi1[ind]<0)phi1[ind]=2*TMath::Pi()+phi1[ind];
+      err1[ind]=recp->GetSigmaZ2();
       ind++;
     }
     detTypeRec.ResetRecPoints();
@@ -222,10 +339,26 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
       zc2[ind]=gc[2];
       phi2[ind] = TMath::ATan2(gc[1],gc[0]);
       if(phi2[ind]<0)phi2[ind]=2*TMath::Pi()+phi2[ind];
+      err2[ind]=recp->GetSigmaZ2();
       ind++;
     }
     detTypeRec.ResetRecPoints();
   }
+ 
+/* Test the ffect of mutiple scatternig on error. Negligible
+  // Multiple scattering
+  Float_t beta=1.,pmed=0.875; //pmed=875 MeV (for tracks with dphi<0.01 rad)
+  Float_t beta2=beta*beta;
+  Float_t p2=pmed*pmed;
+  Float_t rBP=3; //Beam Pipe radius = 3cm
+  Float_t dBP=0.08/35.3; // 800 um of Be
+  Float_t dL1=0.01; //approx. 1% of radiation length  
+  Float_t theta2BP=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dBP);
+  Float_t theta2L1=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(dL1);
+*/
+  TClonesArray *points = new TClonesArray("AliITSZPoint",nrpL1*nrpL2);
+  TClonesArray &pts = *points;
+  Int_t nopoints =0;
   for(Int_t i=0;i<nrpL1;i++){ // loop on L1 RP
     Float_t r1=TMath::Sqrt(xc1[i]*xc1[i]+yc1[i]*yc1[i]); // radius L1 RP
     for(Int_t j=0;j<nrpL2;j++){ // loop on L2 RP
@@ -233,10 +366,16 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
       if(diff>TMath::Pi())diff=2.*TMath::Pi()-diff; //diff<pi
       if(diff<fDiffPhiMax){ // cut on 10 milliradians by def.
 	Float_t r2=TMath::Sqrt(xc2[j]*xc2[j]+yc2[j]*yc2[j]); // radius L2 RP
+//	Float_t tgth=(zc2[j]-zc1[i])/(r2-r1); // slope
 	Float_t zr0=(r2*zc1[i]-r1*zc2[j])/(r2-r1); //Z @ null radius
-	fZCombf->Fill(zr0);
+	Float_t ezr0q=(r2*r2*err1[i]+r1*r1*err2[j])/(r2-r1)/(r2-r1); //error on Z @ null radius
+	/*
+        ezr0q+=r1*r1*(1+tgth*tgth)*theta2L1/2; // multiple scattering in layer 1
+        ezr0q+=rBP*rBP*(1+tgth*tgth)*theta2BP/2; // multiple scattering in beam pipe
+	*/
+	new(pts[nopoints++])AliITSZPoint(zr0,ezr0q);
+
 	fZCombc->Fill(zr0);
-	fZCombv->Fill(zr0);
       }
     }
   }
@@ -244,151 +383,78 @@ AliESDVertex* AliITSVertexerZ::FindVertexForCurrentEvent(Int_t evnumber){
   delete [] yc1;
   delete [] zc1;
   delete [] phi1;
+  delete [] err1;
   delete [] xc2;
   delete [] yc2;
   delete [] zc2;
   delete [] phi2;
-  if(fZCombc->GetEntries()==0){
-    Warning("FindVertexForCurrentEvent","Insufficient number of rec. points\n");
+  delete [] err2;
+
+  points->Sort();
+
+  Double_t contents = fZCombc->GetEntries()- fZCombc->GetBinContent(0)-fZCombc->GetBinContent(nbincoarse+1);
+  if(contents<1.){
+    //    Warning("FindVertexForCurrentEvent","Insufficient number of rec. points\n");
     ResetHistograms();
-    return fCurrentVertex;
-  }
-  /*
-  else {
-    if(fDebug>0)cout<<"Number of entries in hist. "<<fZCombc->GetEntries()<<endl;
+    itsLoader->UnloadRecPoints();
+    fCurrentVertex = new AliESDVertex(0.,5.3,-1);
+    return;
   }
-  */
 
   TH1F *hc = fZCombc;
-  Bool_t goon = kFALSE;
-  Int_t cnt = 0;
-  Int_t bi;
-
-  do {
-    goon = kFALSE;
-    cnt++;
-    bi = hc->GetMaximumBin();   // bin with maximal content on coarse histogram
-    if(hc->GetBinContent(bi)<3){
-      if(cnt==1)goon = kTRUE;
-      hc = fZCombv;
-    }
-  } while(goon);
 
-
-  Float_t centre = hc->GetBinCenter(bi);  // z value of the bin with maximal content
   
-  // evaluation of the centroid
-  Int_t ii1=TMath::Max(bi-3,1);
-  Int_t ii2=TMath::Min(bi+3,hc->GetNbinsX());
-  centre = 0.;
-  Int_t nn=0;
-  for(Int_t ii=ii1;ii<ii2;ii++){
-    centre+= hc->GetBinCenter(ii)*hc->GetBinContent(ii);
-    nn+=static_cast<Int_t>(hc->GetBinContent(ii));
-  }
-  centre/=nn;
-  /*
-  if(fDebug>0){
-    cout<<"Value of center "<<centre<<endl;
-    cout<<"Population of 3 central bins: "<<hc->GetBinContent(bi-1)<<", ";
-    cout<<hc->GetBinContent(bi)<<", ";
-    cout<<hc->GetBinContent(bi+1)<<endl;
+  if(hc->GetBinContent(hc->GetMaximumBin())<3)hc->Rebin(3);
+  Int_t binmin,binmax;
+  Int_t nPeaks=GetPeakRegion(hc,binmin,binmax);   
+  if(nPeaks==2)AliWarning("2 peaks found");
+  Float_t zm =0.;
+  Float_t ezm =0.;
+  Float_t lim1 = hc->GetBinLowEdge(binmin);
+  Float_t lim2 = hc->GetBinLowEdge(binmax)+hc->GetBinWidth(binmax);
+
+  if(nPeaks ==1 && (lim2-lim1)<fWindowWidth){
+    Float_t c=(lim1+lim2)/2.;
+    lim1=c-fWindowWidth/2.;
+    lim2=c+fWindowWidth/2.;
   }
-  */
-  // n1 is the bin number of fine histogram containing the point located 1 coarse bin less than "centre"
-  Int_t n1 = static_cast<Int_t>((centre-hc->GetBinWidth(bi)-fZCombf->GetBinLowEdge(0))/fStepFine);
-  // n2 is the bin number of fine histogram containing the point located 1 coarse bin more than "centre"
-  Int_t n2 = static_cast<Int_t>((centre+hc->GetBinWidth(bi)-fZCombf->GetBinLowEdge(0))/fStepFine);
-  if(n1<1)n1=1;
-  if(n2>nbinfine)n2=nbinfine;
-  Int_t niter = 0;
-  goon = kTRUE;
-  Int_t num=0;
-  Bool_t last = kFALSE;
-
-  while(goon || last){
-    fZFound = 0.;
-    fZsig = 0.;
-    num=0;
-    // at the end of the loop:
-    // fZFound = N*(Average Z) - where N is the number of tracklets
-    // num=N
-    // fZsig = N*Q - where Q is the average of Z*Z
-    for(Int_t n=n1;n<=n2;n++){
-      fZFound+=fZCombf->GetBinCenter(n)*fZCombf->GetBinContent(n);
-      num+=static_cast<Int_t>(fZCombf->GetBinContent(n));
-      fZsig+=fZCombf->GetBinCenter(n)*fZCombf->GetBinCenter(n)*fZCombf->GetBinContent(n);
-    }
-    if(num<2){
-      fZsig = 0.;
-    }
-    else{
-      Float_t radi =  fZsig/(num-1)-fZFound*fZFound/num/(num-1);
-      // radi = square root of sample variance of Z
-      if(radi>0.)fZsig=TMath::Sqrt(radi);
-      else fZsig=0.;
-      // fZfound - Average Z
-      fZFound/=num;
+  Int_t niter = 0, ncontr=0;
+  do {
+    // symmetrization
+    if(zm  !=0.){
+      Float_t semilarg=TMath::Min((lim2-zm),(zm-lim1));
+      lim1=zm - semilarg;
+      lim2=zm + semilarg;
     }
-    if(!last){
-      // goon is true if the distance between the found Z and the lower bin differs from the distance between the found Z and
-      // the upper bin by more than tolerance (0.002)
-      goon = TMath::Abs(TMath::Abs(fZFound-fZCombf->GetBinCenter(n1))-TMath::Abs(fZFound-fZCombf->GetBinCenter(n2)))>fTolerance;
-      // a window in the fine grained histogram is centered aroung the found Z. The width is 2 bins of
-      // the coarse grained histogram
-      n1 = static_cast<Int_t>((fZFound-hc->GetBinWidth(bi)-fZCombf->GetBinLowEdge(0))/fStepFine);
-      if(n1<1)n1=1;
-      n2 = static_cast<Int_t>((fZFound+hc->GetBinWidth(bi)-fZCombf->GetBinLowEdge(0))/fStepFine);
-      if(n2>nbinfine)n2=nbinfine;
-      /*
-      if(fDebug>0){
-	cout<<"Search restricted to n1 = "<<n1<<", n2= "<<n2<<endl;
-	cout<<"z1= "<<fZCombf->GetBinCenter(n1)<<", n2 = "<<fZCombf->GetBinCenter(n2)<<endl;
-      }
-      */
-      niter++;
-      // no more than 10 adjusting iterations
-      if(niter>=10){
-	goon = kFALSE;
-	Warning("FindVertexForCurrentEvent","The procedure dows not converge\n");
-      }
 
-      if((fZsig> 0.0001) && !goon && num>5){
-	last = kTRUE;
-	n1 = static_cast<Int_t>((fZFound-fZsig-fZCombf->GetBinLowEdge(0))/fZCombf->GetBinWidth(0));
-	if(n1<1)n1=1;
-	n2 = static_cast<Int_t>((fZFound+fZsig-fZCombf->GetBinLowEdge(0))/fZCombf->GetBinWidth(0));
-	if(n2>nbinfine)n2=nbinfine;
-	/*
-	if(fDebug>0){
-	  cout<<"FINAL Search restricted to n1 = "<<n1<<", n2= "<<n2<<endl;
-	  cout<<"z1= "<<fZCombf->GetBinCenter(n1)<<", n2 = "<<fZCombf->GetBinCenter(n2)<<endl;
-	}
-	*/
+    zm=0.;
+    ezm=0.;
+    ncontr=0;
+    for(Int_t i =0; i<points->GetEntriesFast(); i++){
+      AliITSZPoint* p=(AliITSZPoint*)points->UncheckedAt(i);
+      if(p->GetZ()>lim1 && p->GetZ()<lim2){
+        Float_t deno = p->GetErrZ();
+        zm+=p->GetZ()/deno;
+        ezm+=1./deno;
+        ncontr++;
       }
     }
-    else {
-      last = kFALSE;
-    }
-
-  }
-  //  if(fDebug>0)cout<<"Numer of Iterations "<<niter<<endl<<endl;
-  if(num!=0)fZsig/=TMath::Sqrt(num);
-  fCurrentVertex = new AliESDVertex(fZFound,fZsig,num);
+    zm/=ezm;
+    ezm=TMath::Sqrt(1./ezm);
+    niter++;
+  } while(niter<10 && TMath::Abs((zm-lim1)-(lim2-zm))>fTolerance);
+  fCurrentVertex = new AliESDVertex(zm,ezm,ncontr);
   fCurrentVertex->SetTitle("vertexer: B");
   ResetHistograms();
-  return fCurrentVertex;
+  itsLoader->UnloadRecPoints();
+  return;
 }
 
 //_____________________________________________________________________
 void AliITSVertexerZ::ResetHistograms(){
   // delete TH1 data members
   if(fZCombc)delete fZCombc;
-  if(fZCombf)delete fZCombf;
-  if(fZCombv)delete fZCombv;
   fZCombc = 0;
-  fZCombf = 0;
-  fZCombv = 0;
 }
 
 //______________________________________________________________________
@@ -398,20 +464,12 @@ void AliITSVertexerZ::FindVertices(){
   AliITSLoader* itsLoader =  (AliITSLoader*) rl->GetLoader("ITSLoader");
   itsLoader->ReloadRecPoints();
   for(Int_t i=fFirstEvent;i<=fLastEvent;i++){
-    cout<<"Processing event "<<i<<endl;
+    //  cout<<"Processing event "<<i<<endl;
     rl->GetEvent(i);
     FindVertexForCurrentEvent(i);
     if(fCurrentVertex){
       WriteCurrentVertex();
     }
-    /*
-    else {
-      if(fDebug>0){
-	cout<<"Vertex not found for event "<<i<<endl;
-	cout<<"fZFound = "<<fZFound<<", fZsig= "<<fZsig<<endl;
-      }
-    }
-    */
   }
 }
 
@@ -425,7 +483,7 @@ void AliITSVertexerZ::PrintStatus() const {
   cout <<fLastL2<<endl;
   cout <<" Max Phi difference: "<<fDiffPhiMax<<endl;
   cout <<"Limits for Z histograms: "<<fLowLim<<"; "<<fHighLim<<endl;
-  cout <<"Bin sizes for coarse and fine z histos "<<fStepCoarse<<"; "<<fStepFine<<endl;
+  cout <<"Bin sizes for coarse z histos "<<fStepCoarse<<endl;
   cout <<" Current Z "<<fZFound<<"; Z sig "<<fZsig<<endl;
   cout <<" Debug flag: "<<fDebug<<endl;
   cout <<"First event to be processed "<<fFirstEvent;
@@ -436,18 +494,6 @@ void AliITSVertexerZ::PrintStatus() const {
   else{
     cout<<"fZCombc does not exist\n";
   }
-  if(fZCombv){
-    cout<<"fZCombv exists - entries="<<fZCombv->GetEntries()<<endl;
-  }
-  else{
-    cout<<"fZCombv does not exist\n";
-  }
-   if(fZCombf){
-    cout<<"fZCombf exists - entries="<<fZCombv->GetEntries()<<endl;
-  }
-  else{
-    cout<<"fZCombf does not exist\n";
-  }
  
   cout <<"=======================================================\n";
 }