[u/mrichter/AliRoot.git] / ITS / AliV0vertexer.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

//-------------------------------------------------------------------------
//               Implementation of the V0 vertexer class
//
//     Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch
//-------------------------------------------------------------------------
#include <TFile.h>
#include <TTree.h>
#include <TObjArray.h>
#include "Riostream.h"

#include "AliV0vertex.h"
#include "AliV0vertexer.h"
#include "AliITStrackV2.h"

ClassImp(AliV0vertexer)

Int_t AliV0vertexer::Tracks2V0vertices(const TFile *inp, TFile *out) {
  //--------------------------------------------------------------------
  //This function reconstructs V0 vertices
  //--------------------------------------------------------------------
   TFile *in=(TFile*)inp;
   TDirectory *savedir=gDirectory; 

   if (!in->IsOpen()) {
     cerr<<"AliV0vertexer::Tracks2V0vertices(): ";
     cerr<<"file with ITS tracks has not been open !\n";
     return 1;
   }

   if (!out->IsOpen()) {
     cerr<<"AliV0vertexer::Tracks2V0vertices(): ";
     cerr<<"file for V0 vertices has not been open !\n";
     return 2;
   }

   in->cd();

   Char_t name[100];
   sprintf(name,"TreeT_ITS_%d",fEventN);
   TTree *trkTree=(TTree*)in->Get(name);
   TBranch *branch=trkTree->GetBranch("tracks");
   Int_t nentr=(Int_t)trkTree->GetEntries();

   TObjArray negtrks(nentr/2);
   TObjArray postrks(nentr/2);

   Int_t nneg=0, npos=0, nvtx=0;

   Int_t i;
   for (i=0; i<nentr; i++) {
       AliITStrackV2 *iotrack=new AliITStrackV2;
       branch->SetAddress(&iotrack);
       trkTree->GetEvent(i);

       iotrack->PropagateTo(3.,0.0023,65.19); iotrack->PropagateTo(2.5,0.,0.);

       if (iotrack->Get1Pt() > 0.) {nneg++; negtrks.AddLast(iotrack);}
       else {npos++; postrks.AddLast(iotrack);}
   }   


   out->cd();
   sprintf(name,"TreeV%d",fEventN);
   TTree vtxTree(name,"Tree with V0 vertices");
   AliV0vertex *ioVertex=0;
   vtxTree.Branch("vertices","AliV0vertex",&ioVertex,32000,0);


   for (i=0; i<nneg; i++) {
      if (i%10==0) cerr<<nneg-i<<'\r';
      AliITStrackV2 *ntrk=(AliITStrackV2 *)negtrks.UncheckedAt(i);

      if (TMath::Abs(ntrk->GetD(fX,fY))<fDPmin) continue;
      if (TMath::Abs(ntrk->GetD(fX,fY))>fRmax) continue;

      for (Int_t k=0; k<npos; k++) {
         AliITStrackV2 *ptrk=(AliITStrackV2 *)postrks.UncheckedAt(k);

         if (TMath::Abs(ptrk->GetD(fX,fY))<fDPmin) continue;
         if (TMath::Abs(ptrk->GetD(fX,fY))>fRmax) continue;

         if (TMath::Abs(ntrk->GetD(fX,fY))<fDNmin)
         if (TMath::Abs(ptrk->GetD(fX,fY))<fDNmin) continue;


         AliITStrackV2 nt(*ntrk), pt(*ptrk), *pnt=&nt, *ppt=&pt;

         Double_t dca=PropagateToDCA(pnt,ppt);
         if (dca > fDCAmax) continue;

         AliV0vertex vertex(*pnt,*ppt);
         if (vertex.GetChi2() > fChi2max) continue;
	 
         /*  Think of something better here ! 
         nt.PropagateToVertex(); if (TMath::Abs(nt.GetZ())<0.04) continue;
         pt.PropagateToVertex(); if (TMath::Abs(pt.GetZ())<0.04) continue;
	 */

         Double_t x,y,z; vertex.GetXYZ(x,y,z); 
         Double_t r2=x*x + y*y; 
         if (r2 > fRmax*fRmax) continue;
         if (r2 < fRmin*fRmin) continue;

         Double_t px,py,pz; vertex.GetPxPyPz(px,py,pz);
         Double_t p2=px*px+py*py+pz*pz;
         Double_t cost=((x-fX)*px + (y-fY)*py + (z-fZ)*pz)/
                TMath::Sqrt(p2*((x-fX)*(x-fX) + (y-fY)*(y-fY) + (z-fZ)*(z-fZ)));

         //if (cost < (5*fCPAmax-0.9-TMath::Sqrt(r2)*(fCPAmax-1))/4.1) continue;
         if (cost < fCPAmax) continue;

         //vertex.ChangeMassHypothesis(); //default is Lambda0 

         ioVertex=&vertex; vtxTree.Fill();

         nvtx++;
      }
   }

   cerr<<"Number of reconstructed V0 vertices: "<<nvtx<<endl;

   vtxTree.Write();

   negtrks.Delete();
   postrks.Delete();

   savedir->cd();
   
   delete trkTree;

   return 0;
}


static void External2Helix(const AliITStrackV2 *t, Double_t helix[6]) { 
  //--------------------------------------------------------------------
  // External track parameters -> helix parameters 
  //--------------------------------------------------------------------
  Double_t alpha,x,cs,sn;
  t->GetExternalParameters(x,helix); alpha=t->GetAlpha();

  cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
  helix[5]=x*cs - helix[0]*sn;            // x0
  helix[0]=x*sn + helix[0]*cs;            // y0
//helix[1]=                               // z0
  helix[2]=TMath::ASin(helix[2]) + alpha; // phi0
//helix[3]=                               // tgl
  helix[4]=helix[4]/t->GetConvConst();    // C
}

static void Evaluate(const Double_t *h, Double_t t,
                     Double_t r[3],  //radius vector
                     Double_t g[3],  //first defivatives
                     Double_t gg[3]) //second derivatives
{
  //--------------------------------------------------------------------
  // Calculate position of a point on a track and some derivatives
  //--------------------------------------------------------------------
  Double_t phase=h[4]*t+h[2];
  Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);

  r[0] = h[5] + (sn - h[6])/h[4];
  r[1] = h[0] - (cs - h[7])/h[4];  
  r[2] = h[1] + h[3]*t;

  g[0] = cs; g[1]=sn; g[2]=h[3];
  
  gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
}

Double_t AliV0vertexer::PropagateToDCA(AliITStrackV2 *n, AliITStrackV2 *p) {
  //--------------------------------------------------------------------
  // This function returns the DCA between two tracks
  // The tracks will be moved to the point of DCA ! 
  //--------------------------------------------------------------------
  Double_t dy2=n->GetSigmaY2() + p->GetSigmaY2();
  Double_t dz2=n->GetSigmaZ2() + p->GetSigmaZ2();
  Double_t dx2=dy2; 

  //dx2=dy2=dz2=1.;

  Double_t p1[8]; External2Helix(n,p1);
  p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
  Double_t p2[8]; External2Helix(p,p2);
  p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);


  Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
  Evaluate(p1,t1,r1,g1,gg1);
  Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
  Evaluate(p2,t2,r2,g2,gg2);

  Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
  Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;

  Int_t max=27;
  while (max--) {
     Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
     Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
     Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 + 
                  (g1[1]*g1[1] - dy*gg1[1])/dy2 +
                  (g1[2]*g1[2] - dz*gg1[2])/dz2;
     Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 + 
                  (g2[1]*g2[1] + dy*gg2[1])/dy2 +
                  (g2[2]*g2[2] + dz*gg2[2])/dz2;
     Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);

     Double_t det=h11*h22-h12*h12;

     Double_t dt1,dt2;
     if (TMath::Abs(det)<1.e-33) {
        //(quasi)singular Hessian
        dt1=-gt1; dt2=-gt2;
     } else {
        dt1=-(gt1*h22 - gt2*h12)/det; 
        dt2=-(h11*gt2 - h12*gt1)/det;
     }

     if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}

     //check delta(phase1) ?
     //check delta(phase2) ?

     if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
     if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
        if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2) 
	   cerr<<"AliV0vertexer::PropagateToDCA:"
                 " stopped at not a stationary point !\n";
        Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
        if (lmb < 0.) 
	   cerr<<"AliV0vertexer::PropagateToDCA:"
                 " stopped at not a minimum !\n";
        break;
     }

     Double_t dd=dm;
     for (Int_t div=1 ; ; div*=2) {
        Evaluate(p1,t1+dt1,r1,g1,gg1);
        Evaluate(p2,t2+dt2,r2,g2,gg2);
        dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
        dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
	if (dd<dm) break;
        dt1*=0.5; dt2*=0.5;
        if (div>512) {
           cerr<<"AliV0vertexer::PropagateToDCA: overshoot !\n"; break;
        }   
     }
     dm=dd;

     t1+=dt1;
     t2+=dt2;

  }

  if (max<=0) cerr<<"AliV0vertexer::PropagateToDCA: too many iterations !\n";  
  
  //propagate tracks to the points of DCA
  Double_t cs=TMath::Cos(n->GetAlpha());
  Double_t sn=TMath::Sin(n->GetAlpha());
  Double_t x=r1[0]*cs + r1[1]*sn;
  if (!n->PropagateTo(x,0.,0.)) {
    //cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n";
    return 1.e+33;
  }  

  cs=TMath::Cos(p->GetAlpha());
  sn=TMath::Sin(p->GetAlpha());
  x=r2[0]*cs + r2[1]*sn;
  if (!p->PropagateTo(x,0.,0.)) {
    //cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n";
    return 1.e+33;
  }  

  return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
  //return TMath::Sqrt(dx*dx + dy*dy + dz*dz);
}
Commit	Line	Data
7f6ddf58	1	/**************************************************************************
	2	* Copyright(c) 1998-1999, 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	**************************************************************************/
	15
	16	//-------------------------------------------------------------------------
	17	// Implementation of the V0 vertexer class
	18	//
	19	// Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch
	20	//-------------------------------------------------------------------------
	21	#include <TFile.h>
	22	#include <TTree.h>
	23	#include <TObjArray.h>
548b1270	24	#include "Riostream.h"
7f6ddf58	25
	26	#include "AliV0vertex.h"
	27	#include "AliV0vertexer.h"
	28	#include "AliITStrackV2.h"
	29
	30	ClassImp(AliV0vertexer)
	31
	32	Int_t AliV0vertexer::Tracks2V0vertices(const TFile inp, TFile out) {
	33	//--------------------------------------------------------------------
	34	//This function reconstructs V0 vertices
	35	//--------------------------------------------------------------------
	36	TFile in=(TFile)inp;
	37	TDirectory *savedir=gDirectory;
	38
	39	if (!in->IsOpen()) {
	40	cerr<<"AliV0vertexer::Tracks2V0vertices(): ";
	41	cerr<<"file with ITS tracks has not been open !\n";
	42	return 1;
	43	}
	44
	45	if (!out->IsOpen()) {
	46	cerr<<"AliV0vertexer::Tracks2V0vertices(): ";
	47	cerr<<"file for V0 vertices has not been open !\n";
	48	return 2;
	49	}
	50
	51	in->cd();
	52
5d390eda	53	Char_t name[100];
	54	sprintf(name,"TreeT_ITS_%d",fEventN);
	55	TTree trkTree=(TTree)in->Get(name);
7f6ddf58	56	TBranch *branch=trkTree->GetBranch("tracks");
	57	Int_t nentr=(Int_t)trkTree->GetEntries();
	58
	59	TObjArray negtrks(nentr/2);
	60	TObjArray postrks(nentr/2);
	61
	62	Int_t nneg=0, npos=0, nvtx=0;
	63
	64	Int_t i;
	65	for (i=0; i<nentr; i++) {
	66	AliITStrackV2 *iotrack=new AliITStrackV2;
	67	branch->SetAddress(&iotrack);
	68	trkTree->GetEvent(i);
4ab260d6	69
	70	iotrack->PropagateTo(3.,0.0023,65.19); iotrack->PropagateTo(2.5,0.,0.);
	71
7f6ddf58	72	if (iotrack->Get1Pt() > 0.) {nneg++; negtrks.AddLast(iotrack);}
	73	else {npos++; postrks.AddLast(iotrack);}
	74	}
	75
	76
	77	out->cd();
5d390eda	78	sprintf(name,"TreeV%d",fEventN);
5d390eda	79	TTree vtxTree(name,"Tree with V0 vertices");
7f6ddf58	80	AliV0vertex *ioVertex=0;
	81	vtxTree.Branch("vertices","AliV0vertex",&ioVertex,32000,0);
	82
	83
	84	for (i=0; i<nneg; i++) {
	85	if (i%10==0) cerr<<nneg-i<<'\r';
	86	AliITStrackV2 ntrk=(AliITStrackV2 )negtrks.UncheckedAt(i);
a9a2d814	87
5d390eda	88	if (TMath::Abs(ntrk->GetD(fX,fY))<fDPmin) continue;
5d390eda	89	if (TMath::Abs(ntrk->GetD(fX,fY))>fRmax) continue;
4ab260d6	90
7f6ddf58	91	for (Int_t k=0; k<npos; k++) {
	92	AliITStrackV2 ptrk=(AliITStrackV2 )postrks.UncheckedAt(k);
	93
5d390eda	94	if (TMath::Abs(ptrk->GetD(fX,fY))<fDPmin) continue;
5d390eda	95	if (TMath::Abs(ptrk->GetD(fX,fY))>fRmax) continue;
4ab260d6	96
5d390eda	97	if (TMath::Abs(ntrk->GetD(fX,fY))<fDNmin)
5d390eda	98	if (TMath::Abs(ptrk->GetD(fX,fY))<fDNmin) continue;
4ab260d6	99
7f6ddf58	100
	101	AliITStrackV2 nt(ntrk), pt(ptrk), pnt=&nt, ppt=&pt;
	102
	103	Double_t dca=PropagateToDCA(pnt,ppt);
	104	if (dca > fDCAmax) continue;
	105
	106	AliV0vertex vertex(pnt,ppt);
	107	if (vertex.GetChi2() > fChi2max) continue;
	108
	109	/* Think of something better here !
	110	nt.PropagateToVertex(); if (TMath::Abs(nt.GetZ())<0.04) continue;
	111	pt.PropagateToVertex(); if (TMath::Abs(pt.GetZ())<0.04) continue;
	112	*/
	113
	114	Double_t x,y,z; vertex.GetXYZ(x,y,z);
	115	Double_t r2=xx + yy;
	116	if (r2 > fRmax*fRmax) continue;
	117	if (r2 < fRmin*fRmin) continue;
	118
	119	Double_t px,py,pz; vertex.GetPxPyPz(px,py,pz);
	120	Double_t p2=pxpx+pypy+pz*pz;
5d390eda	121	Double_t cost=((x-fX)px + (y-fY)py + (z-fZ)*pz)/
5d390eda	122	TMath::Sqrt(p2((x-fX)(x-fX) + (y-fY)(y-fY) + (z-fZ)(z-fZ)));
4ab260d6	123
5d390eda	124	//if (cost < (5fCPAmax-0.9-TMath::Sqrt(r2)(fCPAmax-1))/4.1) continue;
5d390eda	125	if (cost < fCPAmax) continue;
7f6ddf58	126
	127	//vertex.ChangeMassHypothesis(); //default is Lambda0
	128
	129	ioVertex=&vertex; vtxTree.Fill();
	130
	131	nvtx++;
	132	}
	133	}
	134
	135	cerr<<"Number of reconstructed V0 vertices: "<<nvtx<<endl;
	136
	137	vtxTree.Write();
	138
	139	negtrks.Delete();
	140	postrks.Delete();
	141
	142	savedir->cd();
	143
	144	delete trkTree;
	145
	146	return 0;
	147	}
	148
	149
	150	static void External2Helix(const AliITStrackV2 *t, Double_t helix[6]) {
	151	//--------------------------------------------------------------------
	152	// External track parameters -> helix parameters
	153	//--------------------------------------------------------------------
	154	Double_t alpha,x,cs,sn;
	155	t->GetExternalParameters(x,helix); alpha=t->GetAlpha();
	156
	157	cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
	158	helix[5]=xcs - helix[0]sn; // x0
	159	helix[0]=xsn + helix[0]cs; // y0
	160	//helix[1]= // z0
	161	helix[2]=TMath::ASin(helix[2]) + alpha; // phi0
	162	//helix[3]= // tgl
	163	helix[4]=helix[4]/t->GetConvConst(); // C
	164	}
	165
	166	static void Evaluate(const Double_t *h, Double_t t,
	167	Double_t r[3], //radius vector
	168	Double_t g[3], //first defivatives
	169	Double_t gg[3]) //second derivatives
	170	{
	171	//--------------------------------------------------------------------
	172	// Calculate position of a point on a track and some derivatives
	173	//--------------------------------------------------------------------
	174	Double_t phase=h[4]*t+h[2];
	175	Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
	176
	177	r[0] = h[5] + (sn - h[6])/h[4];
	178	r[1] = h[0] - (cs - h[7])/h[4];
	179	r[2] = h[1] + h[3]*t;
	180
	181	g[0] = cs; g[1]=sn; g[2]=h[3];
	182
	183	gg[0]=-h[4]sn; gg[1]=h[4]cs; gg[2]=0.;
	184	}
	185
	186	Double_t AliV0vertexer::PropagateToDCA(AliITStrackV2 n, AliITStrackV2 p) {
	187	//--------------------------------------------------------------------
	188	// This function returns the DCA between two tracks
	189	// The tracks will be moved to the point of DCA !
190	//--------------------------------------------------------------------
a9a2d814	191	Double_t dy2=n->GetSigmaY2() + p->GetSigmaY2();
	192	Double_t dz2=n->GetSigmaZ2() + p->GetSigmaZ2();
	193	Double_t dx2=dy2;
	194
	195	//dx2=dy2=dz2=1.;
	196
7f6ddf58	197	Double_t p1[8]; External2Helix(n,p1);
	198	p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
	199	Double_t p2[8]; External2Helix(p,p2);
	200	p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
	201
	202
	203	Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
	204	Evaluate(p1,t1,r1,g1,gg1);
	205	Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
	206	Evaluate(p2,t2,r2,g2,gg2);
	207
	208	Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
a9a2d814	209	Double_t dm=dxdx/dx2 + dydy/dy2 + dz*dz/dz2;
7f6ddf58	210
	211	Int_t max=27;
	212	while (max--) {
a9a2d814	213	Double_t gt1=-(dxg1[0]/dx2 + dyg1[1]/dy2 + dz*g1[2]/dz2);
	214	Double_t gt2=+(dxg2[0]/dx2 + dyg2[1]/dy2 + dz*g2[2]/dz2);
	215	Double_t h11=(g1[0]g1[0] - dxgg1[0])/dx2 +
	216	(g1[1]g1[1] - dygg1[1])/dy2 +
	217	(g1[2]g1[2] - dzgg1[2])/dz2;
	218	Double_t h22=(g2[0]g2[0] + dxgg2[0])/dx2 +
	219	(g2[1]g2[1] + dygg2[1])/dy2 +
	220	(g2[2]g2[2] + dzgg2[2])/dz2;
	221	Double_t h12=-(g1[0]g2[0]/dx2 + g1[1]g2[1]/dy2 + g1[2]*g2[2]/dz2);
7f6ddf58	222
	223	Double_t det=h11h22-h12h12;
	224
	225	Double_t dt1,dt2;
	226	if (TMath::Abs(det)<1.e-33) {
	227	//(quasi)singular Hessian
	228	dt1=-gt1; dt2=-gt2;
	229	} else {
	230	dt1=-(gt1h22 - gt2h12)/det;
	231	dt2=-(h11gt2 - h12gt1)/det;
	232	}
	233
	234	if ((dt1gt1+dt2gt2)>0) {dt1=-dt1; dt2=-dt2;}
	235
	236	//check delta(phase1) ?
	237	//check delta(phase2) ?
	238
	239	if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
	240	if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
a9a2d814	241	if ((gt1gt1+gt2gt2) > 1.e-4/dy2/dy2)
7f6ddf58	242	cerr<<"AliV0vertexer::PropagateToDCA:"
	243	" stopped at not a stationary point !\n";
	244	Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmblmb-4det);
	245	if (lmb < 0.)
	246	cerr<<"AliV0vertexer::PropagateToDCA:"
	247	" stopped at not a minimum !\n";
	248	break;
	249	}
	250
	251	Double_t dd=dm;
	252	for (Int_t div=1 ; ; div*=2) {
	253	Evaluate(p1,t1+dt1,r1,g1,gg1);
	254	Evaluate(p2,t2+dt2,r2,g2,gg2);
	255	dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
a9a2d814	256	dd=dxdx/dx2 + dydy/dy2 + dz*dz/dz2;
7f6ddf58	257	if (dd<dm) break;
	258	dt1=0.5; dt2=0.5;
	259	if (div>512) {
	260	cerr<<"AliV0vertexer::PropagateToDCA: overshoot !\n"; break;
	261	}
	262	}
	263	dm=dd;
	264
	265	t1+=dt1;
	266	t2+=dt2;
	267
	268	}
	269
	270	if (max<=0) cerr<<"AliV0vertexer::PropagateToDCA: too many iterations !\n";
	271
	272	//propagate tracks to the points of DCA
	273	Double_t cs=TMath::Cos(n->GetAlpha());
	274	Double_t sn=TMath::Sin(n->GetAlpha());
	275	Double_t x=r1[0]cs + r1[1]sn;
	276	if (!n->PropagateTo(x,0.,0.)) {
	277	//cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n";
	278	return 1.e+33;
	279	}
	280
	281	cs=TMath::Cos(p->GetAlpha());
	282	sn=TMath::Sin(p->GetAlpha());
	283	x=r2[0]cs + r2[1]sn;
	284	if (!p->PropagateTo(x,0.,0.)) {
	285	//cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n";
	286	return 1.e+33;
	287	}
	288
4ab260d6	289	return TMath::Sqrt(dmTMath::Sqrt(dy2dz2));
4ab260d6	290	//return TMath::Sqrt(dxdx + dydy + dz*dz);
7f6ddf58	291	}
	292
	293
	294
	295
	296
	297
	298
	299
	300
	301
	302
	303
	304
	305
	306
	307