1 /**************************************************************************
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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
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14 **************************************************************************/
16 //-------------------------------------------------------------------------
17 // Implementation of the V0 vertexer class
18 // reads tracks writes out V0 vertices
19 // fills the ESD with the V0s
20 // Origin: Iouri Belikov, IPHC, Strasbourg, Jouri.Belikov@cern.ch
21 //-------------------------------------------------------------------------
24 #include "AliESDEvent.h"
26 #include "AliV0vertexer.h"
28 ClassImp(AliV0vertexer)
31 //A set of very loose cuts
32 Double_t AliV0vertexer::fgChi2max=33.; //max chi2
33 Double_t AliV0vertexer::fgDNmin=0.05; //min imp parameter for the 1st daughter
34 Double_t AliV0vertexer::fgDPmin=0.05; //min imp parameter for the 2nd daughter
35 Double_t AliV0vertexer::fgDCAmax=0.5; //max DCA between the daughter tracks
36 Double_t AliV0vertexer::fgCPAmin=0.99; //min cosine of V0's pointing angle
37 Double_t AliV0vertexer::fgRmin=0.2; //min radius of the fiducial volume
38 Double_t AliV0vertexer::fgRmax=100.; //max radius of the fiducial volume
40 Int_t AliV0vertexer::Tracks2V0vertices(AliESDEvent *event) {
41 //--------------------------------------------------------------------
42 //This function reconstructs V0 vertices
43 //--------------------------------------------------------------------
45 const AliESDVertex *vtxT3D=event->GetPrimaryVertex();
47 Double_t xPrimaryVertex=vtxT3D->GetXv();
48 Double_t yPrimaryVertex=vtxT3D->GetYv();
49 Double_t zPrimaryVertex=vtxT3D->GetZv();
51 Int_t nentr=event->GetNumberOfTracks();
52 Double_t b=event->GetMagneticField();
54 if (nentr<2) return 0;
59 Int_t nneg=0, npos=0, nvtx=0;
62 for (i=0; i<nentr; i++) {
63 AliESDtrack *esdTrack=event->GetTrack(i);
64 ULong_t status=esdTrack->GetStatus();
66 if ((status&AliESDtrack::kITSrefit)==0)
67 if ((status&AliESDtrack::kTPCrefit)==0) continue;
69 Double_t d=esdTrack->GetD(xPrimaryVertex,yPrimaryVertex,b);
70 if (TMath::Abs(d)<fDPmin) continue;
71 if (TMath::Abs(d)>fRmax) continue;
73 if (esdTrack->GetSign() < 0.) neg[nneg++]=i;
78 for (i=0; i<nneg; i++) {
80 AliESDtrack *ntrk=event->GetTrack(nidx);
82 for (Int_t k=0; k<npos; k++) {
84 AliESDtrack *ptrk=event->GetTrack(pidx);
86 if (TMath::Abs(ntrk->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDNmin)
87 if (TMath::Abs(ptrk->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDNmin) continue;
89 Double_t xn, xp, dca=ntrk->GetDCA(ptrk,b,xn,xp);
90 if (dca > fDCAmax) continue;
91 if ((xn+xp) > 2*fRmax) continue;
92 if ((xn+xp) < 2*fRmin) continue;
94 AliExternalTrackParam nt(*ntrk), pt(*ptrk);
95 Bool_t corrected=kFALSE;
96 if ((nt.GetX() > 3.) && (xn < 3.)) {
97 //correct for the beam pipe material
100 if ((pt.GetX() > 3.) && (xp < 3.)) {
101 //correct for the beam pipe material
105 dca=nt.GetDCA(&pt,b,xn,xp);
106 if (dca > fDCAmax) continue;
107 if ((xn+xp) > 2*fRmax) continue;
108 if ((xn+xp) < 2*fRmin) continue;
111 nt.PropagateTo(xn,b); pt.PropagateTo(xp,b);
113 AliESDv0 vertex(nt,nidx,pt,pidx);
114 if (vertex.GetChi2V0() > fChi2max) continue;
116 Float_t cpa=vertex.GetV0CosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex);
117 if (cpa < fCPAmin) continue;
118 vertex.SetDcaV0Daughters(dca);
119 vertex.SetV0CosineOfPointingAngle(cpa);
120 vertex.ChangeMassHypothesis(kK0Short);
122 event->AddV0(&vertex);
128 Info("Tracks2V0vertices","Number of reconstructed V0 vertices: %d",nvtx);