Looser default cuts for the V0 and the cascade finders
[u/mrichter/AliRoot.git] / STEER / AliV0vertexer.cxx
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c7bafca9 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// reads tracks writes out V0 vertices
19// fills the ESD with the V0s
8859d205 20// Origin: Iouri Belikov, IPHC, Strasbourg, Jouri.Belikov@cern.ch
c7bafca9 21//-------------------------------------------------------------------------
c028b974 22
23
af885e0f 24#include "AliESDEvent.h"
c7bafca9 25#include "AliESDv0.h"
c7bafca9 26#include "AliV0vertexer.h"
27
28ClassImp(AliV0vertexer)
29
5e4ff34d 30
31//A set of very loose cuts
e82eee7e 32Double_t AliV0vertexer::fgChi2max=33.; //max chi2
33Double_t AliV0vertexer::fgDNmin=0.05; //min imp parameter for the 1st daughter
34Double_t AliV0vertexer::fgDPmin=0.05; //min imp parameter for the 2nd daughter
9fbe5c5c 35Double_t AliV0vertexer::fgDCAmax=1.5; //max DCA between the daughter tracks
36Double_t AliV0vertexer::fgCPAmin=0.9; //min cosine of V0's pointing angle
e82eee7e 37Double_t AliV0vertexer::fgRmin=0.2; //min radius of the fiducial volume
38Double_t AliV0vertexer::fgRmax=100.; //max radius of the fiducial volume
5e4ff34d 39
af885e0f 40Int_t AliV0vertexer::Tracks2V0vertices(AliESDEvent *event) {
c7bafca9 41 //--------------------------------------------------------------------
42 //This function reconstructs V0 vertices
43 //--------------------------------------------------------------------
8859d205 44
8859d205 45 const AliESDVertex *vtxT3D=event->GetPrimaryVertex();
46
69c49ae1 47 Double_t xPrimaryVertex=vtxT3D->GetXv();
48 Double_t yPrimaryVertex=vtxT3D->GetYv();
49 Double_t zPrimaryVertex=vtxT3D->GetZv();
c7bafca9 50
51 Int_t nentr=event->GetNumberOfTracks();
52 Double_t b=event->GetMagneticField();
53
da46f3ca 54 if (nentr<2) return 0;
55
1684b2ce 56 TArrayI neg(nentr);
57 TArrayI pos(nentr);
c7bafca9 58
59 Int_t nneg=0, npos=0, nvtx=0;
60
61 Int_t i;
62 for (i=0; i<nentr; i++) {
63 AliESDtrack *esdTrack=event->GetTrack(i);
46be1d8a 64 ULong_t status=esdTrack->GetStatus();
c7bafca9 65
66 if ((status&AliESDtrack::kITSrefit)==0)
46be1d8a 67 if ((status&AliESDtrack::kTPCrefit)==0) continue;
c7bafca9 68
8859d205 69 Double_t d=esdTrack->GetD(xPrimaryVertex,yPrimaryVertex,b);
c7bafca9 70 if (TMath::Abs(d)<fDPmin) continue;
71 if (TMath::Abs(d)>fRmax) continue;
72
73 if (esdTrack->GetSign() < 0.) neg[nneg++]=i;
74 else pos[npos++]=i;
75 }
76
77
78 for (i=0; i<nneg; i++) {
79 Int_t nidx=neg[i];
80 AliESDtrack *ntrk=event->GetTrack(nidx);
81
82 for (Int_t k=0; k<npos; k++) {
83 Int_t pidx=pos[k];
84 AliESDtrack *ptrk=event->GetTrack(pidx);
85
8859d205 86 if (TMath::Abs(ntrk->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDNmin)
87 if (TMath::Abs(ptrk->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDNmin) continue;
c7bafca9 88
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;
93
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
98 corrected=kTRUE;
99 }
100 if ((pt.GetX() > 3.) && (xp < 3.)) {
101 //correct for the beam pipe material
102 corrected=kTRUE;
103 }
104 if (corrected) {
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;
109 }
110
111 nt.PropagateTo(xn,b); pt.PropagateTo(xp,b);
112
113 AliESDv0 vertex(nt,nidx,pt,pidx);
c028b974 114 if (vertex.GetChi2V0() > fChi2max) continue;
c7bafca9 115
8859d205 116 Float_t cpa=vertex.GetV0CosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex);
46be1d8a 117 if (cpa < fCPAmin) continue;
c028b974 118 vertex.SetDcaV0Daughters(dca);
b75d63a7 119 vertex.SetV0CosineOfPointingAngle(cpa);
120 vertex.ChangeMassHypothesis(kK0Short);
c7bafca9 121
122 event->AddV0(&vertex);
123
124 nvtx++;
125 }
126 }
127
128 Info("Tracks2V0vertices","Number of reconstructed V0 vertices: %d",nvtx);
129
da46f3ca 130 return nvtx;
c7bafca9 131}
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