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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 | |
20 | // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch | |
21 | //------------------------------------------------------------------------- | |
22 | ||
23 | ||
24 | #include <TObjArray.h> | |
25 | #include <TTree.h> | |
26 | ||
27 | #include "AliESD.h" | |
28 | #include "AliESDv0.h" | |
29 | #include "AliESDtrack.h" | |
30 | #include "AliV0vertexer.h" | |
31 | ||
32 | ClassImp(AliV0vertexer) | |
33 | ||
34 | ||
35 | //A set of very loose cuts | |
36 | Double_t AliV0vertexer::fgChi2max=33.; //max chi2 | |
37 | Double_t AliV0vertexer::fgDNmin=0.05; //min imp parameter for the 1st daughter | |
38 | Double_t AliV0vertexer::fgDPmin=0.05; //min imp parameter for the 2nd daughter | |
39 | Double_t AliV0vertexer::fgDCAmax=0.5; //max DCA between the daughter tracks | |
40 | Double_t AliV0vertexer::fgCPAmax=0.99; //max cosine of V0's pointing angle | |
41 | Double_t AliV0vertexer::fgRmin=0.2; //min radius of the fiducial volume | |
42 | Double_t AliV0vertexer::fgRmax=100.; //max radius of the fiducial volume | |
43 | ||
44 | Int_t AliV0vertexer::Tracks2V0vertices(AliESD *event) { | |
45 | //-------------------------------------------------------------------- | |
46 | //This function reconstructs V0 vertices | |
47 | //-------------------------------------------------------------------- | |
48 | const AliESDVertex *vtx=event->GetVertex(); | |
49 | Double_t xv=vtx->GetXv(), yv=vtx->GetYv(), zv=vtx->GetZv(); | |
50 | ||
51 | Int_t nentr=event->GetNumberOfTracks(); | |
52 | Double_t b=event->GetMagneticField(); | |
53 | ||
54 | if (nentr<2) return 0; | |
55 | ||
56 | TArrayI neg(nentr/2); | |
57 | TArrayI pos(nentr/2); | |
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); | |
64 | UInt_t status=esdTrack->GetStatus(); | |
65 | UInt_t flags=AliESDtrack::kITSin|AliESDtrack::kTPCin| | |
66 | AliESDtrack::kTPCpid|AliESDtrack::kESDpid; | |
67 | ||
68 | if ((status&AliESDtrack::kITSrefit)==0) | |
69 | if (flags!=status) continue; | |
70 | ||
71 | Double_t d=esdTrack->GetD(xv,yv,b); | |
72 | if (TMath::Abs(d)<fDPmin) continue; | |
73 | if (TMath::Abs(d)>fRmax) continue; | |
74 | ||
75 | if (esdTrack->GetSign() < 0.) neg[nneg++]=i; | |
76 | else pos[npos++]=i; | |
77 | } | |
78 | ||
79 | ||
80 | for (i=0; i<nneg; i++) { | |
81 | Int_t nidx=neg[i]; | |
82 | AliESDtrack *ntrk=event->GetTrack(nidx); | |
83 | ||
84 | for (Int_t k=0; k<npos; k++) { | |
85 | Int_t pidx=pos[k]; | |
86 | AliESDtrack *ptrk=event->GetTrack(pidx); | |
87 | ||
88 | if (TMath::Abs(ntrk->GetD(xv,yv,b))<fDNmin) | |
89 | if (TMath::Abs(ptrk->GetD(xv,yv,b))<fDNmin) continue; | |
90 | ||
91 | Double_t xn, xp, dca=ntrk->GetDCA(ptrk,b,xn,xp); | |
92 | if (dca > fDCAmax) continue; | |
93 | if ((xn+xp) > 2*fRmax) continue; | |
94 | if ((xn+xp) < 2*fRmin) continue; | |
95 | ||
96 | AliExternalTrackParam nt(*ntrk), pt(*ptrk); | |
97 | Bool_t corrected=kFALSE; | |
98 | if ((nt.GetX() > 3.) && (xn < 3.)) { | |
99 | //correct for the beam pipe material | |
100 | corrected=kTRUE; | |
101 | } | |
102 | if ((pt.GetX() > 3.) && (xp < 3.)) { | |
103 | //correct for the beam pipe material | |
104 | corrected=kTRUE; | |
105 | } | |
106 | if (corrected) { | |
107 | dca=nt.GetDCA(&pt,b,xn,xp); | |
108 | if (dca > fDCAmax) continue; | |
109 | if ((xn+xp) > 2*fRmax) continue; | |
110 | if ((xn+xp) < 2*fRmin) continue; | |
111 | } | |
112 | ||
113 | nt.PropagateTo(xn,b); pt.PropagateTo(xp,b); | |
114 | ||
115 | AliESDv0 vertex(nt,nidx,pt,pidx); | |
116 | if (vertex.GetChi2V0() > fChi2max) continue; | |
117 | ||
118 | Float_t cpa=vertex.GetV0CosineOfPointingAngle(xv,yv,zv); | |
119 | if (cpa < fCPAmax) continue; | |
120 | vertex.SetDcaV0Daughters(dca); | |
121 | vertex.SetV0CosineOfPointingAngle(cpa); | |
122 | vertex.ChangeMassHypothesis(kK0Short); | |
123 | ||
124 | event->AddV0(&vertex); | |
125 | ||
126 | nvtx++; | |
127 | } | |
128 | } | |
129 | ||
130 | Info("Tracks2V0vertices","Number of reconstructed V0 vertices: %d",nvtx); | |
131 | ||
132 | return nvtx; | |
133 | } | |
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