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a9a2d814 | 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 cascade vertexer class | |
18 | // | |
19 | // Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr | |
20 | //------------------------------------------------------------------------- | |
116cbefd | 21 | #include <Riostream.h> |
a9a2d814 | 22 | #include <TObjArray.h> |
116cbefd | 23 | #include <TPDGCode.h> |
24 | #include <TTree.h> | |
a9a2d814 | 25 | |
26 | #include "AliCascadeVertex.h" | |
27 | #include "AliCascadeVertexer.h" | |
a9a2d814 | 28 | #include "AliITStrackV2.h" |
116cbefd | 29 | #include "AliV0vertex.h" |
a9a2d814 | 30 | |
31 | ClassImp(AliCascadeVertexer) | |
32 | ||
566abf75 | 33 | Int_t AliCascadeVertexer:: |
34 | V0sTracks2CascadeVertices(TTree *vTree,TTree *tTree, TTree *xTree) { | |
a9a2d814 | 35 | //-------------------------------------------------------------------- |
566abf75 | 36 | // This function reconstructs cascade vertices |
a9a2d814 | 37 | //-------------------------------------------------------------------- |
566abf75 | 38 | TBranch *branch=vTree->GetBranch("vertices"); |
39 | if (!branch) { | |
40 | Error("V0sTracks2CascadeVertices","Can't get the V0 branch !"); | |
41 | return 1; | |
42 | } | |
43 | Int_t nentrV0=(Int_t)vTree->GetEntries(); | |
a9a2d814 | 44 | |
45 | TObjArray vtxV0(nentrV0); | |
46 | ||
47 | // fill TObjArray vtxV0 with vertices | |
48 | ||
49 | Int_t i, nV0=0; | |
50 | for (i=0; i<nentrV0; i++) { | |
51 | ||
52 | AliV0vertex *ioVertex=new AliV0vertex; | |
53 | branch->SetAddress(&ioVertex); | |
566abf75 | 54 | vTree->GetEvent(i); |
a9a2d814 | 55 | nV0++; |
56 | vtxV0.AddLast(ioVertex); | |
57 | ||
58 | } | |
59 | ||
566abf75 | 60 | branch=tTree->GetBranch("tracks"); |
61 | if (!branch) { | |
62 | Error("V0sTracks2CascadeVertices","Can't get the track branch !"); | |
63 | return 2; | |
64 | } | |
65 | Int_t nentr=(Int_t)tTree->GetEntries(); | |
a9a2d814 | 66 | |
67 | TObjArray trks(nentr); | |
68 | ||
69 | // fill TObjArray trks with tracks | |
70 | ||
71 | Int_t ntrack=0; | |
72 | ||
73 | for (i=0; i<nentr; i++) { | |
74 | ||
75 | AliITStrackV2 *iotrack=new AliITStrackV2; | |
76 | branch->SetAddress(&iotrack); | |
566abf75 | 77 | tTree->GetEvent(i); |
4ab260d6 | 78 | |
79 | iotrack->PropagateTo(3.,0.0023,65.19); iotrack->PropagateTo(2.5,0.,0.); | |
80 | ||
a9a2d814 | 81 | ntrack++; trks.AddLast(iotrack); |
82 | ||
83 | } | |
84 | ||
566abf75 | 85 | AliCascadeVertex *ioCascade=0; |
86 | branch=xTree->GetBranch("cascades"); | |
87 | if (!branch) xTree->Branch("cascades","AliCascadeVertex",&ioCascade,32000,3); | |
88 | else branch->SetAddress(&ioCascade); | |
a9a2d814 | 89 | |
90 | // loop on all vertices | |
91 | ||
92 | Double_t massLambda=1.11568; | |
93 | Int_t ncasc=0; | |
94 | ||
95 | for (i=0; i<nV0; i++) { | |
96 | ||
97 | AliV0vertex *V0ver=(AliV0vertex *)vtxV0.UncheckedAt(i); | |
98 | ||
99 | V0ver->ChangeMassHypothesis(kLambda0); //I.B. | |
100 | ||
101 | if (V0ver->GetEffMass()<massLambda-fMassWin || // condition of the V0 mass window (cut fMassWin) | |
102 | V0ver->GetEffMass()>massLambda+fMassWin) continue; | |
103 | ||
104 | if (V0ver->GetD(0,0,0)<fDV0min) continue; // condition of minimum impact parameter of the V0 (cut fDV0min) | |
105 | // here why not cuting on pointing angle ??? | |
106 | ||
107 | // for each vertex in the good mass range, loop on all tracks (= bachelor candidates) | |
108 | ||
109 | for (Int_t k=0; k<ntrack; k++) { | |
110 | ||
111 | AliITStrackV2 *bachtrk=(AliITStrackV2 *)trks.UncheckedAt(k); | |
112 | ||
113 | if (TMath::Abs(bachtrk->GetD())<fDBachMin) continue; // eliminate to small impact parameters | |
114 | ||
115 | if (V0ver->GetPdgCode()==kLambda0 && bachtrk->Get1Pt()<0.) continue; // condition on V0 label | |
116 | if (V0ver->GetPdgCode()==kLambda0Bar && bachtrk->Get1Pt()>0.) continue; // + good sign for bachelor | |
117 | ||
118 | AliV0vertex V0(*V0ver), *pV0=&V0; | |
119 | AliITStrackV2 bt(*bachtrk), *pbt=&bt; | |
120 | ||
121 | // calculation of the distance of closest approach between the V0 and the bachelor | |
122 | ||
123 | Double_t dca=PropagateToDCA(pV0,pbt); | |
124 | if (dca > fDCAmax) continue; // cut on dca | |
125 | ||
126 | // construction of a cascade object | |
127 | ||
128 | AliCascadeVertex cascade(*pV0,*pbt); | |
129 | if (cascade.GetChi2() > fChi2max) continue; | |
130 | ||
131 | // get cascade decay position (V0, bachelor) | |
132 | ||
133 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
134 | Double_t r2=x*x + y*y; | |
135 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
136 | if (r2 < fRmin*fRmin) continue; | |
137 | ||
4ab260d6 | 138 | { |
139 | //I.B. | |
140 | Double_t x1,y1,z1; V0ver->GetXYZ(x1,y1,z1); | |
141 | if (r2 > (x1*x1+y1*y1)) continue; | |
142 | if (z*z > z1*z1) continue; | |
143 | } | |
144 | ||
a9a2d814 | 145 | // get cascade momentum |
146 | ||
147 | Double_t px,py,pz; cascade.GetPxPyPz(px,py,pz); | |
148 | Double_t p2=px*px+py*py+pz*pz; | |
149 | Double_t cost=(x*px+y*py+z*pz)/TMath::Sqrt(p2*(r2+z*z)); | |
150 | ||
151 | if (cost<fCPAmax) continue; // condition on the cascade pointing angle | |
152 | ||
153 | //cascade.ChangeMassHypothesis(); //default is Xi | |
154 | ||
155 | ||
566abf75 | 156 | ioCascade=&cascade; xTree->Fill(); |
a9a2d814 | 157 | |
158 | ncasc++; | |
159 | ||
160 | } | |
161 | } | |
162 | ||
163 | cerr<<"Number of reconstructed cascades: "<<ncasc<<endl; | |
164 | ||
a9a2d814 | 165 | trks.Delete(); |
166 | vtxV0.Delete(); | |
167 | ||
a9a2d814 | 168 | return 0; |
169 | } | |
170 | ||
171 | inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
172 | // determinant 2x2 | |
173 | return a00*a11 - a01*a10; | |
174 | } | |
175 | ||
176 | inline Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
177 | Double_t a10,Double_t a11,Double_t a12, | |
178 | Double_t a20,Double_t a21,Double_t a22) { | |
179 | // determinant 3x3 | |
180 | return | |
181 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
182 | } | |
183 | ||
184 | ||
185 | ||
186 | ||
187 | Double_t | |
188 | AliCascadeVertexer::PropagateToDCA(AliV0vertex *v, AliITStrackV2 *t) { | |
189 | //-------------------------------------------------------------------- | |
190 | // This function returns the DCA between the V0 and the track | |
191 | //-------------------------------------------------------------------- | |
192 | ||
193 | Double_t phi, x, par[5]; | |
194 | Double_t alpha, cs1, sn1; | |
195 | ||
196 | t->GetExternalParameters(x,par); alpha=t->GetAlpha(); | |
197 | phi=TMath::ASin(par[2]) + alpha; | |
198 | Double_t px1=TMath::Cos(phi), py1=TMath::Sin(phi), pz1=par[3]; | |
199 | ||
200 | ||
201 | cs1=TMath::Cos(alpha); sn1=TMath::Sin(alpha); | |
202 | Double_t x1=x*cs1 - par[0]*sn1; | |
203 | Double_t y1=x*sn1 + par[0]*cs1; | |
204 | Double_t z1=par[1]; | |
205 | ||
206 | ||
207 | Double_t x2,y2,z2; // position and momentum of V0 | |
208 | Double_t px2,py2,pz2; | |
209 | ||
210 | v->GetXYZ(x2,y2,z2); | |
211 | v->GetPxPyPz(px2,py2,pz2); | |
212 | ||
213 | // calculation dca | |
214 | ||
215 | Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2); | |
216 | Double_t ax= det(py1,pz1,py2,pz2); | |
217 | Double_t ay=-det(px1,pz1,px2,pz2); | |
218 | Double_t az= det(px1,py1,px2,py2); | |
219 | ||
220 | Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az); | |
221 | ||
222 | //points of the DCA | |
223 | Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/ | |
224 | det(px1,py1,pz1,px2,py2,pz2,ax,ay,az); | |
225 | ||
226 | x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1; | |
227 | ||
228 | ||
229 | //propagate track to the points of DCA | |
230 | ||
231 | x1=x1*cs1 + y1*sn1; | |
232 | if (!t->PropagateTo(x1,0.,0.)) { | |
233 | cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n"; | |
234 | return 1.e+33; | |
235 | } | |
236 | ||
237 | return dca; | |
238 | } | |
239 | ||
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