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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 | //------------------------------------------------------------------------- | |
21 | #include <TFile.h> | |
22 | #include <TTree.h> | |
23 | #include <TObjArray.h> | |
24 | #include <iostream.h> | |
25 | ||
26 | #include "AliCascadeVertex.h" | |
27 | #include "AliCascadeVertexer.h" | |
28 | #include "AliV0vertex.h" | |
29 | #include "AliITStrackV2.h" | |
30 | ||
31 | ClassImp(AliCascadeVertexer) | |
32 | ||
33 | Int_t | |
34 | AliCascadeVertexer::V0sTracks2CascadeVertices(const TFile *inp, TFile *out) { | |
35 | ||
36 | //-------------------------------------------------------------------- | |
37 | //This function reconstructs cascade vertices | |
38 | //-------------------------------------------------------------------- | |
39 | TFile *in=(TFile*)inp; | |
40 | TDirectory *savedir=gDirectory; | |
41 | ||
42 | // Tree for vertices(V0's) | |
43 | ||
44 | TTree *vtxTree=(TTree*)gDirectory->Get("TreeV"); | |
45 | TBranch *branch=vtxTree->GetBranch("vertices"); | |
46 | Int_t nentrV0=(Int_t)vtxTree->GetEntries(); | |
47 | ||
48 | TObjArray vtxV0(nentrV0); | |
49 | ||
50 | // fill TObjArray vtxV0 with vertices | |
51 | ||
52 | Int_t i, nV0=0; | |
53 | for (i=0; i<nentrV0; i++) { | |
54 | ||
55 | AliV0vertex *ioVertex=new AliV0vertex; | |
56 | branch->SetAddress(&ioVertex); | |
57 | vtxTree->GetEvent(i); | |
58 | nV0++; | |
59 | vtxV0.AddLast(ioVertex); | |
60 | ||
61 | } | |
62 | ||
63 | ||
64 | in->cd(); | |
65 | ||
66 | // Tree for tracks | |
67 | ||
68 | TTree *trkTree=(TTree*)in->Get("TreeT_ITS_0"); | |
69 | branch=trkTree->GetBranch("tracks"); | |
70 | Int_t nentr=(Int_t)trkTree->GetEntries(); | |
71 | ||
72 | TObjArray trks(nentr); | |
73 | ||
74 | // fill TObjArray trks with tracks | |
75 | ||
76 | Int_t ntrack=0; | |
77 | ||
78 | for (i=0; i<nentr; i++) { | |
79 | ||
80 | AliITStrackV2 *iotrack=new AliITStrackV2; | |
81 | branch->SetAddress(&iotrack); | |
82 | trkTree->GetEvent(i); | |
83 | ntrack++; trks.AddLast(iotrack); | |
84 | ||
85 | } | |
86 | ||
87 | // create Tree for cascades | |
88 | ||
89 | out->cd(); | |
90 | ||
91 | TTree cascTree("TreeCasc","Tree with cascades"); | |
92 | AliCascadeVertex *ioCascade=0; | |
93 | cascTree.Branch("cascades","AliCascadeVertex",&ioCascade,32000,0); | |
94 | ||
95 | // loop on all vertices | |
96 | ||
97 | Double_t massLambda=1.11568; | |
98 | Int_t ncasc=0; | |
99 | ||
100 | for (i=0; i<nV0; i++) { | |
101 | ||
102 | AliV0vertex *V0ver=(AliV0vertex *)vtxV0.UncheckedAt(i); | |
103 | ||
104 | V0ver->ChangeMassHypothesis(kLambda0); //I.B. | |
105 | ||
106 | if (V0ver->GetEffMass()<massLambda-fMassWin || // condition of the V0 mass window (cut fMassWin) | |
107 | V0ver->GetEffMass()>massLambda+fMassWin) continue; | |
108 | ||
109 | if (V0ver->GetD(0,0,0)<fDV0min) continue; // condition of minimum impact parameter of the V0 (cut fDV0min) | |
110 | // here why not cuting on pointing angle ??? | |
111 | ||
112 | // for each vertex in the good mass range, loop on all tracks (= bachelor candidates) | |
113 | ||
114 | for (Int_t k=0; k<ntrack; k++) { | |
115 | ||
116 | AliITStrackV2 *bachtrk=(AliITStrackV2 *)trks.UncheckedAt(k); | |
117 | ||
118 | if (TMath::Abs(bachtrk->GetD())<fDBachMin) continue; // eliminate to small impact parameters | |
119 | ||
120 | if (V0ver->GetPdgCode()==kLambda0 && bachtrk->Get1Pt()<0.) continue; // condition on V0 label | |
121 | if (V0ver->GetPdgCode()==kLambda0Bar && bachtrk->Get1Pt()>0.) continue; // + good sign for bachelor | |
122 | ||
123 | AliV0vertex V0(*V0ver), *pV0=&V0; | |
124 | AliITStrackV2 bt(*bachtrk), *pbt=&bt; | |
125 | ||
126 | // calculation of the distance of closest approach between the V0 and the bachelor | |
127 | ||
128 | Double_t dca=PropagateToDCA(pV0,pbt); | |
129 | if (dca > fDCAmax) continue; // cut on dca | |
130 | ||
131 | // construction of a cascade object | |
132 | ||
133 | AliCascadeVertex cascade(*pV0,*pbt); | |
134 | if (cascade.GetChi2() > fChi2max) continue; | |
135 | ||
136 | // get cascade decay position (V0, bachelor) | |
137 | ||
138 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
139 | Double_t r2=x*x + y*y; | |
140 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
141 | if (r2 < fRmin*fRmin) continue; | |
142 | ||
143 | // get cascade momentum | |
144 | ||
145 | Double_t px,py,pz; cascade.GetPxPyPz(px,py,pz); | |
146 | Double_t p2=px*px+py*py+pz*pz; | |
147 | Double_t cost=(x*px+y*py+z*pz)/TMath::Sqrt(p2*(r2+z*z)); | |
148 | ||
149 | if (cost<fCPAmax) continue; // condition on the cascade pointing angle | |
150 | ||
151 | //cascade.ChangeMassHypothesis(); //default is Xi | |
152 | ||
153 | ||
154 | ioCascade=&cascade; cascTree.Fill(); | |
155 | ||
156 | ncasc++; | |
157 | ||
158 | } | |
159 | } | |
160 | ||
161 | cerr<<"Number of reconstructed cascades: "<<ncasc<<endl; | |
162 | ||
163 | cascTree.Write(); | |
164 | ||
165 | trks.Delete(); | |
166 | vtxV0.Delete(); | |
167 | ||
168 | savedir->cd(); | |
169 | ||
170 | return 0; | |
171 | } | |
172 | ||
173 | inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
174 | // determinant 2x2 | |
175 | return a00*a11 - a01*a10; | |
176 | } | |
177 | ||
178 | inline Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
179 | Double_t a10,Double_t a11,Double_t a12, | |
180 | Double_t a20,Double_t a21,Double_t a22) { | |
181 | // determinant 3x3 | |
182 | return | |
183 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
184 | } | |
185 | ||
186 | ||
187 | ||
188 | ||
189 | Double_t | |
190 | AliCascadeVertexer::PropagateToDCA(AliV0vertex *v, AliITStrackV2 *t) { | |
191 | //-------------------------------------------------------------------- | |
192 | // This function returns the DCA between the V0 and the track | |
193 | //-------------------------------------------------------------------- | |
194 | ||
195 | Double_t phi, x, par[5]; | |
196 | Double_t alpha, cs1, sn1; | |
197 | ||
198 | t->GetExternalParameters(x,par); alpha=t->GetAlpha(); | |
199 | phi=TMath::ASin(par[2]) + alpha; | |
200 | Double_t px1=TMath::Cos(phi), py1=TMath::Sin(phi), pz1=par[3]; | |
201 | ||
202 | ||
203 | cs1=TMath::Cos(alpha); sn1=TMath::Sin(alpha); | |
204 | Double_t x1=x*cs1 - par[0]*sn1; | |
205 | Double_t y1=x*sn1 + par[0]*cs1; | |
206 | Double_t z1=par[1]; | |
207 | ||
208 | ||
209 | Double_t x2,y2,z2; // position and momentum of V0 | |
210 | Double_t px2,py2,pz2; | |
211 | ||
212 | v->GetXYZ(x2,y2,z2); | |
213 | v->GetPxPyPz(px2,py2,pz2); | |
214 | ||
215 | // calculation dca | |
216 | ||
217 | Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2); | |
218 | Double_t ax= det(py1,pz1,py2,pz2); | |
219 | Double_t ay=-det(px1,pz1,px2,pz2); | |
220 | Double_t az= det(px1,py1,px2,py2); | |
221 | ||
222 | Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az); | |
223 | ||
224 | //points of the DCA | |
225 | Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/ | |
226 | det(px1,py1,pz1,px2,py2,pz2,ax,ay,az); | |
227 | ||
228 | x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1; | |
229 | ||
230 | ||
231 | //propagate track to the points of DCA | |
232 | ||
233 | x1=x1*cs1 + y1*sn1; | |
234 | if (!t->PropagateTo(x1,0.,0.)) { | |
235 | cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n"; | |
236 | return 1.e+33; | |
237 | } | |
238 | ||
239 | return dca; | |
240 | } | |
241 | ||
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