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7f6ddf58 | 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 | // | |
19 | // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch | |
20 | //------------------------------------------------------------------------- | |
21 | #include <TFile.h> | |
22 | #include <TTree.h> | |
23 | #include <TObjArray.h> | |
24 | #include <iostream.h> | |
25 | ||
26 | #include "AliV0vertex.h" | |
27 | #include "AliV0vertexer.h" | |
28 | #include "AliITStrackV2.h" | |
29 | ||
30 | ClassImp(AliV0vertexer) | |
31 | ||
32 | Int_t AliV0vertexer::Tracks2V0vertices(const TFile *inp, TFile *out) { | |
33 | //-------------------------------------------------------------------- | |
34 | //This function reconstructs V0 vertices | |
35 | //-------------------------------------------------------------------- | |
36 | TFile *in=(TFile*)inp; | |
37 | TDirectory *savedir=gDirectory; | |
38 | ||
39 | if (!in->IsOpen()) { | |
40 | cerr<<"AliV0vertexer::Tracks2V0vertices(): "; | |
41 | cerr<<"file with ITS tracks has not been open !\n"; | |
42 | return 1; | |
43 | } | |
44 | ||
45 | if (!out->IsOpen()) { | |
46 | cerr<<"AliV0vertexer::Tracks2V0vertices(): "; | |
47 | cerr<<"file for V0 vertices has not been open !\n"; | |
48 | return 2; | |
49 | } | |
50 | ||
51 | in->cd(); | |
52 | ||
53 | TTree *trkTree=(TTree*)in->Get("TreeT_ITS_0"); | |
54 | TBranch *branch=trkTree->GetBranch("tracks"); | |
55 | Int_t nentr=(Int_t)trkTree->GetEntries(); | |
56 | ||
57 | TObjArray negtrks(nentr/2); | |
58 | TObjArray postrks(nentr/2); | |
59 | ||
60 | Int_t nneg=0, npos=0, nvtx=0; | |
61 | ||
62 | Int_t i; | |
63 | for (i=0; i<nentr; i++) { | |
64 | AliITStrackV2 *iotrack=new AliITStrackV2; | |
65 | branch->SetAddress(&iotrack); | |
66 | trkTree->GetEvent(i); | |
67 | if (iotrack->Get1Pt() > 0.) {nneg++; negtrks.AddLast(iotrack);} | |
68 | else {npos++; postrks.AddLast(iotrack);} | |
69 | } | |
70 | ||
71 | ||
72 | out->cd(); | |
73 | TTree vtxTree("TreeV","Tree with V0 vertices"); | |
74 | AliV0vertex *ioVertex=0; | |
75 | vtxTree.Branch("vertices","AliV0vertex",&ioVertex,32000,0); | |
76 | ||
77 | ||
78 | for (i=0; i<nneg; i++) { | |
79 | if (i%10==0) cerr<<nneg-i<<'\r'; | |
80 | AliITStrackV2 *ntrk=(AliITStrackV2 *)negtrks.UncheckedAt(i); | |
a9a2d814 | 81 | |
7f6ddf58 | 82 | for (Int_t k=0; k<npos; k++) { |
83 | AliITStrackV2 *ptrk=(AliITStrackV2 *)postrks.UncheckedAt(k); | |
84 | ||
85 | if (TMath::Abs(ntrk->GetD())<fDNmin) continue; | |
86 | if (TMath::Abs(ptrk->GetD())<fDPmin) continue; | |
87 | ||
88 | AliITStrackV2 nt(*ntrk), pt(*ptrk), *pnt=&nt, *ppt=&pt; | |
89 | ||
90 | Double_t dca=PropagateToDCA(pnt,ppt); | |
91 | if (dca > fDCAmax) continue; | |
92 | ||
93 | AliV0vertex vertex(*pnt,*ppt); | |
94 | if (vertex.GetChi2() > fChi2max) continue; | |
95 | ||
96 | /* Think of something better here ! | |
97 | nt.PropagateToVertex(); if (TMath::Abs(nt.GetZ())<0.04) continue; | |
98 | pt.PropagateToVertex(); if (TMath::Abs(pt.GetZ())<0.04) continue; | |
99 | */ | |
100 | ||
101 | Double_t x,y,z; vertex.GetXYZ(x,y,z); | |
102 | Double_t r2=x*x + y*y; | |
103 | if (r2 > fRmax*fRmax) continue; | |
104 | if (r2 < fRmin*fRmin) continue; | |
105 | ||
106 | Double_t px,py,pz; vertex.GetPxPyPz(px,py,pz); | |
107 | Double_t p2=px*px+py*py+pz*pz; | |
108 | Double_t cost=(x*px+y*py+z*pz)/TMath::Sqrt(p2*(r2+z*z)); | |
109 | if (cost<fCPAmax) continue; | |
110 | ||
111 | //vertex.ChangeMassHypothesis(); //default is Lambda0 | |
112 | ||
113 | ioVertex=&vertex; vtxTree.Fill(); | |
114 | ||
115 | nvtx++; | |
116 | } | |
117 | } | |
118 | ||
119 | cerr<<"Number of reconstructed V0 vertices: "<<nvtx<<endl; | |
120 | ||
121 | vtxTree.Write(); | |
122 | ||
123 | negtrks.Delete(); | |
124 | postrks.Delete(); | |
125 | ||
126 | savedir->cd(); | |
127 | ||
128 | delete trkTree; | |
129 | ||
130 | return 0; | |
131 | } | |
132 | ||
133 | ||
134 | static void External2Helix(const AliITStrackV2 *t, Double_t helix[6]) { | |
135 | //-------------------------------------------------------------------- | |
136 | // External track parameters -> helix parameters | |
137 | //-------------------------------------------------------------------- | |
138 | Double_t alpha,x,cs,sn; | |
139 | t->GetExternalParameters(x,helix); alpha=t->GetAlpha(); | |
140 | ||
141 | cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); | |
142 | helix[5]=x*cs - helix[0]*sn; // x0 | |
143 | helix[0]=x*sn + helix[0]*cs; // y0 | |
144 | //helix[1]= // z0 | |
145 | helix[2]=TMath::ASin(helix[2]) + alpha; // phi0 | |
146 | //helix[3]= // tgl | |
147 | helix[4]=helix[4]/t->GetConvConst(); // C | |
148 | } | |
149 | ||
150 | static void Evaluate(const Double_t *h, Double_t t, | |
151 | Double_t r[3], //radius vector | |
152 | Double_t g[3], //first defivatives | |
153 | Double_t gg[3]) //second derivatives | |
154 | { | |
155 | //-------------------------------------------------------------------- | |
156 | // Calculate position of a point on a track and some derivatives | |
157 | //-------------------------------------------------------------------- | |
158 | Double_t phase=h[4]*t+h[2]; | |
159 | Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase); | |
160 | ||
161 | r[0] = h[5] + (sn - h[6])/h[4]; | |
162 | r[1] = h[0] - (cs - h[7])/h[4]; | |
163 | r[2] = h[1] + h[3]*t; | |
164 | ||
165 | g[0] = cs; g[1]=sn; g[2]=h[3]; | |
166 | ||
167 | gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.; | |
168 | } | |
169 | ||
170 | Double_t AliV0vertexer::PropagateToDCA(AliITStrackV2 *n, AliITStrackV2 *p) { | |
171 | //-------------------------------------------------------------------- | |
172 | // This function returns the DCA between two tracks | |
173 | // The tracks will be moved to the point of DCA ! | |
174 | //-------------------------------------------------------------------- | |
a9a2d814 | 175 | Double_t dy2=n->GetSigmaY2() + p->GetSigmaY2(); |
176 | Double_t dz2=n->GetSigmaZ2() + p->GetSigmaZ2(); | |
177 | Double_t dx2=dy2; | |
178 | ||
179 | //dx2=dy2=dz2=1.; | |
180 | ||
7f6ddf58 | 181 | Double_t p1[8]; External2Helix(n,p1); |
182 | p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]); | |
183 | Double_t p2[8]; External2Helix(p,p2); | |
184 | p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]); | |
185 | ||
186 | ||
187 | Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.; | |
188 | Evaluate(p1,t1,r1,g1,gg1); | |
189 | Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.; | |
190 | Evaluate(p2,t2,r2,g2,gg2); | |
191 | ||
192 | Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2]; | |
a9a2d814 | 193 | Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2; |
7f6ddf58 | 194 | |
195 | Int_t max=27; | |
196 | while (max--) { | |
a9a2d814 | 197 | Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2); |
198 | Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2); | |
199 | Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 + | |
200 | (g1[1]*g1[1] - dy*gg1[1])/dy2 + | |
201 | (g1[2]*g1[2] - dz*gg1[2])/dz2; | |
202 | Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 + | |
203 | (g2[1]*g2[1] + dy*gg2[1])/dy2 + | |
204 | (g2[2]*g2[2] + dz*gg2[2])/dz2; | |
205 | Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2); | |
7f6ddf58 | 206 | |
207 | Double_t det=h11*h22-h12*h12; | |
208 | ||
209 | Double_t dt1,dt2; | |
210 | if (TMath::Abs(det)<1.e-33) { | |
211 | //(quasi)singular Hessian | |
212 | dt1=-gt1; dt2=-gt2; | |
213 | } else { | |
214 | dt1=-(gt1*h22 - gt2*h12)/det; | |
215 | dt2=-(h11*gt2 - h12*gt1)/det; | |
216 | } | |
217 | ||
218 | if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;} | |
219 | ||
220 | //check delta(phase1) ? | |
221 | //check delta(phase2) ? | |
222 | ||
223 | if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4) | |
224 | if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) { | |
a9a2d814 | 225 | if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2) |
7f6ddf58 | 226 | cerr<<"AliV0vertexer::PropagateToDCA:" |
227 | " stopped at not a stationary point !\n"; | |
228 | Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det); | |
229 | if (lmb < 0.) | |
230 | cerr<<"AliV0vertexer::PropagateToDCA:" | |
231 | " stopped at not a minimum !\n"; | |
232 | break; | |
233 | } | |
234 | ||
235 | Double_t dd=dm; | |
236 | for (Int_t div=1 ; ; div*=2) { | |
237 | Evaluate(p1,t1+dt1,r1,g1,gg1); | |
238 | Evaluate(p2,t2+dt2,r2,g2,gg2); | |
239 | dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2]; | |
a9a2d814 | 240 | dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2; |
7f6ddf58 | 241 | if (dd<dm) break; |
242 | dt1*=0.5; dt2*=0.5; | |
243 | if (div>512) { | |
244 | cerr<<"AliV0vertexer::PropagateToDCA: overshoot !\n"; break; | |
245 | } | |
246 | } | |
247 | dm=dd; | |
248 | ||
249 | t1+=dt1; | |
250 | t2+=dt2; | |
251 | ||
252 | } | |
253 | ||
254 | if (max<=0) cerr<<"AliV0vertexer::PropagateToDCA: too many iterations !\n"; | |
255 | ||
256 | //propagate tracks to the points of DCA | |
257 | Double_t cs=TMath::Cos(n->GetAlpha()); | |
258 | Double_t sn=TMath::Sin(n->GetAlpha()); | |
259 | Double_t x=r1[0]*cs + r1[1]*sn; | |
260 | if (!n->PropagateTo(x,0.,0.)) { | |
261 | //cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n"; | |
262 | return 1.e+33; | |
263 | } | |
264 | ||
265 | cs=TMath::Cos(p->GetAlpha()); | |
266 | sn=TMath::Sin(p->GetAlpha()); | |
267 | x=r2[0]*cs + r2[1]*sn; | |
268 | if (!p->PropagateTo(x,0.,0.)) { | |
269 | //cerr<<"AliV0vertexer::PropagateToDCA: propagation failed !\n"; | |
270 | return 1.e+33; | |
271 | } | |
272 | ||
a9a2d814 | 273 | //return TMath::Sqrt(dm); |
274 | return TMath::Sqrt(dx*dx + dy*dy + dz*dz); | |
7f6ddf58 | 275 | } |
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