Updated code for tracking V2 (from Y. Belikov)
[u/mrichter/AliRoot.git] / ITS / AliV0vertexer.cxx
CommitLineData
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
30ClassImp(AliV0vertexer)
31
32Int_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
134static 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
150static 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
170Double_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}
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291