Coding conventions, additional comments, code clean-up (Yu.Belikov)
[u/mrichter/AliRoot.git] / ITS / AliCascadeVertexer.cxx
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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
18856a77 18// Reads V0s and tracks, writes out cascade vertices
19// Fills the ESD with the cascades
a9a2d814 20// Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr
21//-------------------------------------------------------------------------
a9a2d814 22#include <TObjArray.h>
116cbefd 23#include <TTree.h>
a9a2d814 24
e23730c7 25#include "AliESD.h"
26#include "AliESDv0.h"
a9a2d814 27#include "AliCascadeVertex.h"
28#include "AliCascadeVertexer.h"
a9a2d814 29#include "AliITStrackV2.h"
116cbefd 30#include "AliV0vertex.h"
a9a2d814 31
32ClassImp(AliCascadeVertexer)
33
e23730c7 34Int_t AliCascadeVertexer::V0sTracks2CascadeVertices(AliESD *event) {
35 //--------------------------------------------------------------------
36 // This function reconstructs cascade vertices
37 // Adapted to the ESD by I.Belikov (Jouri.Belikov@cern.ch)
38 //--------------------------------------------------------------------
39
40 Int_t nV0=(Int_t)event->GetNumberOfV0s();
41 TObjArray vtcs(nV0);
42 Int_t i;
43 for (i=0; i<nV0; i++) {
44 const AliESDv0 *esdV0=event->GetV0(i);
45 vtcs.AddLast(new AliV0vertex(*esdV0));
46 }
47
48
49 Int_t ntr=(Int_t)event->GetNumberOfTracks();
50 TObjArray trks(ntr);
51 for (i=0; i<ntr; i++) {
52 AliESDtrack *esdtr=event->GetTrack(i);
18856a77 53 Int_t status=esdtr->GetStatus();
54
55 if ((status&AliESDtrack::kITSrefit)==0)
56 if ((status&AliESDtrack::kITSout)!=0 || (status&AliESDtrack::kITSin)==0)
57 continue;
58
e23730c7 59 AliITStrackV2 *iotrack=new AliITStrackV2(*esdtr);
18856a77 60 if ((status&AliESDtrack::kITSrefit)==0) //correction for the beam pipe
61 iotrack->PropagateTo(3.,0.0023,65.19); //material
62 iotrack->PropagateTo(2.5,0.,0.);
e23730c7 63 trks.AddLast(iotrack);
64 }
65
66 Double_t massLambda=1.11568;
67 Int_t ncasc=0;
68
69 // Looking for the cascades...
70 for (i=0; i<nV0; i++) {
71 AliV0vertex *v=(AliV0vertex*)vtcs.UncheckedAt(i);
72 v->ChangeMassHypothesis(kLambda0); // the v0 must be Lambda
73 if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue;
74 if (v->GetD(0,0,0)<fDV0min) continue;
75 for (Int_t j=0; j<ntr; j++) {
76 AliITStrackV2 *b=(AliITStrackV2*)trks.UncheckedAt(j);
77
78 if (TMath::Abs(b->GetD())<fDBachMin) continue;
79 if (b->Get1Pt()<0.) continue; // bachelor's charge
80
81 AliV0vertex v0(*v), *pv0=&v0;
82 AliITStrackV2 bt(*b), *pbt=&bt;
83
84 Double_t dca=PropagateToDCA(pv0,pbt);
85 if (dca > fDCAmax) continue;
86
87 AliCascadeVertex cascade(*pv0,*pbt);
88 if (cascade.GetChi2() > fChi2max) continue;
89
90 Double_t x,y,z; cascade.GetXYZ(x,y,z);
91 Double_t r2=x*x + y*y;
92 if (r2 > fRmax*fRmax) continue; // condition on fiducial zone
93 if (r2 < fRmin*fRmin) continue;
94
95 {
96 Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1);
97 if (r2 > (x1*x1+y1*y1)) continue;
98 if (z*z > z1*z1) continue;
99 }
100
101 Double_t px,py,pz; cascade.GetPxPyPz(px,py,pz);
102 Double_t p2=px*px+py*py+pz*pz;
103 Double_t cost=(x*px+y*py+z*pz)/TMath::Sqrt(p2*(r2+z*z));
104
105 if (cost<fCPAmax) continue; //condition on the cascade pointing angle
106 //cascade.ChangeMassHypothesis(); //default is Xi
107
108 event->AddCascade(&cascade);
109
110 ncasc++;
111
112 }
113 }
114
115 // Looking for the anti-cascades...
116 for (i=0; i<nV0; i++) {
117 AliV0vertex *v=(AliV0vertex*)vtcs.UncheckedAt(i);
118 v->ChangeMassHypothesis(kLambda0Bar); //the v0 must be anti-Lambda
119 if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue;
120 if (v->GetD(0,0,0)<fDV0min) continue;
121 for (Int_t j=0; j<ntr; j++) {
122 AliITStrackV2 *b=(AliITStrackV2*)trks.UncheckedAt(j);
123
124 if (TMath::Abs(b->GetD())<fDBachMin) continue;
125 if (b->Get1Pt()>0.) continue; // bachelor's charge
126
127 AliV0vertex v0(*v), *pv0=&v0;
128 AliITStrackV2 bt(*b), *pbt=&bt;
129
130 Double_t dca=PropagateToDCA(pv0,pbt);
131 if (dca > fDCAmax) continue;
132
133 AliCascadeVertex cascade(*pv0,*pbt);
134 if (cascade.GetChi2() > fChi2max) continue;
135
136 Double_t x,y,z; cascade.GetXYZ(x,y,z);
137 Double_t r2=x*x + y*y;
138 if (r2 > fRmax*fRmax) continue; // condition on fiducial zone
139 if (r2 < fRmin*fRmin) continue;
140
141 {
142 Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1);
143 if (r2 > (x1*x1+y1*y1)) continue;
144 if (z*z > z1*z1) continue;
145 }
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 //cascade.ChangeMassHypothesis(); //default is Xi
153
154 event->AddCascade(&cascade);
155
156 ncasc++;
157
158 }
159 }
160
161Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc);
162
163 trks.Delete();
164 vtcs.Delete();
165
166 return 0;
167}
168
566abf75 169Int_t AliCascadeVertexer::
170V0sTracks2CascadeVertices(TTree *vTree,TTree *tTree, TTree *xTree) {
a9a2d814 171 //--------------------------------------------------------------------
566abf75 172 // This function reconstructs cascade vertices
a9a2d814 173 //--------------------------------------------------------------------
566abf75 174 TBranch *branch=vTree->GetBranch("vertices");
175 if (!branch) {
176 Error("V0sTracks2CascadeVertices","Can't get the V0 branch !");
177 return 1;
178 }
179 Int_t nentrV0=(Int_t)vTree->GetEntries();
a9a2d814 180
181 TObjArray vtxV0(nentrV0);
182
183 // fill TObjArray vtxV0 with vertices
184
185 Int_t i, nV0=0;
186 for (i=0; i<nentrV0; i++) {
187
188 AliV0vertex *ioVertex=new AliV0vertex;
189 branch->SetAddress(&ioVertex);
566abf75 190 vTree->GetEvent(i);
a9a2d814 191 nV0++;
192 vtxV0.AddLast(ioVertex);
193
194 }
195
566abf75 196 branch=tTree->GetBranch("tracks");
197 if (!branch) {
198 Error("V0sTracks2CascadeVertices","Can't get the track branch !");
199 return 2;
200 }
201 Int_t nentr=(Int_t)tTree->GetEntries();
a9a2d814 202
203 TObjArray trks(nentr);
204
205 // fill TObjArray trks with tracks
206
207 Int_t ntrack=0;
208
209 for (i=0; i<nentr; i++) {
210
211 AliITStrackV2 *iotrack=new AliITStrackV2;
212 branch->SetAddress(&iotrack);
566abf75 213 tTree->GetEvent(i);
4ab260d6 214
215 iotrack->PropagateTo(3.,0.0023,65.19); iotrack->PropagateTo(2.5,0.,0.);
216
a9a2d814 217 ntrack++; trks.AddLast(iotrack);
218
219 }
220
566abf75 221 AliCascadeVertex *ioCascade=0;
222 branch=xTree->GetBranch("cascades");
223 if (!branch) xTree->Branch("cascades","AliCascadeVertex",&ioCascade,32000,3);
224 else branch->SetAddress(&ioCascade);
a9a2d814 225
226 // loop on all vertices
227
228 Double_t massLambda=1.11568;
229 Int_t ncasc=0;
230
231 for (i=0; i<nV0; i++) {
232
93f82b23 233 AliV0vertex *lV0ver=(AliV0vertex *)vtxV0.UncheckedAt(i);
a9a2d814 234
93f82b23 235 lV0ver->ChangeMassHypothesis(kLambda0); //I.B.
a9a2d814 236
93f82b23 237 if (lV0ver->GetEffMass()<massLambda-fMassWin || // condition of the V0 mass window (cut fMassWin)
238 lV0ver->GetEffMass()>massLambda+fMassWin) continue;
a9a2d814 239
93f82b23 240 if (lV0ver->GetD(0,0,0)<fDV0min) continue; // condition of minimum impact parameter of the V0 (cut fDV0min)
a9a2d814 241 // here why not cuting on pointing angle ???
242
243 // for each vertex in the good mass range, loop on all tracks (= bachelor candidates)
244
245 for (Int_t k=0; k<ntrack; k++) {
246
247 AliITStrackV2 *bachtrk=(AliITStrackV2 *)trks.UncheckedAt(k);
248
249 if (TMath::Abs(bachtrk->GetD())<fDBachMin) continue; // eliminate to small impact parameters
250
93f82b23 251 if (lV0ver->GetPdgCode()==kLambda0 && bachtrk->Get1Pt()<0.) continue; // condition on V0 label
252 if (lV0ver->GetPdgCode()==kLambda0Bar && bachtrk->Get1Pt()>0.) continue; // + good sign for bachelor
a9a2d814 253
93f82b23 254 AliV0vertex lV0(*lV0ver), *pV0=&lV0;
a9a2d814 255 AliITStrackV2 bt(*bachtrk), *pbt=&bt;
256
257 // calculation of the distance of closest approach between the V0 and the bachelor
258
259 Double_t dca=PropagateToDCA(pV0,pbt);
260 if (dca > fDCAmax) continue; // cut on dca
261
262 // construction of a cascade object
263
264 AliCascadeVertex cascade(*pV0,*pbt);
265 if (cascade.GetChi2() > fChi2max) continue;
266
267 // get cascade decay position (V0, bachelor)
268
269 Double_t x,y,z; cascade.GetXYZ(x,y,z);
270 Double_t r2=x*x + y*y;
271 if (r2 > fRmax*fRmax) continue; // condition on fiducial zone
272 if (r2 < fRmin*fRmin) continue;
273
4ab260d6 274 {
275 //I.B.
93f82b23 276 Double_t x1,y1,z1; lV0ver->GetXYZ(x1,y1,z1);
4ab260d6 277 if (r2 > (x1*x1+y1*y1)) continue;
278 if (z*z > z1*z1) continue;
279 }
280
a9a2d814 281 // get cascade momentum
282
283 Double_t px,py,pz; cascade.GetPxPyPz(px,py,pz);
284 Double_t p2=px*px+py*py+pz*pz;
285 Double_t cost=(x*px+y*py+z*pz)/TMath::Sqrt(p2*(r2+z*z));
286
287 if (cost<fCPAmax) continue; // condition on the cascade pointing angle
288
289 //cascade.ChangeMassHypothesis(); //default is Xi
290
291
566abf75 292 ioCascade=&cascade; xTree->Fill();
a9a2d814 293
294 ncasc++;
295
296 }
297 }
298
e23730c7 299Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc);
a9a2d814 300
a9a2d814 301 trks.Delete();
302 vtxV0.Delete();
303
a9a2d814 304 return 0;
305}
306
307inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){
308 // determinant 2x2
309 return a00*a11 - a01*a10;
310}
311
312inline Double_t det (Double_t a00,Double_t a01,Double_t a02,
313 Double_t a10,Double_t a11,Double_t a12,
314 Double_t a20,Double_t a21,Double_t a22) {
315 // determinant 3x3
316 return
317 a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21);
318}
319
320
321
322
323Double_t
324AliCascadeVertexer::PropagateToDCA(AliV0vertex *v, AliITStrackV2 *t) {
325 //--------------------------------------------------------------------
326 // This function returns the DCA between the V0 and the track
327 //--------------------------------------------------------------------
328
329 Double_t phi, x, par[5];
330 Double_t alpha, cs1, sn1;
331
332 t->GetExternalParameters(x,par); alpha=t->GetAlpha();
333 phi=TMath::ASin(par[2]) + alpha;
334 Double_t px1=TMath::Cos(phi), py1=TMath::Sin(phi), pz1=par[3];
335
336
337 cs1=TMath::Cos(alpha); sn1=TMath::Sin(alpha);
338 Double_t x1=x*cs1 - par[0]*sn1;
339 Double_t y1=x*sn1 + par[0]*cs1;
340 Double_t z1=par[1];
341
342
343 Double_t x2,y2,z2; // position and momentum of V0
344 Double_t px2,py2,pz2;
345
346 v->GetXYZ(x2,y2,z2);
347 v->GetPxPyPz(px2,py2,pz2);
348
349// calculation dca
350
351 Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2);
352 Double_t ax= det(py1,pz1,py2,pz2);
353 Double_t ay=-det(px1,pz1,px2,pz2);
354 Double_t az= det(px1,py1,px2,py2);
355
356 Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az);
357
358//points of the DCA
359 Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/
360 det(px1,py1,pz1,px2,py2,pz2,ax,ay,az);
361
362 x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1;
363
364
365 //propagate track to the points of DCA
366
367 x1=x1*cs1 + y1*sn1;
368 if (!t->PropagateTo(x1,0.,0.)) {
e23730c7 369 Error("PropagateToDCA","Propagation failed !");
a9a2d814 370 return 1.e+33;
371 }
372
373 return dca;
374}
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