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c7bafca9 | 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 | // Reads V0s and tracks, writes out cascade vertices | |
19 | // Fills the ESD with the cascades | |
20 | // Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr | |
21 | //------------------------------------------------------------------------- | |
c028b974 | 22 | |
23 | //modified by R. Vernet 30/6/2006 : daughter label | |
24 | //modified by R. Vernet 3/7/2006 : causality | |
25 | ||
26 | ||
c7bafca9 | 27 | #include <TObjArray.h> |
28 | #include <TTree.h> | |
29 | ||
30 | #include "AliESD.h" | |
31 | #include "AliESDv0.h" | |
32 | #include "AliESDcascade.h" | |
33 | #include "AliCascadeVertexer.h" | |
34 | ||
35 | ClassImp(AliCascadeVertexer) | |
36 | ||
37 | Int_t AliCascadeVertexer::V0sTracks2CascadeVertices(AliESD *event) { | |
38 | //-------------------------------------------------------------------- | |
39 | // This function reconstructs cascade vertices | |
40 | // Adapted to the ESD by I.Belikov (Jouri.Belikov@cern.ch) | |
41 | //-------------------------------------------------------------------- | |
42 | Double_t b=event->GetMagneticField(); | |
43 | Int_t nV0=(Int_t)event->GetNumberOfV0s(); | |
c028b974 | 44 | |
45 | //stores relevant V0s in an array | |
c7bafca9 | 46 | TObjArray vtcs(nV0); |
47 | Int_t i; | |
48 | for (i=0; i<nV0; i++) { | |
49 | AliESDv0 *v=event->GetV0(i); | |
d6a49f20 | 50 | if (v->GetOnFlyStatus()) continue; |
c7bafca9 | 51 | if (v->GetD(fX,fY,fZ)<fDV0min) continue; |
52 | vtcs.AddLast(v); | |
53 | } | |
54 | nV0=vtcs.GetEntriesFast(); | |
55 | ||
c028b974 | 56 | // stores relevant tracks in another array |
c7bafca9 | 57 | Int_t nentr=(Int_t)event->GetNumberOfTracks(); |
58 | TArrayI trk(nentr); Int_t ntr=0; | |
59 | for (i=0; i<nentr; i++) { | |
60 | AliESDtrack *esdtr=event->GetTrack(i); | |
61 | UInt_t status=esdtr->GetStatus(); | |
62 | UInt_t flags=AliESDtrack::kITSin|AliESDtrack::kTPCin| | |
63 | AliESDtrack::kTPCpid|AliESDtrack::kESDpid; | |
64 | ||
65 | if ((status&AliESDtrack::kITSrefit)==0) | |
66 | if (flags!=status) continue; | |
67 | ||
68 | if (TMath::Abs(esdtr->GetD(fX,fY,b))<fDBachMin) continue; | |
69 | ||
70 | trk[ntr++]=i; | |
71 | } | |
72 | ||
73 | Double_t massLambda=1.11568; | |
74 | Int_t ncasc=0; | |
75 | ||
76 | // Looking for the cascades... | |
c028b974 | 77 | |
78 | for (i=0; i<nV0; i++) { //loop on V0s | |
79 | ||
c7bafca9 | 80 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); |
81 | v->ChangeMassHypothesis(kLambda0); // the v0 must be Lambda | |
82 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
c028b974 | 83 | |
84 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
c7bafca9 | 85 | Int_t bidx=trk[j]; |
c028b974 | 86 | if (bidx==v->GetNindex()) continue; //bachelor and v0's negative tracks must be different |
c7bafca9 | 87 | AliESDtrack *btrk=event->GetTrack(bidx); |
c7bafca9 | 88 | if (btrk->GetSign()>0) continue; // bachelor's charge |
89 | ||
c028b974 | 90 | AliESDv0 v0(*v), *pv0=&v0; |
c7bafca9 | 91 | AliExternalTrackParam bt(*btrk), *pbt=&bt; |
92 | ||
93 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
94 | if (dca > fDCAmax) continue; | |
95 | ||
c028b974 | 96 | AliESDcascade cascade(*pv0,*pbt,bidx);//constucts a cascade candidate |
97 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
c7bafca9 | 98 | |
99 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
100 | Double_t r2=x*x + y*y; | |
101 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
102 | if (r2 < fRmin*fRmin) continue; | |
103 | ||
c028b974 | 104 | Double_t pxV0,pyV0,pzV0; |
105 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
106 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
107 | ||
c7bafca9 | 108 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); |
109 | if (r2 > (x1*x1+y1*y1)) continue; | |
c7bafca9 | 110 | |
c028b974 | 111 | if (cascade.GetCascadeCosineOfPointingAngle(fX,fY,fZ) <fCPAmax) continue; //condition on the cascade pointing angle |
112 | ||
113 | event->AddCascade(&cascade); | |
c7bafca9 | 114 | ncasc++; |
c028b974 | 115 | } // end loop tracks |
116 | } // end loop V0s | |
c7bafca9 | 117 | |
118 | // Looking for the anti-cascades... | |
c028b974 | 119 | |
120 | for (i=0; i<nV0; i++) { //loop on V0s | |
c7bafca9 | 121 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); |
122 | v->ChangeMassHypothesis(kLambda0Bar); //the v0 must be anti-Lambda | |
123 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
c028b974 | 124 | |
125 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
c7bafca9 | 126 | Int_t bidx=trk[j]; |
c028b974 | 127 | if (bidx==v->GetPindex()) continue; //bachelor and v0's positive tracks must be different |
c7bafca9 | 128 | AliESDtrack *btrk=event->GetTrack(bidx); |
c7bafca9 | 129 | if (btrk->GetSign()<0) continue; // bachelor's charge |
130 | ||
131 | AliESDv0 v0(*v), *pv0=&v0; | |
132 | AliESDtrack bt(*btrk), *pbt=&bt; | |
133 | ||
134 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
135 | if (dca > fDCAmax) continue; | |
136 | ||
c028b974 | 137 | AliESDcascade cascade(*pv0,*pbt,bidx); //constucts a cascade candidate |
138 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
c7bafca9 | 139 | |
140 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
141 | Double_t r2=x*x + y*y; | |
142 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
143 | if (r2 < fRmin*fRmin) continue; | |
144 | ||
c028b974 | 145 | Double_t pxV0,pyV0,pzV0; |
146 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
147 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
148 | ||
c7bafca9 | 149 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); |
150 | if (r2 > (x1*x1+y1*y1)) continue; | |
151 | if (z*z > z1*z1) continue; | |
c7bafca9 | 152 | |
c028b974 | 153 | if (cascade.GetCascadeCosineOfPointingAngle(fX,fY,fZ) < fCPAmax) continue; //condition on the cascade pointing angle |
154 | event->AddCascade(&cascade); | |
c7bafca9 | 155 | ncasc++; |
156 | ||
c028b974 | 157 | } // end loop tracks |
158 | } // end loop V0s | |
c7bafca9 | 159 | |
160 | Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc); | |
161 | ||
162 | return 0; | |
163 | } | |
164 | ||
165 | ||
df53c9d5 | 166 | Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ |
c7bafca9 | 167 | // determinant 2x2 |
168 | return a00*a11 - a01*a10; | |
169 | } | |
170 | ||
df53c9d5 | 171 | Double_t det (Double_t a00,Double_t a01,Double_t a02, |
c7bafca9 | 172 | Double_t a10,Double_t a11,Double_t a12, |
173 | Double_t a20,Double_t a21,Double_t a22) { | |
174 | // determinant 3x3 | |
175 | return | |
176 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
177 | } | |
178 | ||
179 | ||
180 | ||
181 | ||
182 | Double_t AliCascadeVertexer:: | |
183 | PropagateToDCA(AliESDv0 *v, AliExternalTrackParam *t, Double_t b) { | |
184 | //-------------------------------------------------------------------- | |
185 | // This function returns the DCA between the V0 and the track | |
186 | //-------------------------------------------------------------------- | |
187 | Double_t alpha=t->GetAlpha(), cs1=TMath::Cos(alpha), sn1=TMath::Sin(alpha); | |
188 | Double_t r[3]; t->GetXYZ(r); | |
189 | Double_t x1=r[0], y1=r[1], z1=r[2]; | |
190 | Double_t p[3]; t->GetPxPyPz(p); | |
191 | Double_t px1=p[0], py1=p[1], pz1=p[2]; | |
192 | ||
193 | Double_t x2,y2,z2; // position and momentum of V0 | |
194 | Double_t px2,py2,pz2; | |
195 | ||
196 | v->GetXYZ(x2,y2,z2); | |
197 | v->GetPxPyPz(px2,py2,pz2); | |
198 | ||
199 | // calculation dca | |
200 | ||
201 | Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2); | |
202 | Double_t ax= det(py1,pz1,py2,pz2); | |
203 | Double_t ay=-det(px1,pz1,px2,pz2); | |
204 | Double_t az= det(px1,py1,px2,py2); | |
205 | ||
206 | Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az); | |
207 | ||
208 | //points of the DCA | |
209 | Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/ | |
210 | det(px1,py1,pz1,px2,py2,pz2,ax,ay,az); | |
211 | ||
212 | x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1; | |
213 | ||
214 | ||
215 | //propagate track to the points of DCA | |
216 | ||
217 | x1=x1*cs1 + y1*sn1; | |
218 | if (!t->PropagateTo(x1,b)) { | |
219 | Error("PropagateToDCA","Propagation failed !"); | |
220 | return 1.e+33; | |
221 | } | |
222 | ||
223 | return dca; | |
224 | } | |
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