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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 | //------------------------------------------------------------------------- | |
22 | ||
23 | //modified by R. Vernet 30/6/2006 : daughter label | |
24 | //modified by R. Vernet 3/7/2006 : causality | |
25 | //modified by I. Belikov 24/11/2006 : static setter for the default cuts | |
26 | ||
27 | ||
28 | #include <TObjArray.h> | |
29 | #include <TTree.h> | |
30 | ||
31 | #include "AliESD.h" | |
32 | #include "AliESDv0.h" | |
33 | #include "AliESDcascade.h" | |
34 | #include "AliCascadeVertexer.h" | |
35 | ||
36 | ClassImp(AliCascadeVertexer) | |
37 | ||
38 | //A set of loose cuts | |
39 | Double_t | |
40 | AliCascadeVertexer::fgChi2max=33.; //maximal allowed chi2 | |
41 | Double_t | |
42 | AliCascadeVertexer::fgDV0min=0.05; //min V0 impact parameter | |
43 | Double_t | |
44 | AliCascadeVertexer::fgMassWin=0.01; //"window" around the Lambda mass | |
45 | Double_t | |
46 | AliCascadeVertexer::fgDBachMin=0.035; //min bachelor impact parameter | |
47 | Double_t | |
48 | AliCascadeVertexer::fgDCAmax=0.10; //max DCA between the V0 and the track | |
49 | Double_t | |
50 | AliCascadeVertexer::fgCPAmax=0.9985; //max cosine of the cascade pointing angle | |
51 | Double_t | |
52 | AliCascadeVertexer::fgRmin=0.2; //min radius of the fiducial volume | |
53 | Double_t | |
54 | AliCascadeVertexer::fgRmax=100.; //max radius of the fiducial volume | |
55 | ||
56 | ||
57 | Int_t AliCascadeVertexer::V0sTracks2CascadeVertices(AliESD *event) { | |
58 | //-------------------------------------------------------------------- | |
59 | // This function reconstructs cascade vertices | |
60 | // Adapted to the ESD by I.Belikov (Jouri.Belikov@cern.ch) | |
61 | //-------------------------------------------------------------------- | |
62 | const AliESDVertex *vtx=event->GetVertex(); | |
63 | Double_t xv=vtx->GetXv(), yv=vtx->GetYv(), zv=vtx->GetZv(); | |
64 | ||
65 | Double_t b=event->GetMagneticField(); | |
66 | Int_t nV0=(Int_t)event->GetNumberOfV0s(); | |
67 | ||
68 | //stores relevant V0s in an array | |
69 | TObjArray vtcs(nV0); | |
70 | Int_t i; | |
71 | for (i=0; i<nV0; i++) { | |
72 | AliESDv0 *v=event->GetV0(i); | |
73 | if (v->GetOnFlyStatus()) continue; | |
74 | if (v->GetD(xv,yv,zv)<fDV0min) continue; | |
75 | vtcs.AddLast(v); | |
76 | } | |
77 | nV0=vtcs.GetEntriesFast(); | |
78 | ||
79 | // stores relevant tracks in another array | |
80 | Int_t nentr=(Int_t)event->GetNumberOfTracks(); | |
81 | TArrayI trk(nentr); Int_t ntr=0; | |
82 | for (i=0; i<nentr; i++) { | |
83 | AliESDtrack *esdtr=event->GetTrack(i); | |
84 | UInt_t status=esdtr->GetStatus(); | |
85 | UInt_t flags=AliESDtrack::kITSin|AliESDtrack::kTPCin| | |
86 | AliESDtrack::kTPCpid|AliESDtrack::kESDpid; | |
87 | ||
88 | if ((status&AliESDtrack::kITSrefit)==0) | |
89 | if (flags!=status) continue; | |
90 | ||
91 | if (TMath::Abs(esdtr->GetD(xv,yv,b))<fDBachMin) continue; | |
92 | ||
93 | trk[ntr++]=i; | |
94 | } | |
95 | ||
96 | Double_t massLambda=1.11568; | |
97 | Int_t ncasc=0; | |
98 | ||
99 | // Looking for the cascades... | |
100 | ||
101 | for (i=0; i<nV0; i++) { //loop on V0s | |
102 | ||
103 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
104 | v->ChangeMassHypothesis(kLambda0); // the v0 must be Lambda | |
105 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
106 | ||
107 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
108 | Int_t bidx=trk[j]; | |
109 | //Bo: if (bidx==v->GetNindex()) continue; //bachelor and v0's negative tracks must be different | |
110 | if (bidx==v->GetIndex(0)) continue; //Bo: consistency 0 for neg | |
111 | AliESDtrack *btrk=event->GetTrack(bidx); | |
112 | if (btrk->GetSign()>0) continue; // bachelor's charge | |
113 | ||
114 | AliESDv0 v0(*v), *pv0=&v0; | |
115 | AliExternalTrackParam bt(*btrk), *pbt=&bt; | |
116 | ||
117 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
118 | if (dca > fDCAmax) continue; | |
119 | ||
120 | AliESDcascade cascade(*pv0,*pbt,bidx);//constucts a cascade candidate | |
121 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
122 | ||
123 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
124 | Double_t r2=x*x + y*y; | |
125 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
126 | if (r2 < fRmin*fRmin) continue; | |
127 | ||
128 | Double_t pxV0,pyV0,pzV0; | |
129 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
130 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
131 | ||
132 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
133 | if (r2 > (x1*x1+y1*y1)) continue; | |
134 | ||
135 | if (cascade.GetCascadeCosineOfPointingAngle(xv,yv,zv) <fCPAmax) continue; //condition on the cascade pointing angle | |
136 | ||
137 | event->AddCascade(&cascade); | |
138 | ncasc++; | |
139 | } // end loop tracks | |
140 | } // end loop V0s | |
141 | ||
142 | // Looking for the anti-cascades... | |
143 | ||
144 | for (i=0; i<nV0; i++) { //loop on V0s | |
145 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
146 | v->ChangeMassHypothesis(kLambda0Bar); //the v0 must be anti-Lambda | |
147 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
148 | ||
149 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
150 | Int_t bidx=trk[j]; | |
151 | //Bo: if (bidx==v->GetPindex()) continue; //bachelor and v0's positive tracks must be different | |
152 | if (bidx==v->GetIndex(1)) continue; //Bo: consistency 1 for pos | |
153 | AliESDtrack *btrk=event->GetTrack(bidx); | |
154 | if (btrk->GetSign()<0) continue; // bachelor's charge | |
155 | ||
156 | AliESDv0 v0(*v), *pv0=&v0; | |
157 | AliESDtrack bt(*btrk), *pbt=&bt; | |
158 | ||
159 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
160 | if (dca > fDCAmax) continue; | |
161 | ||
162 | AliESDcascade cascade(*pv0,*pbt,bidx); //constucts a cascade candidate | |
163 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
164 | ||
165 | Double_t x,y,z; cascade.GetXYZ(x,y,z); | |
166 | Double_t r2=x*x + y*y; | |
167 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
168 | if (r2 < fRmin*fRmin) continue; | |
169 | ||
170 | Double_t pxV0,pyV0,pzV0; | |
171 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
172 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
173 | ||
174 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
175 | if (r2 > (x1*x1+y1*y1)) continue; | |
176 | if (z*z > z1*z1) continue; | |
177 | ||
178 | if (cascade.GetCascadeCosineOfPointingAngle(xv,yv,zv) < fCPAmax) continue; //condition on the cascade pointing angle | |
179 | event->AddCascade(&cascade); | |
180 | ncasc++; | |
181 | ||
182 | } // end loop tracks | |
183 | } // end loop V0s | |
184 | ||
185 | Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc); | |
186 | ||
187 | return 0; | |
188 | } | |
189 | ||
190 | ||
191 | Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
192 | // determinant 2x2 | |
193 | return a00*a11 - a01*a10; | |
194 | } | |
195 | ||
196 | Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
197 | Double_t a10,Double_t a11,Double_t a12, | |
198 | Double_t a20,Double_t a21,Double_t a22) { | |
199 | // determinant 3x3 | |
200 | return | |
201 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
202 | } | |
203 | ||
204 | ||
205 | ||
206 | ||
207 | Double_t AliCascadeVertexer:: | |
208 | PropagateToDCA(AliESDv0 *v, AliExternalTrackParam *t, Double_t b) { | |
209 | //-------------------------------------------------------------------- | |
210 | // This function returns the DCA between the V0 and the track | |
211 | //-------------------------------------------------------------------- | |
212 | Double_t alpha=t->GetAlpha(), cs1=TMath::Cos(alpha), sn1=TMath::Sin(alpha); | |
213 | Double_t r[3]; t->GetXYZ(r); | |
214 | Double_t x1=r[0], y1=r[1], z1=r[2]; | |
215 | Double_t p[3]; t->GetPxPyPz(p); | |
216 | Double_t px1=p[0], py1=p[1], pz1=p[2]; | |
217 | ||
218 | Double_t x2,y2,z2; // position and momentum of V0 | |
219 | Double_t px2,py2,pz2; | |
220 | ||
221 | v->GetXYZ(x2,y2,z2); | |
222 | v->GetPxPyPz(px2,py2,pz2); | |
223 | ||
224 | // calculation dca | |
225 | ||
226 | Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2); | |
227 | Double_t ax= det(py1,pz1,py2,pz2); | |
228 | Double_t ay=-det(px1,pz1,px2,pz2); | |
229 | Double_t az= det(px1,py1,px2,py2); | |
230 | ||
231 | Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az); | |
232 | ||
233 | //points of the DCA | |
234 | Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/ | |
235 | det(px1,py1,pz1,px2,py2,pz2,ax,ay,az); | |
236 | ||
237 | x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1; | |
238 | ||
239 | ||
240 | //propagate track to the points of DCA | |
241 | ||
242 | x1=x1*cs1 + y1*sn1; | |
243 | if (!t->PropagateTo(x1,b)) { | |
244 | Error("PropagateToDCA","Propagation failed !"); | |
245 | return 1.e+33; | |
246 | } | |
247 | ||
248 | return dca; | |
249 | } | |
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