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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 "AliESDEvent.h" | |
32 | #include "AliESDv0.h" | |
33 | #include "AliESDcascade.h" | |
34 | #include "AliCascadeVertexer.h" | |
35 | #include "AliESDtrack.h" | |
36 | #include "AliESDVertex.h" | |
37 | ||
38 | ClassImp(AliCascadeVertexer) | |
39 | ||
40 | //A set of loose cuts | |
41 | Double_t | |
42 | AliCascadeVertexer::fgChi2max=33.; //maximal allowed chi2 | |
43 | Double_t | |
44 | AliCascadeVertexer::fgDV0min=0.05; //min V0 impact parameter | |
45 | Double_t | |
46 | AliCascadeVertexer::fgMassWin=0.01; //"window" around the Lambda mass | |
47 | Double_t | |
48 | AliCascadeVertexer::fgDBachMin=0.035; //min bachelor impact parameter | |
49 | Double_t | |
50 | AliCascadeVertexer::fgDCAmax=0.10; //max DCA between the V0 and the track | |
51 | Double_t | |
52 | AliCascadeVertexer::fgCPAmin=0.9985; //min cosine of the cascade pointing angle | |
53 | Double_t | |
54 | AliCascadeVertexer::fgRmin=0.2; //min radius of the fiducial volume | |
55 | Double_t | |
56 | AliCascadeVertexer::fgRmax=100.; //max radius of the fiducial volume | |
57 | ||
58 | ||
59 | Int_t AliCascadeVertexer::V0sTracks2CascadeVertices(AliESDEvent *event) { | |
60 | //-------------------------------------------------------------------- | |
61 | // This function reconstructs cascade vertices | |
62 | // Adapted to the ESD by I.Belikov (Jouri.Belikov@cern.ch) | |
63 | //-------------------------------------------------------------------- | |
64 | const AliESDVertex *vtxSPD=event->GetVertex(); | |
65 | const AliESDVertex *vtxT3D=event->GetPrimaryVertex(); | |
66 | ||
67 | Double_t xPrimaryVertex=999, yPrimaryVertex=999, zPrimaryVertex=999; | |
68 | if (vtxT3D->GetStatus()) { | |
69 | xPrimaryVertex=vtxT3D->GetXv(); | |
70 | yPrimaryVertex=vtxT3D->GetYv(); | |
71 | zPrimaryVertex=vtxT3D->GetZv(); | |
72 | } | |
73 | else { | |
74 | xPrimaryVertex=vtxSPD->GetXv(); | |
75 | yPrimaryVertex=vtxSPD->GetYv(); | |
76 | zPrimaryVertex=vtxSPD->GetZv(); | |
77 | } | |
78 | ||
79 | Double_t b=event->GetMagneticField(); | |
80 | Int_t nV0=(Int_t)event->GetNumberOfV0s(); | |
81 | ||
82 | //stores relevant V0s in an array | |
83 | TObjArray vtcs(nV0); | |
84 | Int_t i; | |
85 | for (i=0; i<nV0; i++) { | |
86 | AliESDv0 *v=event->GetV0(i); | |
87 | if (v->GetOnFlyStatus()) continue; | |
88 | if (v->GetD(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex)<fDV0min) continue; | |
89 | vtcs.AddLast(v); | |
90 | } | |
91 | nV0=vtcs.GetEntriesFast(); | |
92 | ||
93 | // stores relevant tracks in another array | |
94 | Int_t nentr=(Int_t)event->GetNumberOfTracks(); | |
95 | TArrayI trk(nentr); Int_t ntr=0; | |
96 | for (i=0; i<nentr; i++) { | |
97 | AliESDtrack *esdtr=event->GetTrack(i); | |
98 | ULong_t status=esdtr->GetStatus(); | |
99 | ||
100 | if ((status&AliESDtrack::kITSrefit)==0) | |
101 | if ((status&AliESDtrack::kTPCrefit)==0) continue; | |
102 | ||
103 | if (TMath::Abs(esdtr->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDBachMin) continue; | |
104 | ||
105 | trk[ntr++]=i; | |
106 | } | |
107 | ||
108 | Double_t massLambda=1.11568; | |
109 | Int_t ncasc=0; | |
110 | ||
111 | // Looking for the cascades... | |
112 | ||
113 | for (i=0; i<nV0; i++) { //loop on V0s | |
114 | ||
115 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
116 | v->ChangeMassHypothesis(kLambda0); // the v0 must be Lambda | |
117 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
118 | ||
119 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
120 | Int_t bidx=trk[j]; | |
121 | //Bo: if (bidx==v->GetNindex()) continue; //bachelor and v0's negative tracks must be different | |
122 | if (bidx==v->GetIndex(0)) continue; //Bo: consistency 0 for neg | |
123 | AliESDtrack *btrk=event->GetTrack(bidx); | |
124 | if (btrk->GetSign()>0) continue; // bachelor's charge | |
125 | ||
126 | AliESDv0 v0(*v), *pv0=&v0; | |
127 | AliExternalTrackParam bt(*btrk), *pbt=&bt; | |
128 | ||
129 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
130 | if (dca > fDCAmax) continue; | |
131 | ||
132 | AliESDcascade cascade(*pv0,*pbt,bidx);//constucts a cascade candidate | |
133 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
134 | ||
135 | Double_t x,y,z; cascade.GetXYZcascade(x,y,z); // Bo: bug correction | |
136 | Double_t r2=x*x + y*y; | |
137 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
138 | if (r2 < fRmin*fRmin) continue; | |
139 | ||
140 | Double_t pxV0,pyV0,pzV0; | |
141 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
142 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
143 | ||
144 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
145 | if (r2 > (x1*x1+y1*y1)) continue; | |
146 | ||
147 | if (cascade.GetCascadeCosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex) <fCPAmin) continue; //condition on the cascade pointing angle | |
148 | ||
149 | event->AddCascade(&cascade); | |
150 | ncasc++; | |
151 | } // end loop tracks | |
152 | } // end loop V0s | |
153 | ||
154 | // Looking for the anti-cascades... | |
155 | ||
156 | for (i=0; i<nV0; i++) { //loop on V0s | |
157 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
158 | v->ChangeMassHypothesis(kLambda0Bar); //the v0 must be anti-Lambda | |
159 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
160 | ||
161 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
162 | Int_t bidx=trk[j]; | |
163 | //Bo: if (bidx==v->GetPindex()) continue; //bachelor and v0's positive tracks must be different | |
164 | if (bidx==v->GetIndex(1)) continue; //Bo: consistency 1 for pos | |
165 | AliESDtrack *btrk=event->GetTrack(bidx); | |
166 | if (btrk->GetSign()<0) continue; // bachelor's charge | |
167 | ||
168 | AliESDv0 v0(*v), *pv0=&v0; | |
169 | AliESDtrack bt(*btrk), *pbt=&bt; | |
170 | ||
171 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
172 | if (dca > fDCAmax) continue; | |
173 | ||
174 | AliESDcascade cascade(*pv0,*pbt,bidx); //constucts a cascade candidate | |
175 | if (cascade.GetChi2Xi() > fChi2max) continue; | |
176 | ||
177 | Double_t x,y,z; cascade.GetXYZcascade(x,y,z); // Bo: bug correction | |
178 | Double_t r2=x*x + y*y; | |
179 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
180 | if (r2 < fRmin*fRmin) continue; | |
181 | ||
182 | Double_t pxV0,pyV0,pzV0; | |
183 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
184 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
185 | ||
186 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
187 | if (r2 > (x1*x1+y1*y1)) continue; | |
188 | if (z*z > z1*z1) continue; | |
189 | ||
190 | if (cascade.GetCascadeCosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex) < fCPAmin) continue; //condition on the cascade pointing angle | |
191 | event->AddCascade(&cascade); | |
192 | ncasc++; | |
193 | ||
194 | } // end loop tracks | |
195 | } // end loop V0s | |
196 | ||
197 | Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc); | |
198 | ||
199 | return 0; | |
200 | } | |
201 | ||
202 | ||
203 | Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
204 | // determinant 2x2 | |
205 | return a00*a11 - a01*a10; | |
206 | } | |
207 | ||
208 | Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
209 | Double_t a10,Double_t a11,Double_t a12, | |
210 | Double_t a20,Double_t a21,Double_t a22) { | |
211 | // determinant 3x3 | |
212 | return | |
213 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
214 | } | |
215 | ||
216 | ||
217 | ||
218 | ||
219 | Double_t AliCascadeVertexer:: | |
220 | PropagateToDCA(AliESDv0 *v, AliExternalTrackParam *t, Double_t b) { | |
221 | //-------------------------------------------------------------------- | |
222 | // This function returns the DCA between the V0 and the track | |
223 | //-------------------------------------------------------------------- | |
224 | Double_t alpha=t->GetAlpha(), cs1=TMath::Cos(alpha), sn1=TMath::Sin(alpha); | |
225 | Double_t r[3]; t->GetXYZ(r); | |
226 | Double_t x1=r[0], y1=r[1], z1=r[2]; | |
227 | Double_t p[3]; t->GetPxPyPz(p); | |
228 | Double_t px1=p[0], py1=p[1], pz1=p[2]; | |
229 | ||
230 | Double_t x2,y2,z2; // position and momentum of V0 | |
231 | Double_t px2,py2,pz2; | |
232 | ||
233 | v->GetXYZ(x2,y2,z2); | |
234 | v->GetPxPyPz(px2,py2,pz2); | |
235 | ||
236 | // calculation dca | |
237 | ||
238 | Double_t dd= det(x2-x1,y2-y1,z2-z1,px1,py1,pz1,px2,py2,pz2); | |
239 | Double_t ax= det(py1,pz1,py2,pz2); | |
240 | Double_t ay=-det(px1,pz1,px2,pz2); | |
241 | Double_t az= det(px1,py1,px2,py2); | |
242 | ||
243 | Double_t dca=TMath::Abs(dd)/TMath::Sqrt(ax*ax + ay*ay + az*az); | |
244 | ||
245 | //points of the DCA | |
246 | Double_t t1 = det(x2-x1,y2-y1,z2-z1,px2,py2,pz2,ax,ay,az)/ | |
247 | det(px1,py1,pz1,px2,py2,pz2,ax,ay,az); | |
248 | ||
249 | x1 += px1*t1; y1 += py1*t1; //z1 += pz1*t1; | |
250 | ||
251 | ||
252 | //propagate track to the points of DCA | |
253 | ||
254 | x1=x1*cs1 + y1*sn1; | |
255 | if (!t->PropagateTo(x1,b)) { | |
256 | Error("PropagateToDCA","Propagation failed !"); | |
257 | return 1.e+33; | |
258 | } | |
259 | ||
260 | return dca; | |
261 | } | |
262 | ||
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