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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 | #include "AliESDEvent.h" | |
28 | #include "AliESDcascade.h" | |
29 | #include "AliCascadeVertexer.h" | |
30 | ||
31 | ClassImp(AliCascadeVertexer) | |
32 | ||
33 | //A set of loose cuts | |
34 | Double_t | |
35 | AliCascadeVertexer::fgChi2max=33.; //maximal allowed chi2 | |
36 | Double_t | |
37 | AliCascadeVertexer::fgDV0min=0.05; //min V0 impact parameter | |
38 | Double_t | |
39 | AliCascadeVertexer::fgMassWin=0.01; //"window" around the Lambda mass | |
40 | Double_t | |
41 | AliCascadeVertexer::fgDBachMin=0.035; //min bachelor impact parameter | |
42 | Double_t | |
43 | AliCascadeVertexer::fgDCAmax=0.10; //max DCA between the V0 and the track | |
44 | Double_t | |
45 | AliCascadeVertexer::fgCPAmin=0.9985; //min cosine of the cascade pointing angle | |
46 | Double_t | |
47 | AliCascadeVertexer::fgRmin=0.2; //min radius of the fiducial volume | |
48 | Double_t | |
49 | AliCascadeVertexer::fgRmax=100.; //max radius of the fiducial volume | |
50 | ||
51 | ||
52 | Int_t AliCascadeVertexer::V0sTracks2CascadeVertices(AliESDEvent *event) { | |
53 | //-------------------------------------------------------------------- | |
54 | // This function reconstructs cascade vertices | |
55 | // Adapted to the ESD by I.Belikov (Jouri.Belikov@cern.ch) | |
56 | //-------------------------------------------------------------------- | |
57 | const AliESDVertex *vtxT3D=event->GetPrimaryVertex(); | |
58 | ||
59 | Double_t xPrimaryVertex=vtxT3D->GetXv(); | |
60 | Double_t yPrimaryVertex=vtxT3D->GetYv(); | |
61 | Double_t zPrimaryVertex=vtxT3D->GetZv(); | |
62 | ||
63 | Double_t b=event->GetMagneticField(); | |
64 | Int_t nV0=(Int_t)event->GetNumberOfV0s(); | |
65 | ||
66 | //stores relevant V0s in an array | |
67 | TObjArray vtcs(nV0); | |
68 | Int_t i; | |
69 | for (i=0; i<nV0; i++) { | |
70 | AliESDv0 *v=event->GetV0(i); | |
71 | if (v->GetOnFlyStatus()) continue; | |
72 | if (v->GetD(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex)<fDV0min) continue; | |
73 | vtcs.AddLast(v); | |
74 | } | |
75 | nV0=vtcs.GetEntriesFast(); | |
76 | ||
77 | // stores relevant tracks in another array | |
78 | Int_t nentr=(Int_t)event->GetNumberOfTracks(); | |
79 | TArrayI trk(nentr); Int_t ntr=0; | |
80 | for (i=0; i<nentr; i++) { | |
81 | AliESDtrack *esdtr=event->GetTrack(i); | |
82 | ULong_t status=esdtr->GetStatus(); | |
83 | ||
84 | if ((status&AliESDtrack::kITSrefit)==0) | |
85 | if ((status&AliESDtrack::kTPCrefit)==0) continue; | |
86 | ||
87 | if (TMath::Abs(esdtr->GetD(xPrimaryVertex,yPrimaryVertex,b))<fDBachMin) continue; | |
88 | ||
89 | trk[ntr++]=i; | |
90 | } | |
91 | ||
92 | Double_t massLambda=1.11568; | |
93 | Int_t ncasc=0; | |
94 | ||
95 | // Looking for the cascades... | |
96 | ||
97 | for (i=0; i<nV0; i++) { //loop on V0s | |
98 | ||
99 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
100 | v->ChangeMassHypothesis(kLambda0); // the v0 must be Lambda | |
101 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
102 | ||
103 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
104 | Int_t bidx=trk[j]; | |
105 | //Bo: if (bidx==v->GetNindex()) continue; //bachelor and v0's negative tracks must be different | |
106 | if (bidx==v->GetIndex(0)) continue; //Bo: consistency 0 for neg | |
107 | AliESDtrack *btrk=event->GetTrack(bidx); | |
108 | if (btrk->GetSign()>0) continue; // bachelor's charge | |
109 | ||
110 | AliESDv0 v0(*v), *pv0=&v0; | |
111 | AliExternalTrackParam bt(*btrk), *pbt=&bt; | |
112 | ||
113 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
114 | if (dca > fDCAmax) continue; | |
115 | ||
116 | AliESDcascade cascade(*pv0,*pbt,bidx);//constucts a cascade candidate | |
117 | //PH if (cascade.GetChi2Xi() > fChi2max) continue; | |
118 | ||
119 | Double_t x,y,z; cascade.GetXYZcascade(x,y,z); // Bo: bug correction | |
120 | Double_t r2=x*x + y*y; | |
121 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
122 | if (r2 < fRmin*fRmin) continue; | |
123 | ||
124 | Double_t pxV0,pyV0,pzV0; | |
125 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
126 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
127 | ||
128 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
129 | if (r2 > (x1*x1+y1*y1)) continue; | |
130 | ||
131 | if (cascade.GetCascadeCosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex) <fCPAmin) continue; //condition on the cascade pointing angle | |
132 | ||
133 | cascade.SetDcaXiDaughters(dca); | |
134 | event->AddCascade(&cascade); | |
135 | ncasc++; | |
136 | } // end loop tracks | |
137 | } // end loop V0s | |
138 | ||
139 | // Looking for the anti-cascades... | |
140 | ||
141 | for (i=0; i<nV0; i++) { //loop on V0s | |
142 | AliESDv0 *v=(AliESDv0*)vtcs.UncheckedAt(i); | |
143 | v->ChangeMassHypothesis(kLambda0Bar); //the v0 must be anti-Lambda | |
144 | if (TMath::Abs(v->GetEffMass()-massLambda)>fMassWin) continue; | |
145 | ||
146 | for (Int_t j=0; j<ntr; j++) {//loop on tracks | |
147 | Int_t bidx=trk[j]; | |
148 | //Bo: if (bidx==v->GetPindex()) continue; //bachelor and v0's positive tracks must be different | |
149 | if (bidx==v->GetIndex(1)) continue; //Bo: consistency 1 for pos | |
150 | AliESDtrack *btrk=event->GetTrack(bidx); | |
151 | if (btrk->GetSign()<0) continue; // bachelor's charge | |
152 | ||
153 | AliESDv0 v0(*v), *pv0=&v0; | |
154 | AliESDtrack bt(*btrk), *pbt=&bt; | |
155 | ||
156 | Double_t dca=PropagateToDCA(pv0,pbt,b); | |
157 | if (dca > fDCAmax) continue; | |
158 | ||
159 | AliESDcascade cascade(*pv0,*pbt,bidx); //constucts a cascade candidate | |
160 | //PH if (cascade.GetChi2Xi() > fChi2max) continue; | |
161 | ||
162 | Double_t x,y,z; cascade.GetXYZcascade(x,y,z); // Bo: bug correction | |
163 | Double_t r2=x*x + y*y; | |
164 | if (r2 > fRmax*fRmax) continue; // condition on fiducial zone | |
165 | if (r2 < fRmin*fRmin) continue; | |
166 | ||
167 | Double_t pxV0,pyV0,pzV0; | |
168 | pv0->GetPxPyPz(pxV0,pyV0,pzV0); | |
169 | if (x*pxV0+y*pyV0+z*pzV0 < 0) continue; //causality | |
170 | ||
171 | Double_t x1,y1,z1; pv0->GetXYZ(x1,y1,z1); | |
172 | if (r2 > (x1*x1+y1*y1)) continue; | |
173 | ||
174 | if (cascade.GetCascadeCosineOfPointingAngle(xPrimaryVertex,yPrimaryVertex,zPrimaryVertex) < fCPAmin) continue; //condition on the cascade pointing angle | |
175 | ||
176 | cascade.SetDcaXiDaughters(dca); | |
177 | event->AddCascade(&cascade); | |
178 | ncasc++; | |
179 | ||
180 | } // end loop tracks | |
181 | } // end loop V0s | |
182 | ||
183 | Info("V0sTracks2CascadeVertices","Number of reconstructed cascades: %d",ncasc); | |
184 | ||
185 | return 0; | |
186 | } | |
187 | ||
188 | ||
189 | Double_t AliCascadeVertexer::Det(Double_t a00, Double_t a01, Double_t a10, Double_t a11) const { | |
190 | //-------------------------------------------------------------------- | |
191 | // This function calculates locally a 2x2 determinant | |
192 | //-------------------------------------------------------------------- | |
193 | return a00*a11 - a01*a10; | |
194 | } | |
195 | ||
196 | Double_t AliCascadeVertexer::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) const { | |
199 | //-------------------------------------------------------------------- | |
200 | // This function calculates locally a 3x3 determinant | |
201 | //-------------------------------------------------------------------- | |
202 | return a00*Det(a11,a12,a21,a22)-a01*Det(a10,a12,a20,a22)+a02*Det(a10,a11,a20,a21); | |
203 | } | |
204 | ||
205 | ||
206 | ||
207 | ||
208 | Double_t AliCascadeVertexer::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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