1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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8 * documentation strictly for non-commercial purposes is hereby granted *
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14 **************************************************************************/
16 //-------------------------------------------------------------------------
18 // Implementation of the V0 vertex class
19 // Numerical part - AliHelix functionality used
21 // Origin: Marian Ivanov marian.ivanov@cern.ch
22 //-------------------------------------------------------------------------
31 void AliV0::Update(Float_t vertex[3])
36 // Float_t distance1,distance2;
39 AliHelix phelix(fParamP);
40 AliHelix mhelix(fParamN);
42 //find intersection linear
44 Double_t phase[2][2],radius[2];
45 Int_t points = phelix.GetRPHIintersections(mhelix, phase, radius,200);
46 Double_t delta1=10000,delta2=10000;
48 if (points<=0) return;
50 phelix.LinearDCA(mhelix,phase[0][0],phase[0][1],radius[0],delta1);
51 phelix.LinearDCA(mhelix,phase[0][0],phase[0][1],radius[0],delta1);
52 phelix.LinearDCA(mhelix,phase[0][0],phase[0][1],radius[0],delta1);
55 phelix.LinearDCA(mhelix,phase[1][0],phase[1][1],radius[1],delta2);
56 phelix.LinearDCA(mhelix,phase[1][0],phase[1][1],radius[1],delta2);
57 phelix.LinearDCA(mhelix,phase[1][0],phase[1][1],radius[1],delta2);
59 distance1 = TMath::Min(delta1,delta2);
62 //find intersection parabolic
64 points = phelix.GetRPHIintersections(mhelix, phase, radius);
65 delta1=10000,delta2=10000;
66 Double_t d1=1000.,d2=10000.;
67 Double_t err[3],angles[3];
68 if (points<=0) return;
70 phelix.ParabolicDCA(mhelix,phase[0][0],phase[0][1],radius[0],delta1);
71 phelix.ParabolicDCA(mhelix,phase[0][0],phase[0][1],radius[0],delta1);
72 if (TMath::Abs(fParamP.GetX()-TMath::Sqrt(radius[0])<3) && TMath::Abs(fParamN.GetX()-TMath::Sqrt(radius[0])<3)){
73 // if we are close to vertex use error parama
75 err[1] = fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]+0.05*0.05
76 +0.3*(fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]);
77 err[2] = fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]+0.05*0.05
78 +0.3*(fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]);
80 phelix.GetAngle(phase[0][0],mhelix,phase[0][1],angles);
81 Double_t tfi = TMath::Abs(TMath::Tan(angles[0]));
82 Double_t tlam = TMath::Abs(TMath::Tan(angles[1]));
83 err[0] = err[1]/((0.2+tfi)*(0.2+tfi))+err[2]/((0.2+tlam)*(0.2+tlam));
84 err[0] = ((err[1]*err[2]/((0.2+tfi)*(0.2+tfi)*(0.2+tlam)*(0.2+tlam))))/err[0];
85 phelix.ParabolicDCA2(mhelix,phase[0][0],phase[0][1],radius[0],delta1,err);
88 phelix.Evaluate(phase[0][0],xd);
89 mhelix.Evaluate(phase[0][1],xm);
90 d1 = (xd[0]-xm[0])*(xd[0]-xm[0])+(xd[1]-xm[1])*(xd[1]-xm[1])+(xd[2]-xm[2])*(xd[2]-xm[2]);
93 phelix.ParabolicDCA(mhelix,phase[1][0],phase[1][1],radius[1],delta2);
94 phelix.ParabolicDCA(mhelix,phase[1][0],phase[1][1],radius[1],delta2);
95 if (TMath::Abs(fParamP.GetX()-TMath::Sqrt(radius[1])<3) && TMath::Abs(fParamN.GetX()-TMath::Sqrt(radius[1])<3)){
96 // if we are close to vertex use error paramatrization
98 err[1] = fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]+0.05*0.05
99 +0.3*(fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]);
100 err[2] = fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]+0.05*0.05
101 +0.3*(fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]);
103 phelix.GetAngle(phase[1][0],mhelix,phase[1][1],angles);
104 Double_t tfi = TMath::Abs(TMath::Tan(angles[0]));
105 Double_t tlam = TMath::Abs(TMath::Tan(angles[1]));
106 err[0] = err[1]/((0.2+tfi)*(0.2+tfi))+err[2]/((0.2+tlam)*(0.2+tlam));
107 err[0] = ((err[1]*err[2]/((0.2+tfi)*(0.2+tfi)*(0.2+tlam)*(0.2+tlam))))/err[0];
108 phelix.ParabolicDCA2(mhelix,phase[1][0],phase[1][1],radius[1],delta2,err);
110 Double_t xd[3],xm[3];
111 phelix.Evaluate(phase[1][0],xd);
112 mhelix.Evaluate(phase[1][1],xm);
113 d2 = (xd[0]-xm[0])*(xd[0]-xm[0])+(xd[1]-xm[1])*(xd[1]-xm[1])+(xd[2]-xm[2])*(xd[2]-xm[2]);
116 distance2 = TMath::Min(delta1,delta2);
119 Double_t xd[3],xm[3];
120 phelix.Evaluate(phase[0][0],xd);
121 mhelix.Evaluate(phase[0][1], xm);
122 fXr[0] = 0.5*(xd[0]+xm[0]);
123 fXr[1] = 0.5*(xd[1]+xm[1]);
124 fXr[2] = 0.5*(xd[2]+xm[2]);
126 Float_t wy = fParamP.GetCovariance()[0]/(fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]);
127 Float_t wz = fParamP.GetCovariance()[2]/(fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]);
128 fXr[0] = 0.5*( (1.-wy)*xd[0]+ wy*xm[0] + (1.-wz)*xd[0]+ wz*xm[0] );
129 fXr[1] = (1.-wy)*xd[1]+ wy*xm[1];
130 fXr[2] = (1.-wz)*xd[2]+ wz*xm[2];
132 phelix.GetMomentum(phase[0][0],fPP);
133 mhelix.GetMomentum(phase[0][1],fPM);
134 phelix.GetAngle(phase[0][0],mhelix,phase[0][1],fAngle);
135 fRr = TMath::Sqrt(fXr[0]*fXr[0]+fXr[1]*fXr[1]);
138 Double_t xd[3],xm[3];
139 phelix.Evaluate(phase[1][0],xd);
140 mhelix.Evaluate(phase[1][1], xm);
141 fXr[0] = 0.5*(xd[0]+xm[0]);
142 fXr[1] = 0.5*(xd[1]+xm[1]);
143 fXr[2] = 0.5*(xd[2]+xm[2]);
144 Float_t wy = fParamP.GetCovariance()[0]/(fParamP.GetCovariance()[0]+fParamN.GetCovariance()[0]);
145 Float_t wz = fParamP.GetCovariance()[2]/(fParamP.GetCovariance()[2]+fParamN.GetCovariance()[2]);
146 fXr[0] = 0.5*( (1.-wy)*xd[0]+ wy*xm[0] + (1.-wz)*xd[0]+ wz*xm[0] );
147 fXr[1] = (1.-wy)*xd[1]+ wy*xm[1];
148 fXr[2] = (1.-wz)*xd[2]+ wz*xm[2];
150 phelix.GetMomentum(phase[1][0], fPP);
151 mhelix.GetMomentum(phase[1][1], fPM);
152 phelix.GetAngle(phase[1][0],mhelix,phase[1][1],fAngle);
153 fRr = TMath::Sqrt(fXr[0]*fXr[0]+fXr[1]*fXr[1]);
155 fDist1 = TMath::Sqrt(TMath::Min(d1,d2));
156 fDist2 = TMath::Sqrt(distance2);
159 Double_t v[3] = {fXr[0]-vertex[0],fXr[1]-vertex[1],fXr[2]-vertex[2]};
160 Double_t p[3] = {fPP[0]+fPM[0], fPP[1]+fPM[1],fPP[2]+fPM[2]};
161 Double_t vnorm2 = v[0]*v[0]+v[1]*v[1];
162 if (TMath::Abs(v[2])>100000) return;
163 Double_t vnorm3 = TMath::Sqrt(TMath::Abs(v[2]*v[2]+vnorm2));
164 vnorm2 = TMath::Sqrt(vnorm2);
165 Double_t pnorm2 = p[0]*p[0]+p[1]*p[1];
166 Double_t pnorm3 = TMath::Sqrt(p[2]*p[2]+pnorm2);
167 pnorm2 = TMath::Sqrt(pnorm2);
168 fPointAngleFi = (v[0]*p[0]+v[1]*p[1])/(vnorm2*pnorm2);
169 fPointAngleTh = (v[2]*p[2]+vnorm2*pnorm2)/(vnorm3*pnorm3);
170 fPointAngle = (v[0]*p[0]+v[1]*p[1]+v[2]*p[2])/(vnorm3*pnorm3);