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a9a2d814 | 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 vertex class | |
18 | // | |
19 | // Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr | |
20 | //------------------------------------------------------------------------- | |
a9a2d814 | 21 | #include <TMath.h> |
22 | ||
23 | #include "AliCascadeVertex.h" | |
a9a2d814 | 24 | #include "AliITStrackV2.h" |
116cbefd | 25 | #include "AliV0vertex.h" |
a9a2d814 | 26 | |
27 | ClassImp(AliCascadeVertex) | |
28 | ||
a9a2d814 | 29 | |
30 | inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
31 | // determinant 2x2 | |
32 | return a00*a11 - a01*a10; | |
33 | } | |
34 | ||
35 | inline Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
36 | Double_t a10,Double_t a11,Double_t a12, | |
37 | Double_t a20,Double_t a21,Double_t a22) { | |
38 | // determinant 3x3 | |
39 | return | |
40 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
41 | } | |
42 | ||
43 | ||
a9a2d814 | 44 | AliCascadeVertex::AliCascadeVertex(const AliV0vertex &v,const AliITStrackV2 &t) { |
45 | //-------------------------------------------------------------------- | |
46 | // Main constructor | |
47 | //-------------------------------------------------------------------- | |
48 | fPdgCode=kXiMinus; | |
49 | ||
e23730c7 | 50 | fV0idx[0]=v.GetNindex(); fV0idx[1]=v.GetPindex(); |
51 | fBachIdx=t.GetLabel(); | |
a9a2d814 | 52 | |
53 | //Trivial estimation of the vertex parameters | |
54 | Double_t pt, phi, x, par[5]; | |
55 | Double_t alpha, cs, sn; | |
56 | ||
57 | t.GetExternalParameters(x,par); alpha=t.GetAlpha(); | |
58 | pt=1./TMath::Abs(par[4]); | |
59 | phi=TMath::ASin(par[2]) + alpha; | |
60 | ||
61 | // momentum of the bachelor track | |
62 | ||
63 | Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3]; | |
64 | ||
65 | cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); | |
66 | ||
67 | Double_t x1=x*cs - par[0]*sn; // position of the bachelor at dca (bachelor,V0) | |
68 | Double_t y1=x*sn + par[0]*cs; | |
69 | Double_t z1=par[1]; | |
70 | ||
71 | Double_t x2,y2,z2; // position of the V0 | |
72 | v.GetXYZ(x2,y2,z2); | |
73 | ||
74 | Double_t px2,py2,pz2; // momentum of V0 | |
75 | v.GetPxPyPz(px2,py2,pz2); | |
76 | ||
77 | Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2); | |
78 | ||
79 | Double_t xm=x2+a2*px2; | |
80 | Double_t ym=y2+a2*py2; | |
81 | Double_t zm=z2+a2*pz2; | |
82 | ||
83 | // position of the cascade decay | |
84 | ||
85 | fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm); | |
04b2a5f1 | 86 | |
87 | ||
a9a2d814 | 88 | // invariant mass of the cascade (default is Ximinus) |
89 | ||
90 | Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); | |
91 | Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2); | |
92 | ||
93 | fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- | |
94 | (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); | |
95 | ||
04b2a5f1 | 96 | |
97 | // momenta of the bachelor and the V0 | |
98 | ||
99 | fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1; | |
100 | v.GetNPxPyPz(px2,py2,pz2); | |
101 | fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2; | |
102 | v.GetPPxPyPz(px2,py2,pz2); | |
103 | fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2; | |
104 | ||
105 | ||
a9a2d814 | 106 | fChi2=7.; |
107 | ||
108 | } | |
109 | ||
04b2a5f1 | 110 |