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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 | //------------------------------------------------------------------------- | |
21 | #include <iostream.h> | |
22 | #include <TMath.h> | |
23 | ||
24 | #include "AliCascadeVertex.h" | |
25 | #include "AliV0vertex.h" | |
26 | #include "AliITStrackV2.h" | |
27 | ||
28 | ClassImp(AliCascadeVertex) | |
29 | ||
30 | AliCascadeVertex::AliCascadeVertex() : TObject() { | |
31 | //-------------------------------------------------------------------- | |
32 | // Default constructor (Xi-) | |
33 | //-------------------------------------------------------------------- | |
34 | fPdgCode=kXiMinus; | |
35 | fEffMass=1.32131; | |
36 | fChi2=1.e+33; | |
37 | fPos[0]=fPos[1]=fPos[2]=0.; | |
38 | fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.; | |
39 | } | |
40 | ||
41 | ||
42 | ||
43 | inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ | |
44 | // determinant 2x2 | |
45 | return a00*a11 - a01*a10; | |
46 | } | |
47 | ||
48 | inline Double_t det (Double_t a00,Double_t a01,Double_t a02, | |
49 | Double_t a10,Double_t a11,Double_t a12, | |
50 | Double_t a20,Double_t a21,Double_t a22) { | |
51 | // determinant 3x3 | |
52 | return | |
53 | a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); | |
54 | } | |
55 | ||
56 | ||
57 | ||
58 | AliCascadeVertex::AliCascadeVertex(const AliV0vertex &v,const AliITStrackV2 &t) { | |
59 | //-------------------------------------------------------------------- | |
60 | // Main constructor | |
61 | //-------------------------------------------------------------------- | |
62 | fPdgCode=kXiMinus; | |
63 | ||
64 | fV0lab[0]=v.GetNlabel(); fV0lab[1]=v.GetPlabel(); | |
65 | fBachLab=t.GetLabel(); | |
66 | ||
67 | //Trivial estimation of the vertex parameters | |
68 | Double_t pt, phi, x, par[5]; | |
69 | Double_t alpha, cs, sn; | |
70 | ||
71 | t.GetExternalParameters(x,par); alpha=t.GetAlpha(); | |
72 | pt=1./TMath::Abs(par[4]); | |
73 | phi=TMath::ASin(par[2]) + alpha; | |
74 | ||
75 | // momentum of the bachelor track | |
76 | ||
77 | Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3]; | |
78 | ||
79 | cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); | |
80 | ||
81 | Double_t x1=x*cs - par[0]*sn; // position of the bachelor at dca (bachelor,V0) | |
82 | Double_t y1=x*sn + par[0]*cs; | |
83 | Double_t z1=par[1]; | |
84 | ||
85 | Double_t x2,y2,z2; // position of the V0 | |
86 | v.GetXYZ(x2,y2,z2); | |
87 | ||
88 | Double_t px2,py2,pz2; // momentum of V0 | |
89 | v.GetPxPyPz(px2,py2,pz2); | |
90 | ||
91 | Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2); | |
92 | ||
93 | Double_t xm=x2+a2*px2; | |
94 | Double_t ym=y2+a2*py2; | |
95 | Double_t zm=z2+a2*pz2; | |
96 | ||
97 | // position of the cascade decay | |
98 | ||
99 | fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm); | |
100 | ||
101 | ||
102 | // momenta of the bachelor and the V0 | |
103 | ||
104 | fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1; | |
105 | fV0mom[0]=px2; fV0mom[1]=py2; fV0mom[2]=pz2; | |
106 | ||
107 | // invariant mass of the cascade (default is Ximinus) | |
108 | ||
109 | Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); | |
110 | Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2); | |
111 | ||
112 | fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- | |
113 | (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); | |
114 | ||
115 | fChi2=7.; | |
116 | ||
117 | } | |
118 | ||
119 | void AliCascadeVertex::ChangeMassHypothesis(Int_t code) { | |
120 | //-------------------------------------------------------------------- | |
121 | // This function changes the mass hypothesis for this cascade | |
122 | //-------------------------------------------------------------------- | |
123 | ||
124 | // HOW TO DISTINGUISH BETWEEN A XIMINUS AND A XIPLUS ?????????? | |
125 | // SAME QUESTION FOR (ANTI-)OMEGA'S (here) ... AND FOR (ANTI-)LAMBDAS (in AliV0vertex) ?? | |
126 | // -> NEED ADDITIONAL CONDITION ON BACHELOR AND V0 PDGCODE !!!! BUT in the ANALYSIS MACROS !!! | |
127 | ||
128 | Double_t massBach, massV0; | |
129 | ||
130 | switch (code) { | |
131 | ||
132 | case kXiMinus: | |
133 | massBach=0.13957; massV0=1.11568; break; | |
134 | case kXiPlusBar: | |
135 | massBach=0.13957; massV0=1.11568; break; | |
136 | case kOmegaMinus: | |
137 | massBach=0.49368; massV0=1.11568; break; | |
138 | case kOmegaPlusBar: | |
139 | massBach=0.49368; massV0=1.11568; break; | |
140 | ||
141 | default: | |
142 | cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; | |
143 | cerr<<"invalide PDG code ! Assuming XiMinus's...\n"; | |
144 | massBach=0.13957; massV0=1.11568; break; | |
145 | } | |
146 | ||
147 | Double_t px1=fBachMom[0], py1=fBachMom[1], pz1=fBachMom[2]; | |
148 | Double_t px2=fV0mom[0], py2=fV0mom[1], pz2=fV0mom[2]; | |
149 | ||
150 | Double_t e1=TMath::Sqrt(massBach*massBach + px1*px1 + py1*py1 + pz1*pz1); | |
151 | Double_t e2=TMath::Sqrt(massV0*massV0 + px2*px2 + py2*py2 + pz2*pz2); | |
152 | fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- | |
153 | (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); | |
154 | ||
155 | fPdgCode=code; | |
156 | } | |
157 | ||
158 | void | |
159 | AliCascadeVertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { | |
160 | //-------------------------------------------------------------------- | |
161 | // This function returns the cascade momentum (global) | |
162 | //-------------------------------------------------------------------- | |
163 | px=fV0mom[0]+fBachMom[0]; | |
164 | py=fV0mom[1]+fBachMom[1]; | |
165 | pz=fV0mom[2]+fBachMom[2]; | |
166 | } | |
167 | ||
168 | void AliCascadeVertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { | |
169 | //-------------------------------------------------------------------- | |
170 | // This function returns cascade position (global) | |
171 | //-------------------------------------------------------------------- | |
172 | x=fPos[0]; | |
173 | y=fPos[1]; | |
174 | z=fPos[2]; | |
175 | } | |
176 | ||
177 | Double_t AliCascadeVertex::GetD(Double_t x0, Double_t y0, Double_t z0) const { | |
178 | //-------------------------------------------------------------------- | |
179 | // This function returns the cascade impact parameter | |
180 | //-------------------------------------------------------------------- | |
181 | ||
182 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; | |
183 | Double_t px=fV0mom[0]+fBachMom[0]; | |
184 | Double_t py=fV0mom[1]+fBachMom[1]; | |
185 | Double_t pz=fV0mom[2]+fBachMom[2]; | |
186 | ||
187 | Double_t dx=(y0-y)*pz - (z0-z)*py; | |
188 | Double_t dy=(x0-x)*pz - (z0-z)*px; | |
189 | Double_t dz=(x0-x)*py - (y0-y)*px; | |
190 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); | |
191 | ||
192 | return d; | |
193 | } |