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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 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); |
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100 | |
101 | |
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102 | // invariant mass of the cascade (default is Ximinus) |
103 | |
104 | Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); |
105 | Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2); |
106 | |
107 | fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- |
108 | (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); |
109 | |
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110 | |
111 | // momenta of the bachelor and the V0 |
112 | |
113 | fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1; |
114 | v.GetNPxPyPz(px2,py2,pz2); |
115 | fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2; |
116 | v.GetPPxPyPz(px2,py2,pz2); |
117 | fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2; |
118 | |
119 | |
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120 | fChi2=7.; |
121 | |
122 | } |
123 | |
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124 | /* |
125 | Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) { |
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126 | //-------------------------------------------------------------------- |
127 | // This function changes the mass hypothesis for this cascade |
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128 | // and returns the "kinematical quality" of this hypothesis |
129 | // together with the "quality" of associated V0 (argument v0q) |
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130 | //-------------------------------------------------------------------- |
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131 | Double_t nmass=0.13957, pmass=0.93827, des0=0.9437-0.1723; |
132 | Double_t bmass=0.13957, mass =1.3213, des =1.1243-0.1970; |
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133 | |
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134 | fPdgCode=code; |
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135 | |
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136 | switch (code) { |
137 | case 213: |
138 | bmass=0.93827; |
139 | break; |
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140 | case kXiMinus: |
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141 | break; |
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142 | case kXiPlusBar: |
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143 | nmass=0.93827; pmass=0.13957; des0=-des0; |
144 | des=-des; |
145 | break; |
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146 | case kOmegaMinus: |
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147 | bmass=0.49368; mass=1.67245; des=1.1355-0.5369; |
148 | break; |
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149 | case kOmegaPlusBar: |
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150 | nmass=0.93827; pmass=0.13957; des0=-des0; |
151 | bmass=0.49368; mass=1.67245; des=0.5369-1.1355; |
152 | break; |
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153 | default: |
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154 | cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; |
155 | cerr<<"Invalide PDG code ! Assuming XiMinus's...\n"; |
156 | fPdgCode=kXiMinus; |
157 | break; |
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158 | } |
159 | |
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160 | Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2]; |
161 | Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2]; |
162 | Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); |
163 | Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); |
164 | Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp; |
165 | Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0); |
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166 | |
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167 | Double_t gamma0=(en+ep)/1.11568, betagamma0=p0/1.11568; |
168 | Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0; |
169 | Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0; |
170 | Double_t plps=gamma0*plp - betagamma0*ep; |
171 | |
172 | Double_t diff0=2*gamma0*plps + betagamma0*des0; |
173 | |
174 | |
175 | v0q=plp-pln-diff0; |
176 | |
177 | |
178 | Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2]; |
179 | |
180 | Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0); |
181 | Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb); |
182 | Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb; |
183 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); |
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184 | |
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185 | fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl); |
186 | |
187 | Double_t gamma=(e0+eb)/mass, betagamma=pl/mass; |
188 | Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl; |
189 | Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl; |
190 | Double_t pl0s=gamma*pl0 - betagamma*e0; |
191 | |
192 | Double_t diff=2*gamma*pl0s + betagamma*des; |
193 | |
194 | return (pl0-plb-diff); |
195 | } |
196 | */ |
197 | |
198 | Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) { |
199 | //-------------------------------------------------------------------- |
200 | // This function changes the mass hypothesis for this cascade |
201 | // and returns the "kinematical quality" of this hypothesis |
202 | // together with the "quality" of associated V0 (argument v0q) |
203 | //-------------------------------------------------------------------- |
204 | Double_t nmass=0.13957, pmass=0.93827, ps0=0.101; |
205 | Double_t bmass=0.13957, mass =1.3213, ps =0.139; |
206 | |
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207 | fPdgCode=code; |
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208 | |
209 | switch (code) { |
210 | case 213: |
211 | bmass=0.93827; |
212 | break; |
213 | case kXiMinus: |
214 | break; |
215 | case kXiPlusBar: |
216 | nmass=0.93827; pmass=0.13957; |
217 | break; |
218 | case kOmegaMinus: |
219 | bmass=0.49368; mass=1.67245; ps=0.211; |
220 | break; |
221 | case kOmegaPlusBar: |
222 | nmass=0.93827; pmass=0.13957; |
223 | bmass=0.49368; mass=1.67245; ps=0.211; |
224 | break; |
225 | default: |
226 | cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; |
227 | cerr<<"Invalide PDG code ! Assuming XiMinus's...\n"; |
228 | fPdgCode=kXiMinus; |
229 | break; |
230 | } |
231 | |
232 | Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2]; |
233 | Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2]; |
234 | Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp; |
235 | Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0); |
236 | |
237 | Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0); |
238 | Double_t beta0=p0/e0; |
239 | Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0; |
240 | Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0; |
241 | Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; |
242 | |
243 | Double_t a=(plp-pln)/(plp+pln); |
244 | a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568); |
245 | a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2; |
246 | |
247 | |
248 | v0q=a - ps0*ps0; |
249 | |
250 | |
251 | Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2]; |
252 | |
253 | Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb); |
254 | Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb; |
255 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); |
256 | |
257 | fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl); |
258 | |
259 | Double_t beta=pl/(e0+eb); |
260 | Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl; |
261 | Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl; |
262 | pt2=p0*p0 - pl0*pl0; |
263 | |
264 | a=(pl0-plb)/(pl0+plb); |
265 | a -= (1.11568*1.11568-bmass*bmass)/(mass*mass); |
266 | a = 0.25*beta*beta*mass*mass*a*a + pt2; |
267 | |
268 | return (a - ps*ps); |
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269 | } |
270 | |
271 | void |
272 | AliCascadeVertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { |
273 | //-------------------------------------------------------------------- |
274 | // This function returns the cascade momentum (global) |
275 | //-------------------------------------------------------------------- |
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276 | px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; |
277 | py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; |
278 | pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2]; |
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279 | } |
280 | |
281 | void AliCascadeVertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { |
282 | //-------------------------------------------------------------------- |
283 | // This function returns cascade position (global) |
284 | //-------------------------------------------------------------------- |
285 | x=fPos[0]; |
286 | y=fPos[1]; |
287 | z=fPos[2]; |
288 | } |
289 | |
290 | Double_t AliCascadeVertex::GetD(Double_t x0, Double_t y0, Double_t z0) const { |
291 | //-------------------------------------------------------------------- |
292 | // This function returns the cascade impact parameter |
293 | //-------------------------------------------------------------------- |
294 | |
295 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; |
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296 | Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; |
297 | Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; |
298 | Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2]; |
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299 | |
300 | Double_t dx=(y0-y)*pz - (z0-z)*py; |
301 | Double_t dy=(x0-x)*pz - (z0-z)*px; |
302 | Double_t dz=(x0-x)*py - (y0-y)*px; |
303 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); |
304 | |
305 | return d; |
306 | } |
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307 | |