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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); | |
04b2a5f1 | 100 | |
101 | ||
a9a2d814 | 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 | ||
04b2a5f1 | 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 | ||
a9a2d814 | 120 | fChi2=7.; |
121 | ||
122 | } | |
123 | ||
04b2a5f1 | 124 | /* |
125 | Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) { | |
a9a2d814 | 126 | //-------------------------------------------------------------------- |
127 | // This function changes the mass hypothesis for this cascade | |
04b2a5f1 | 128 | // and returns the "kinematical quality" of this hypothesis |
129 | // together with the "quality" of associated V0 (argument v0q) | |
a9a2d814 | 130 | //-------------------------------------------------------------------- |
04b2a5f1 | 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; | |
a9a2d814 | 133 | |
04b2a5f1 | 134 | fPdgCode=code; |
a9a2d814 | 135 | |
04b2a5f1 | 136 | switch (code) { |
137 | case 213: | |
138 | bmass=0.93827; | |
139 | break; | |
a9a2d814 | 140 | case kXiMinus: |
04b2a5f1 | 141 | break; |
a9a2d814 | 142 | case kXiPlusBar: |
04b2a5f1 | 143 | nmass=0.93827; pmass=0.13957; des0=-des0; |
144 | des=-des; | |
145 | break; | |
a9a2d814 | 146 | case kOmegaMinus: |
04b2a5f1 | 147 | bmass=0.49368; mass=1.67245; des=1.1355-0.5369; |
148 | break; | |
a9a2d814 | 149 | case kOmegaPlusBar: |
04b2a5f1 | 150 | nmass=0.93827; pmass=0.13957; des0=-des0; |
151 | bmass=0.49368; mass=1.67245; des=0.5369-1.1355; | |
152 | break; | |
a9a2d814 | 153 | default: |
04b2a5f1 | 154 | cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; |
155 | cerr<<"Invalide PDG code ! Assuming XiMinus's...\n"; | |
156 | fPdgCode=kXiMinus; | |
157 | break; | |
a9a2d814 | 158 | } |
159 | ||
04b2a5f1 | 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); | |
a9a2d814 | 166 | |
04b2a5f1 | 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); | |
a9a2d814 | 184 | |
04b2a5f1 | 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 | ||
a9a2d814 | 207 | fPdgCode=code; |
04b2a5f1 | 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); | |
a9a2d814 | 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 | //-------------------------------------------------------------------- | |
04b2a5f1 | 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]; | |
a9a2d814 | 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]; | |
04b2a5f1 | 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]; | |
a9a2d814 | 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 | } | |
04b2a5f1 | 307 |