Introduction of ESD and combined PID
[u/mrichter/AliRoot.git] / ITS / AliCascadeVertex.cxx
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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//-------------------------------------------------------------------------
4ae5bbc4 21#include <Riostream.h>
a9a2d814 22#include <TMath.h>
116cbefd 23#include <TPDGCode.h>
a9a2d814 24
25#include "AliCascadeVertex.h"
a9a2d814 26#include "AliITStrackV2.h"
116cbefd 27#include "AliV0vertex.h"
a9a2d814 28
29ClassImp(AliCascadeVertex)
30
31AliCascadeVertex::AliCascadeVertex() : TObject() {
32 //--------------------------------------------------------------------
33 // Default constructor (Xi-)
34 //--------------------------------------------------------------------
35 fPdgCode=kXiMinus;
36 fEffMass=1.32131;
37 fChi2=1.e+33;
38 fPos[0]=fPos[1]=fPos[2]=0.;
39 fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.;
40}
41
42
43
44inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){
45 // determinant 2x2
46 return a00*a11 - a01*a10;
47}
48
49inline Double_t det (Double_t a00,Double_t a01,Double_t a02,
50 Double_t a10,Double_t a11,Double_t a12,
51 Double_t a20,Double_t a21,Double_t a22) {
52 // determinant 3x3
53 return
54 a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21);
55}
56
57
58
59AliCascadeVertex::AliCascadeVertex(const AliV0vertex &v,const AliITStrackV2 &t) {
60 //--------------------------------------------------------------------
61 // Main constructor
62 //--------------------------------------------------------------------
63 fPdgCode=kXiMinus;
64
65 fV0lab[0]=v.GetNlabel(); fV0lab[1]=v.GetPlabel();
66 fBachLab=t.GetLabel();
67
68 //Trivial estimation of the vertex parameters
69 Double_t pt, phi, x, par[5];
70 Double_t alpha, cs, sn;
71
72 t.GetExternalParameters(x,par); alpha=t.GetAlpha();
73 pt=1./TMath::Abs(par[4]);
74 phi=TMath::ASin(par[2]) + alpha;
75
76 // momentum of the bachelor track
77
78 Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3];
79
80 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
81
82 Double_t x1=x*cs - par[0]*sn; // position of the bachelor at dca (bachelor,V0)
83 Double_t y1=x*sn + par[0]*cs;
84 Double_t z1=par[1];
85
86 Double_t x2,y2,z2; // position of the V0
87 v.GetXYZ(x2,y2,z2);
88
89 Double_t px2,py2,pz2; // momentum of V0
90 v.GetPxPyPz(px2,py2,pz2);
91
92 Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2);
93
94 Double_t xm=x2+a2*px2;
95 Double_t ym=y2+a2*py2;
96 Double_t zm=z2+a2*pz2;
97
98 // position of the cascade decay
99
100 fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm);
04b2a5f1 101
102
a9a2d814 103 // invariant mass of the cascade (default is Ximinus)
104
105 Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1);
106 Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2);
107
108 fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)-
109 (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2));
110
04b2a5f1 111
112 // momenta of the bachelor and the V0
113
114 fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1;
115 v.GetNPxPyPz(px2,py2,pz2);
116 fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2;
117 v.GetPPxPyPz(px2,py2,pz2);
118 fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2;
119
120
a9a2d814 121 fChi2=7.;
122
123}
124
04b2a5f1 125/*
126Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) {
a9a2d814 127 //--------------------------------------------------------------------
128 // This function changes the mass hypothesis for this cascade
04b2a5f1 129 // and returns the "kinematical quality" of this hypothesis
130 // together with the "quality" of associated V0 (argument v0q)
a9a2d814 131 //--------------------------------------------------------------------
04b2a5f1 132 Double_t nmass=0.13957, pmass=0.93827, des0=0.9437-0.1723;
133 Double_t bmass=0.13957, mass =1.3213, des =1.1243-0.1970;
a9a2d814 134
04b2a5f1 135 fPdgCode=code;
a9a2d814 136
04b2a5f1 137 switch (code) {
138 case 213:
139 bmass=0.93827;
140 break;
a9a2d814 141 case kXiMinus:
04b2a5f1 142 break;
a9a2d814 143 case kXiPlusBar:
04b2a5f1 144 nmass=0.93827; pmass=0.13957; des0=-des0;
145 des=-des;
146 break;
a9a2d814 147 case kOmegaMinus:
04b2a5f1 148 bmass=0.49368; mass=1.67245; des=1.1355-0.5369;
149 break;
a9a2d814 150 case kOmegaPlusBar:
04b2a5f1 151 nmass=0.93827; pmass=0.13957; des0=-des0;
152 bmass=0.49368; mass=1.67245; des=0.5369-1.1355;
153 break;
a9a2d814 154 default:
04b2a5f1 155 cerr<<"AliCascadeVertex::ChangeMassHypothesis: ";
156 cerr<<"Invalide PDG code ! Assuming XiMinus's...\n";
157 fPdgCode=kXiMinus;
158 break;
a9a2d814 159 }
160
04b2a5f1 161 Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2];
162 Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2];
163 Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn);
164 Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp);
165 Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp;
166 Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0);
a9a2d814 167
04b2a5f1 168 Double_t gamma0=(en+ep)/1.11568, betagamma0=p0/1.11568;
169 Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0;
170 Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0;
171 Double_t plps=gamma0*plp - betagamma0*ep;
172
173 Double_t diff0=2*gamma0*plps + betagamma0*des0;
174
175
176 v0q=plp-pln-diff0;
177
178
179 Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2];
180
181 Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0);
182 Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb);
183 Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb;
184 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
a9a2d814 185
04b2a5f1 186 fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl);
187
188 Double_t gamma=(e0+eb)/mass, betagamma=pl/mass;
189 Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl;
190 Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl;
191 Double_t pl0s=gamma*pl0 - betagamma*e0;
192
193 Double_t diff=2*gamma*pl0s + betagamma*des;
194
195 return (pl0-plb-diff);
196}
197*/
198
199Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) {
200 //--------------------------------------------------------------------
201 // This function changes the mass hypothesis for this cascade
202 // and returns the "kinematical quality" of this hypothesis
203 // together with the "quality" of associated V0 (argument v0q)
204 //--------------------------------------------------------------------
205 Double_t nmass=0.13957, pmass=0.93827, ps0=0.101;
206 Double_t bmass=0.13957, mass =1.3213, ps =0.139;
207
a9a2d814 208 fPdgCode=code;
04b2a5f1 209
210 switch (code) {
211 case 213:
212 bmass=0.93827;
213 break;
214 case kXiMinus:
215 break;
216 case kXiPlusBar:
217 nmass=0.93827; pmass=0.13957;
218 break;
219 case kOmegaMinus:
220 bmass=0.49368; mass=1.67245; ps=0.211;
221 break;
222 case kOmegaPlusBar:
223 nmass=0.93827; pmass=0.13957;
224 bmass=0.49368; mass=1.67245; ps=0.211;
225 break;
226 default:
227 cerr<<"AliCascadeVertex::ChangeMassHypothesis: ";
228 cerr<<"Invalide PDG code ! Assuming XiMinus's...\n";
229 fPdgCode=kXiMinus;
230 break;
231 }
232
233 Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2];
234 Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2];
235 Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp;
236 Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0);
237
238 Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0);
239 Double_t beta0=p0/e0;
240 Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0;
241 Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0;
242 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
243
244 Double_t a=(plp-pln)/(plp+pln);
245 a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568);
246 a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2;
247
248
249 v0q=a - ps0*ps0;
250
251
252 Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2];
253
254 Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb);
255 Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb;
256 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
257
258 fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl);
259
260 Double_t beta=pl/(e0+eb);
261 Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl;
262 Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl;
263 pt2=p0*p0 - pl0*pl0;
264
265 a=(pl0-plb)/(pl0+plb);
266 a -= (1.11568*1.11568-bmass*bmass)/(mass*mass);
267 a = 0.25*beta*beta*mass*mass*a*a + pt2;
268
269 return (a - ps*ps);
a9a2d814 270}
271
272void
273AliCascadeVertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
274 //--------------------------------------------------------------------
275 // This function returns the cascade momentum (global)
276 //--------------------------------------------------------------------
04b2a5f1 277 px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
278 py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
279 pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
a9a2d814 280}
281
282void AliCascadeVertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
283 //--------------------------------------------------------------------
284 // This function returns cascade position (global)
285 //--------------------------------------------------------------------
286 x=fPos[0];
287 y=fPos[1];
288 z=fPos[2];
289}
290
291Double_t AliCascadeVertex::GetD(Double_t x0, Double_t y0, Double_t z0) const {
292 //--------------------------------------------------------------------
293 // This function returns the cascade impact parameter
294 //--------------------------------------------------------------------
295
296 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
04b2a5f1 297 Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
298 Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
299 Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
a9a2d814 300
301 Double_t dx=(y0-y)*pz - (z0-z)*py;
302 Double_t dy=(x0-x)*pz - (z0-z)*px;
303 Double_t dz=(x0-x)*py - (y0-y)*px;
304 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));
305
306 return d;
307}
04b2a5f1 308