Update of material budget and positions
[u/mrichter/AliRoot.git] / STEER / AliESDcascade.cxx
CommitLineData
e23730c7 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
4f679a16 16/* $Id$ */
17
e23730c7 18//-------------------------------------------------------------------------
19// Implementation of the cascade vertex class
4f679a16 20// This is part of the Event Summary Data
21// which contains the result of the reconstruction
22// and is the main set of classes for analaysis
e23730c7 23// Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr
24//-------------------------------------------------------------------------
4f679a16 25
90e48c0c 26#include <TDatabasePDG.h>
e23730c7 27#include <TMath.h>
28
5f7789fc 29#include "AliLog.h"
c7bafca9 30#include "AliExternalTrackParam.h"
31#include "AliESDv0.h"
e23730c7 32#include "AliESDcascade.h"
e23730c7 33
34ClassImp(AliESDcascade)
35
90e48c0c 36AliESDcascade::AliESDcascade() :
37 TObject(),
38 fPdgCode(kXiMinus),
39 fEffMass(TDatabasePDG::Instance()->GetParticle(kXiMinus)->Mass()),
40 fChi2(1.e+33),
bfb36bff 41 fBachIdx(-1)
90e48c0c 42{
e23730c7 43 //--------------------------------------------------------------------
44 // Default constructor (Xi-)
45 //--------------------------------------------------------------------
bfb36bff 46 for (Int_t j=0; j<3; j++) {
47 fPos[j]=0.;
48 fBachMom[j]=0.;
49 }
50
51 for (Int_t i=0; i<2; i++)
52 for (Int_t j=0; j<3; j++)
53 fV0mom[i][j]=0.;
54
55 fV0idx[0]=fV0idx[1]=-1;
56
57 fPosCov[0]=1e10;
58 fPosCov[1]=fPosCov[2]=0.;
59 fPosCov[3]=1e10;
60 fPosCov[4]=0.;
61 fPosCov[5]=1e10;
62
63 fV0momCov[0]=1e10;
64 fV0momCov[1]=fV0momCov[2]=0.;
65 fV0momCov[3]=1e10;
66 fV0momCov[4]=0.;
67 fV0momCov[5]=1e10;
68
69 fBachMomCov[0]=1e10;
70 fBachMomCov[1]=fBachMomCov[2]=0.;
71 fBachMomCov[3]=1e10;
72 fBachMomCov[4]=0.;
73 fBachMomCov[5]=1e10;
e23730c7 74}
75
c7bafca9 76AliESDcascade::AliESDcascade(const AliESDv0 &v,
77 const AliExternalTrackParam &t, Int_t i) :
78 TObject(),
79 fPdgCode(kXiMinus),
80 fEffMass(TDatabasePDG::Instance()->GetParticle(kXiMinus)->Mass()),
81 fChi2(1.e+33),
82 fBachIdx(i)
83{
84 //--------------------------------------------------------------------
85 // Main constructor (Xi-)
86 //--------------------------------------------------------------------
87
88 fV0idx[0]=v.GetNindex(); fV0idx[1]=v.GetPindex();
89
90 Double_t r[3]; t.GetXYZ(r);
91 Double_t x1=r[0], y1=r[1], z1=r[2]; // position of the bachelor
92 Double_t p[3]; t.GetPxPyPz(p);
93 Double_t px1=p[0], py1=p[1], pz1=p[2];// momentum of the bachelor track
94
95 Double_t x2,y2,z2; // position of the V0
96 v.GetXYZ(x2,y2,z2);
97 Double_t px2,py2,pz2; // momentum of V0
98 v.GetPxPyPz(px2,py2,pz2);
99
100 Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2);
101
102 Double_t xm=x2+a2*px2;
103 Double_t ym=y2+a2*py2;
104 Double_t zm=z2+a2*pz2;
105
106 // position of the cascade decay
107
108 fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm);
109
110
111 // invariant mass of the cascade (default is Ximinus)
112
113 Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1);
114 Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2);
115
116 fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)-
117 (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2));
118
119
120 // momenta of the bachelor and the V0
121
122 fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1;
123 v.GetNPxPyPz(px2,py2,pz2);
124 fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2;
125 v.GetPPxPyPz(px2,py2,pz2);
126 fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2;
127
bfb36bff 128 //PH Covariance matrices: to be calculated correctly in the future
129 fPosCov[0]=1e10;
130 fPosCov[1]=fPosCov[2]=0.;
131 fPosCov[3]=1e10;
132 fPosCov[4]=0.;
133 fPosCov[5]=1e10;
134
135 fV0momCov[0]=1e10;
136 fV0momCov[1]=fV0momCov[2]=0.;
137 fV0momCov[3]=1e10;
138 fV0momCov[4]=0.;
139 fV0momCov[5]=1e10;
140
141 fBachMomCov[0]=1e10;
142 fBachMomCov[1]=fBachMomCov[2]=0.;
143 fBachMomCov[3]=1e10;
144 fBachMomCov[4]=0.;
145 fBachMomCov[5]=1e10;
c7bafca9 146
147 fChi2=7.;
148
149}
150
e23730c7 151Double_t AliESDcascade::ChangeMassHypothesis(Double_t &v0q, Int_t code) {
152 //--------------------------------------------------------------------
153 // This function changes the mass hypothesis for this cascade
154 // and returns the "kinematical quality" of this hypothesis
155 // together with the "quality" of associated V0 (argument v0q)
156 //--------------------------------------------------------------------
157 Double_t nmass=0.13957, pmass=0.93827, ps0=0.101;
158 Double_t bmass=0.13957, mass =1.3213, ps =0.139;
159
160 fPdgCode=code;
161
162 switch (code) {
163 case 213:
164 bmass=0.93827;
165 break;
166 case kXiMinus:
167 break;
168 case kXiPlusBar:
169 nmass=0.93827; pmass=0.13957;
170 break;
171 case kOmegaMinus:
172 bmass=0.49368; mass=1.67245; ps=0.211;
173 break;
174 case kOmegaPlusBar:
175 nmass=0.93827; pmass=0.13957;
176 bmass=0.49368; mass=1.67245; ps=0.211;
177 break;
178 default:
5f7789fc 179 AliError("Invalide PDG code ! Assuming XiMinus's...");
e23730c7 180 fPdgCode=kXiMinus;
181 break;
182 }
183
184 Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2];
185 Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2];
186 Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp;
187 Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0);
188
189 Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0);
190 Double_t beta0=p0/e0;
191 Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0;
192 Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0;
193 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
194
195 Double_t a=(plp-pln)/(plp+pln);
196 a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568);
197 a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2;
198
199
200 v0q=a - ps0*ps0;
201
202
203 Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2];
204
205 Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb);
206 Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb;
207 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
208
209 fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl);
210
211 Double_t beta=pl/(e0+eb);
212 Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl;
213 Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl;
214 pt2=p0*p0 - pl0*pl0;
215
216 a=(pl0-plb)/(pl0+plb);
217 a -= (1.11568*1.11568-bmass*bmass)/(mass*mass);
218 a = 0.25*beta*beta*mass*mass*a*a + pt2;
219
220 return (a - ps*ps);
221}
222
223void
224AliESDcascade::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
225 //--------------------------------------------------------------------
226 // This function returns the cascade momentum (global)
227 //--------------------------------------------------------------------
228 px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
229 py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
230 pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
231}
232
233void AliESDcascade::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
234 //--------------------------------------------------------------------
235 // This function returns cascade position (global)
236 //--------------------------------------------------------------------
237 x=fPos[0];
238 y=fPos[1];
239 z=fPos[2];
240}
241
242Double_t AliESDcascade::GetD(Double_t x0, Double_t y0, Double_t z0) const {
243 //--------------------------------------------------------------------
244 // This function returns the cascade impact parameter
245 //--------------------------------------------------------------------
246
247 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
248 Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
249 Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
250 Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
251
252 Double_t dx=(y0-y)*pz - (z0-z)*py;
253 Double_t dy=(x0-x)*pz - (z0-z)*px;
254 Double_t dz=(x0-x)*py - (y0-y)*px;
255 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));
256
257 return d;
258}
259