AliESDVertex is no longer written on the ESD: this was a side effect of FindVertexFor...
[u/mrichter/AliRoot.git] / STEER / AliESDcascade.cxx
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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),
41 fBachIdx(0)
42{
e23730c7 43 //--------------------------------------------------------------------
44 // Default constructor (Xi-)
45 //--------------------------------------------------------------------
e23730c7 46 fPos[0]=fPos[1]=fPos[2]=0.;
47 fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.;
48}
49
c7bafca9 50AliESDcascade::AliESDcascade(const AliESDv0 &v,
51 const AliExternalTrackParam &t, Int_t i) :
52 TObject(),
53 fPdgCode(kXiMinus),
54 fEffMass(TDatabasePDG::Instance()->GetParticle(kXiMinus)->Mass()),
55 fChi2(1.e+33),
56 fBachIdx(i)
57{
58 //--------------------------------------------------------------------
59 // Main constructor (Xi-)
60 //--------------------------------------------------------------------
61
62 fV0idx[0]=v.GetNindex(); fV0idx[1]=v.GetPindex();
63
64 Double_t r[3]; t.GetXYZ(r);
65 Double_t x1=r[0], y1=r[1], z1=r[2]; // position of the bachelor
66 Double_t p[3]; t.GetPxPyPz(p);
67 Double_t px1=p[0], py1=p[1], pz1=p[2];// momentum of the bachelor track
68
69 Double_t x2,y2,z2; // position of the V0
70 v.GetXYZ(x2,y2,z2);
71 Double_t px2,py2,pz2; // momentum of V0
72 v.GetPxPyPz(px2,py2,pz2);
73
74 Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2);
75
76 Double_t xm=x2+a2*px2;
77 Double_t ym=y2+a2*py2;
78 Double_t zm=z2+a2*pz2;
79
80 // position of the cascade decay
81
82 fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm);
83
84
85 // invariant mass of the cascade (default is Ximinus)
86
87 Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1);
88 Double_t e2=TMath::Sqrt(1.11568*1.11568 + px2*px2 + py2*py2 + pz2*pz2);
89
90 fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)-
91 (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2));
92
93
94 // momenta of the bachelor and the V0
95
96 fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1;
97 v.GetNPxPyPz(px2,py2,pz2);
98 fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2;
99 v.GetPPxPyPz(px2,py2,pz2);
100 fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2;
101
102
103 fChi2=7.;
104
105}
106
e23730c7 107Double_t AliESDcascade::ChangeMassHypothesis(Double_t &v0q, Int_t code) {
108 //--------------------------------------------------------------------
109 // This function changes the mass hypothesis for this cascade
110 // and returns the "kinematical quality" of this hypothesis
111 // together with the "quality" of associated V0 (argument v0q)
112 //--------------------------------------------------------------------
113 Double_t nmass=0.13957, pmass=0.93827, ps0=0.101;
114 Double_t bmass=0.13957, mass =1.3213, ps =0.139;
115
116 fPdgCode=code;
117
118 switch (code) {
119 case 213:
120 bmass=0.93827;
121 break;
122 case kXiMinus:
123 break;
124 case kXiPlusBar:
125 nmass=0.93827; pmass=0.13957;
126 break;
127 case kOmegaMinus:
128 bmass=0.49368; mass=1.67245; ps=0.211;
129 break;
130 case kOmegaPlusBar:
131 nmass=0.93827; pmass=0.13957;
132 bmass=0.49368; mass=1.67245; ps=0.211;
133 break;
134 default:
5f7789fc 135 AliError("Invalide PDG code ! Assuming XiMinus's...");
e23730c7 136 fPdgCode=kXiMinus;
137 break;
138 }
139
140 Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2];
141 Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2];
142 Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp;
143 Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0);
144
145 Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0);
146 Double_t beta0=p0/e0;
147 Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0;
148 Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0;
149 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
150
151 Double_t a=(plp-pln)/(plp+pln);
152 a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568);
153 a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2;
154
155
156 v0q=a - ps0*ps0;
157
158
159 Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2];
160
161 Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb);
162 Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb;
163 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
164
165 fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl);
166
167 Double_t beta=pl/(e0+eb);
168 Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl;
169 Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl;
170 pt2=p0*p0 - pl0*pl0;
171
172 a=(pl0-plb)/(pl0+plb);
173 a -= (1.11568*1.11568-bmass*bmass)/(mass*mass);
174 a = 0.25*beta*beta*mass*mass*a*a + pt2;
175
176 return (a - ps*ps);
177}
178
179void
180AliESDcascade::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
181 //--------------------------------------------------------------------
182 // This function returns the cascade momentum (global)
183 //--------------------------------------------------------------------
184 px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
185 py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
186 pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
187}
188
189void AliESDcascade::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
190 //--------------------------------------------------------------------
191 // This function returns cascade position (global)
192 //--------------------------------------------------------------------
193 x=fPos[0];
194 y=fPos[1];
195 z=fPos[2];
196}
197
198Double_t AliESDcascade::GetD(Double_t x0, Double_t y0, Double_t z0) const {
199 //--------------------------------------------------------------------
200 // This function returns the cascade impact parameter
201 //--------------------------------------------------------------------
202
203 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
204 Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0];
205 Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1];
206 Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2];
207
208 Double_t dx=(y0-y)*pz - (z0-z)*py;
209 Double_t dy=(x0-x)*pz - (z0-z)*px;
210 Double_t dz=(x0-x)*py - (y0-y)*px;
211 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));
212
213 return d;
214}
215