Updated code/macros to be compliant with the current HEAD (from Y. Belikov)
[u/mrichter/AliRoot.git] / ITS / AliV0vertex.cxx
CommitLineData
7f6ddf58 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 V0 vertex class
18//
19// Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch
20//-------------------------------------------------------------------------
21#include <iostream.h>
22#include <TMath.h>
23
24#include "AliV0vertex.h"
25#include "AliITStrackV2.h"
26
27ClassImp(AliV0vertex)
28
29AliV0vertex::AliV0vertex() : TObject() {
30 //--------------------------------------------------------------------
31 // Default constructor (K0s)
32 //--------------------------------------------------------------------
33 fPdgCode=kK0Short;
34 fEffMass=0.497672;
35 fChi2=1.e+33;
36 fPos[0]=fPos[1]=fPos[2]=0.;
37 fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.;
38}
39
40AliV0vertex::AliV0vertex(const AliITStrackV2 &n, const AliITStrackV2 &p) {
41 //--------------------------------------------------------------------
42 // Main constructor
43 //--------------------------------------------------------------------
44 fPdgCode=kK0Short;
45 fNlab=n.GetLabel(); fPlab=p.GetLabel();
46
47 //Trivial estimation of the vertex parameters
48 Double_t pt, phi, x, par[5];
49 Double_t alpha, cs, sn;
50
51 n.GetExternalParameters(x,par); alpha=n.GetAlpha();
52 pt=1./TMath::Abs(par[4]);
53 phi=TMath::ASin(par[2]) + alpha;
54 Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3];
55 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
56 Double_t x1=x*cs - par[0]*sn;
57 Double_t y1=x*sn + par[0]*cs;
58 Double_t z1=par[1];
59 Double_t sx1=sn*sn*n.GetSigmaY2(), sy1=cs*cs*n.GetSigmaY2();
60
61 p.GetExternalParameters(x,par); alpha=p.GetAlpha();
62 pt=1./TMath::Abs(par[4]);
63 phi=TMath::ASin(par[2]) + alpha;
64 Double_t px2=pt*TMath::Cos(phi), py2=pt*TMath::Sin(phi), pz2=pt*par[3];
65 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
66 Double_t x2=x*cs - par[0]*sn;
67 Double_t y2=x*sn + par[0]*cs;
68 Double_t z2=par[1];
69 Double_t sx2=sn*sn*p.GetSigmaY2(), sy2=cs*cs*p.GetSigmaY2();
70
71 Double_t sz1=n.GetSigmaZ2(), sz2=p.GetSigmaZ2();
72 Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1;
73 Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1;
74 Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1;
75 fPos[0]=wx1*x1 + wx2*x2; fPos[1]=wy1*y1 + wy2*y2; fPos[2]=wz1*z1 + wz2*z2;
76
77 //fPos[0]=0.5*(x1+x2); fPos[1]=0.5*(y1+y2); fPos[2]=0.5*(z1+z2);
78 fNmom[0]=px1; fNmom[1]=py1; fNmom[2]=pz1;
79 fPmom[0]=px2; fPmom[1]=py2; fPmom[2]=pz2;
80
81 Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1);
82 Double_t e2=TMath::Sqrt(0.13957*0.13957 + px2*px2 + py2*py2 + pz2*pz2);
83 fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)-
84 (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2));
85
86 fChi2=7.;
87}
04b2a5f1 88/*
89Double_t AliV0vertex::ChangeMassHypothesis(Int_t code) {
7f6ddf58 90 //--------------------------------------------------------------------
91 // This function changes the mass hypothesis for this V0
04b2a5f1 92 // and returns the "kinematical quality" of this hypothesis
7f6ddf58 93 //--------------------------------------------------------------------
04b2a5f1 94 Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, des=0;
95
96 fPdgCode=code;
7f6ddf58 97
98 switch (code) {
99 case kLambda0:
04b2a5f1 100 nmass=0.13957; pmass=0.93827; mass=1.1157; des=0.9437-0.1723; break;
7f6ddf58 101 case kLambda0Bar:
04b2a5f1 102 pmass=0.13957; nmass=0.93827; mass=1.1157; des=0.1723-0.9437; break;
7f6ddf58 103 case kK0Short:
04b2a5f1 104 break;
7f6ddf58 105 default:
106 cerr<<"AliV0vertex::ChangeMassHypothesis: ";
107 cerr<<"invalide PDG code ! Assuming K0s...\n";
04b2a5f1 108 fPdgCode=kK0Short;
109 break;
7f6ddf58 110 }
111
04b2a5f1 112 Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2];
113 Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2];
7f6ddf58 114
04b2a5f1 115 Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn);
116 Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp);
117 Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp;
118 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
119
120 fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl);
121
122 Double_t gamma=(en+ep)/mass, betagamma=pl/mass;
123 Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl;
124 Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl;
125 Double_t plps=gamma*plp - betagamma*ep;
126
127 Double_t diff=2*gamma*plps + betagamma*des;
128
129 return (plp-pln-diff);
7f6ddf58 130
04b2a5f1 131}
132*/
133Double_t AliV0vertex::ChangeMassHypothesis(Int_t code) {
134 //--------------------------------------------------------------------
135 // This function changes the mass hypothesis for this V0
136 // and returns the "kinematical quality" of this hypothesis
137 //--------------------------------------------------------------------
138 Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206;
139
7f6ddf58 140 fPdgCode=code;
04b2a5f1 141
142 switch (code) {
143 case kLambda0:
144 nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break;
145 case kLambda0Bar:
146 pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break;
147 case kK0Short:
148 break;
149 default:
150 cerr<<"AliV0vertex::ChangeMassHypothesis: ";
151 cerr<<"invalide PDG code ! Assuming K0s...\n";
152 fPdgCode=kK0Short;
153 break;
154 }
155
156 Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2];
157 Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2];
158
159 Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn);
160 Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp);
161 Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp;
162 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
163
164 fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl);
165
166 Double_t beta=pl/(en+ep);
167 Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl;
168 Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl;
169
170 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
171
172 Double_t a=(plp-pln)/(plp+pln);
173 a -= (pmass*pmass-nmass*nmass)/(mass*mass);
174 a = 0.25*beta*beta*mass*mass*a*a + pt2;
175
176 return (a - ps*ps);
177
7f6ddf58 178}
179
180void AliV0vertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
181 //--------------------------------------------------------------------
182 // This function returns V0's momentum (global)
183 //--------------------------------------------------------------------
184 px=fNmom[0]+fPmom[0];
185 py=fNmom[1]+fPmom[1];
186 pz=fNmom[2]+fPmom[2];
187}
188
189void AliV0vertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
190 //--------------------------------------------------------------------
191 // This function returns V0's position (global)
192 //--------------------------------------------------------------------
193 x=fPos[0];
194 y=fPos[1];
195 z=fPos[2];
196}
197
198Double_t AliV0vertex::GetD(Double_t x0, Double_t y0, Double_t z0) const {
199 //--------------------------------------------------------------------
200 // This function returns V0's impact parameter
201 //--------------------------------------------------------------------
202 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
203 Double_t px=fNmom[0]+fPmom[0];
204 Double_t py=fNmom[1]+fPmom[1];
205 Double_t pz=fNmom[2]+fPmom[2];
206
207 Double_t dx=(y0-y)*pz - (z0-z)*py;
208 Double_t dy=(x0-x)*pz - (z0-z)*px;
209 Double_t dz=(x0-x)*py - (y0-y)*px;
210 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));
211 return d;
212}